1980 mosaics 1 rome eng 8622 light

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d e te rio ra tio n a n c o n se rv tio n o m e n ov em b er 9 7 7



This report was published by the International Centre for the Study of the Preservationand the Restoration of Cultural Property, (lCCROM), 13 Via di San Michele, Rome.The layout was done by Veronigue Demaret.Forrest Selvig edited this English edition.



ACKNOWLEDGMENTS

This volume contains the proceedings of the First International Sym-posium on the Conservation of Mosaics which was held in Rome from2 to 5 November 1977. It was produced by the collaboration of thefollowing persons:

Patricia Bonicatti

Veronique DemaretGael de GuichenSusan InmanPatricia JohnsonCynthia RockwellForrest Selvig

The Symposium was made possible by grants generously given byUNESCO, the Direction des Musees de France and the Goethe-Institut.

On behalf of all the participants, we would like to express our sinceregratitude to all those who made this symposium possible.

ICCROM



FOR EWO RD

A s an in te r-gove rnm ental or ganiza tio n entru st ed with th e con ser vation an d r estora tio n of c ultu ral pr ope rty, IC CR OM is h appy to h ave c on ceived and org aniz ed th is F irst I ntern atio nal S ymp osiu m o n the Co nser vatio n ofMos a ics. Ind e ed, in a lm ost e ve ry cou nt ry that w as form e rly par t of thea ncient R oman w o rld, wal l or pave m ent mo s aics are often po orly mai n-tained aft er the ir di scove ry. This l ead s to th e r apid d isa ppear anc e of u niq uep arts o f ou r patr imo ny.

Aw areness o f this p ro blem iš n ecess ar y at all le ve s:

on the te ch nical l eve l so t ha t cons erv ators sh aretheir ex perien ce s and cri ticize an d impr ov e, if n ece ssary ,ol der m eth ods a nd techn iqu es;

a mong ar chaeolog ists so t h at they recogniz e • thata new ly di scov ered mos aic is a m osa ic in dan geran d tha t the ir du ty to ward it d oes not e nd w ith scho larly study a n d public a tion. Co nservati o n is sur e ly oneof t he archa eo logist' s d uties. T hough it may be d ifficult, it is no less im perative ;

amon g admin istrators who mus t underst and the i m portanc eo f this p a trimony , be inte r ested i n it, and b udget

adequ ately for its conse rvation;o n the p u blic lev el so tha t s peciali st s respo n siblefor c on servat io n receiv e suppo rt from bo th group san d individ u als. It is the pub lic, 'after a ll, that b enefitsan d is se rv ed by the world -w ide co nse rvatio n m ovem en t.

We da re ho pe that e ac h par tic ipant, up on re tu rning to his ow n country, will work to sprea d the id e as that h ave bee n excha n ged at t h ism ee ting, and that, in t his w ay,t he m osa ics di sco vered wi ll be t ran smitte dint act to f ut ure gen e rations .

Bern ard M. Fe ilde n,D irec tor, IC CR OM1 Septem b er 1978



Sou r ces o f illu s trati on s

All p hoto grap h s w e re f u rnis h ed b y the auth ors o f the r es pe cti ve pa pe rs ex ce pt fo r th e fo llo win g: pa p er by Ir ina An dr ee scu , 1 , p lat e, Arc hi vio di St ato , V en ice , 2 an d11, p late s, Die tm ar S aret z , 3 - 8 , pla t es, S opri n tend e nza a i Mo nume nti, T rieste , 9, p late, Colle ction Chre t ienne etB yzan tine, E cole Pra ti que d es H a ute s Etud es, P aris, 1 0,

pla te , E. R itter , 12, D ietz-D emu s , Byz a ntin e Mos a ics, fig 67 ,13 a nd 16 , plat e s, M . Skia d ares is, 14 a nd 1 5 , Eco le Pr a tique d es H aute s Etu d es, P aris , from Die tz -De m us, o p cit figs. 8 9 - 90 ; pap e r by P aul P hjlipp ot. ph otogr a phs furnis h edb y Ga el de G uic he n; pa pe r b y C ir o R ob ot ti, an d c ov er ,A rc hivi o, So pr inte nd en za Arc h eolo g ica di Os tia .



LIST OF PARTICIPANTS

Maria Luisa Abreu Nunes Conservation technician,Museu Nacional de Arqueologia e Etnologia,R. Tenente Ferreira Durao, 55 - 3 Esq.,Lisbon, Portugal

Margaret Alexander rofessor and Co-Director,Corpus of the Mosaics of Tunis,Department of Classics,University of Iowa,Iowa City, Iowa 52242, U.S.A.

lrina Andreescu ssistant Professor of Byzantine Archaeology,Center for Byzantine Studies,Dumbarton Oaks,1703 Thirty-second Street N.W.,Washington, D.C. 20007, U.S.A.

Elisabetta Anselmi estorer,Istituto Centrale del Restauro,Piazza San Francesco di Paola 9,00186 Rome, Italy

Vincenzo Antonelli oprintendenza Beni Ambientalied Architettonici di Venezia,Palazzo Ducale,Venice, Italy

Claude Bassier estorer,Sauvetage Archéologique,SOCRA, Quartier des Usines du Toulon24000 Perigueux, France

Luisa Bertacchi irector,Museo Archeologico Nazionale,Via Roma 1,Aquileia (Udine), Italy

Malika Boutira irection des Beaux Arts,119 rue Didouche Mourane,Algiers, Algeria

Gianfranco Bustacchini estorer,Accademia di Belle Arti,Ravenna, Italy

Paolo Cozzi estorer,

Opificio delle Pietre Dure,Via degli Alfani 78,50121 Florence, Italy

7



A n n e D e s tr o o p e r rc h a e o lo g ist , U n iv e rs ite C a th o liq u e d e L o u v a in , C /o A n na K ab an o p o ulo u ,V o u lg a ro k to n o u - F ra n z i, 1 4 ,A th e n s 7 0 8 , G re e c e

Ed ith D ie tz e n thr o p ol o g y C o ns e rva tio n L a b o ra to ry , N H B R o o m 3 61 , S m ith s on ia n I ns tit u tio n ,W a sh in gt on , D .C . 2 0 56 0, U. S. A.

M o ng i E n na ife r u ra to r, M u s ee d u B a rd o, a n d D ire c to r , C o rp u s d e s M o s a iq u e s d e T u n is ie , M u s e e d u B a rd o , Le B ar d o , T u n is ia

J e ro n im o E s c a le ra U re n a es to rer ,C h ie f o f th e M o s a ic s D e p a r tm e n t, Ist itu to de C o n s e rv a c io n y R e st au ra cio n d e O b r a s d e A r t e,

P ala c io de A m e rica ,A ve n ida R ey e s C a tol ico s , M ad rid 3 , S p ain

An dre a s F ar m ak as e sto re r,D e p a r tm e n t o f A n tiq u it ie s ,N ic o s ia , C y p ru s

E liz a b e th F ig ue ire d o C a br al e st or er, M us eu N ac io n a l d e Arq u eo lo g ia e E th n o log ia ,R u a S o u s a P in to n . 1 2 , 1 D to ,M o nt e A b ra a o ,O u e lu z, P o rt u g a l

P ie ro F riz z i e st ore r, O p ific io d el le P ie tr e Du re ,V ia de g li A lf a n i 7 8 , 50 12 1 Fl o re n c e , It al y

F ra n c is c o G a g o B la n c o e s to re r,M u s e o A rq u e o log ic o N a ci o n al V ina ro z 36 , 1 D ,M a d rid 2 , S p a in

M ic h al Ga m zo u a m ar g a ni t S tre e t, 2 2 , R am a t-G a n, Is rae l

An dr e a s G e or g ia d e s hi ef Co n se rv ato r, N u m is m a tic C o lle c tio n ,

N a tion a l A rc h a e o lo g ic a l M u s e u m ,To s its a 1 ,Ath en s 14 7, G re ec e

M o ha m m e d G ho uj

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B o g d a n K o v ac ev ic

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Co ns e rva te ur C h a rg é d u Se rv ice d e R e st a u ra tio n d e s M u s e e s C la s s e s e t C on tr o le s , P a la is d u L o uv re ,Pa ris , F ra n c e 75 0 4 1

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8



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irecto r,C han ti er d A d M e rcur i (Mo ro cco ) ,E c ole F ranpa ise,Pa lazzo F arne se,Pia z za F a rnes e ,001 8 6 Ro m e, I ta ly

Maur ice Le noir c ole F ranp a ise,Pa la zzo F arne s e,Pia z za F a rnese ,0018 6 Ro m e, I ta ly

La w ren ce Ma jews ki ro fess o r,Co ns erv at ion Ce nte rof T he In stit u te o f Fine Arts , New Yor k Un iv ersi ty ,1 Eas t 78t h Str e et,Ne w Yo r k, Ne w Yo r k 10 0 21, U .S.A .

F abri z io M ancin elli ura tor,De pa rtm e nt o f Me die va l a nd M ode r n A rt, D ire c tion G en er al o f t he V atic an M us eu ms ,V a tica n City

G iuse ppe M arine lli IB A -Ge ig y S. p .A.,C ase lla Po stale 88,2 1 047 S aro n no (V a.), I ta ly

J agod a Me d er rt Histo rian, Cura t or of Mon u men ts,Re pu blic ki Za vo d z a Zas tit u S po me n ika Ku ltur e, 410 00 Za g reb, L ivad iceva 1,Y u gos la via

Joh an an M intz ke r ir e ctor, S ub -De pa rtm en t o f C on se rva tio n, Dep a rtm e nt of Anti q uitie s ,P .O. B o x 58 6 ,J erusa lem, Israe l

Lau ra Sb or do ni M o ra h ief R estor e r,Pao lo Mo ra s ti tuto C en tr ale de l R es tau ro ,

P iaz za Sa n Fra nc es co di Pa ola 9 ,0 018 6 Rom e, It a ly

M a ra N im mo e storer ,Istit u to, C entra le de l Res t auro , P iaz za Sa n Fra nc es co di Pa ola 9, 0 018 6 Rom e , Ita ly

Wil liam E dwa rd No vis ri vate C ons u ltan t, Ba tc helo rs,Barr s Gre enH o rsha m , En g land RH 1 3 70 1 3

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Giro Picc io li o prin tend en za A rche o logic a ,P iaz za Mu se o 18 ,Nap les, I t aly



P et e r P op o v r tis t- P a in te r , D e p a rtm e n t o f C o ns e rv a tio n a n d R e s to ra tio n o f C u ltu ra l P ro p e rt y , N at io na l In st itu te f o r H is to ri c a l M o n u m e n ts ,4 4 , b o u le v a rd D o n d o u ko v , S o fia , B u lg a ria

C iro R o b o tti rc h ite c t,U ni ve rs ity of N a p le s ,V ia A . D ia z 7 ,8 0 0 5 5 P o rtic i (N a p o li), Ita ly

H . R o os e ns ire c to r, S e rv ic e N a tio n a l d e s F o u ille s , M in is te re d e ('E d u c a tio n N a tio n a le e t d e la C u lt u r e ,P a rc d u C in q u a n te n a ire 1 ,B - 1 0 4 0 B ru s s e ls , B e lg iu m

Am y R o se n be rg s s is ta n t C u ra to r in C o n s e rv a tio n , K e ls e y M u s e u m ,T h e U n iv e rs ity o f M ic h ig a n , 43 4 S ou th S ta te S tre et ,A n n A rb or , M ich ig a n 4 8 1 0 4 , U .S .A .

R a ffa e lla R o ss i M an a re si c ie nt ifi c O ffi ce r, C en tr o p e r la C o ns e rv az io n e d e lle S c u ltu re a ll'A p e r to , V ia d e ' P ig n a tta ni 1 , 4 0 1 2 4 B ol o g n a , Ita ly

A b d a lla h S ai l ire c tio n d es B e a u x A rts, 1 1 9 ru e D id o u c h e M o u ra n e , A lg ie rs , A lg e ria

R o m a n o S e re n a o p rin te n d e n za B e n i A m b ie n ta li e d A rc h ite tt on ic i d i V en e zi a, P a la z z o D u c a le ,V en ic e , I ta ly

M a rc e l S te fa n ag g i h ie f o f L a bo ra to ry , La b o ra to ire d e R e c h e rc h e d e s M o n u m e n ts H is to riq u e s ,7 7 4 2 0 C h â te a u d e C h a m p s -s u r-M a rn e , F ra n c e

G io v a n n i U rb a n i ir ec to r, Is titu to C e n tr a le d e l R e s ta u ro , P ia z z a S a n F ra n c e s c o d i P a o la 9 , 0 0 1 8 6 R om e , Ita ly

M ar ia L ui s a V e lo c c ia u p e rin te n de n t,S o p rin te n d e n z a a lle A n tic h ita de l La z io , P iaz za d e lle F in an z e 1 , 0 0 18 5 R o m e , Ita ly

R o sa lia V a ro li r t H is to r ia n , Ist itu to C e n tra le d e l R e s ta u ro, P ia zz a S an F ra n ce sc o d i P a ol a 9 ,0 0 1 8 6 R o m e , I ta ly

C a th e rin e V er no o j a b rie l M e ts u s tra a t 1 6 , A m s te rd a m , H o lla n d

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5 0 12 1 F lo re n c e, It al y

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Alb e rto V illa IBA -G eigy S .p.A., Case lla Pos ta le 88 ,2104 7 Saro n no (Va.) , Italy

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R o lf Wih r esto rer ,B aye r. Land esamt für Den kmalp flegeAus s enste lle B am ber g -. Sch los s See h of,860 2 Mem melsd o rf b. B a mber g ,Fe de ral R e publ ic of G erm an y

M. Y a nkelo v ich. rch a eolog ist,Via Maria Cristi na 2,001 96 Ro m e, Ita ly

1 CCRO M Staff

Par tic ipan ts ' r ganiz at ion

B e rnard Feilde n P aul Sch wa rtzb aum Gio rgio To rraca

Patri cia Bon ic attiG aö l de G uich en Pia Pierre Vi ckii Ric har dso nC ynth ia Roc kw ell



G L O S S A R Y

A rr icc io - T h e p re lim ina r y pl as te r la ye r s pr e a d o n m a -so n ry w a lls . It is le ft ro u g h s o t h a t th e fin a l t o p la y e r, in to n a c o , w ill a d h e re m o r e e a s il y . A ls o k n o w n a s s c ra tc h c o a t.

B e m a - A r a is e d s ta g e fo r th e c le rg y i n th e a p s e o f E a rly C h rist ia n c h u rc h e s .

B uo n fr e s c o - Th e d e c o ra tion o f w al ls a nd c e iling s w ith p ig m e n ts m ix e d w ith w a te r a n d p a in te d up o n n e w ly -a p p lie d , m o is t lim e p la s te r , a s d is t in c t f r o m p a in t in g a se c c o o n d r ie d p la s te r s la k e d d o w n w it h w a t e r . In th is m et ho d , th e c o lo ur s pe n e tra te t he p la s te r a n d

th elim e s e rv e s a s a b in d e r. C o n s e r v a t io n - A n y a c ti o n w h ic h d ir e c tl y o r in d ir e c tl y

p ro te c ts a w o rk b y im p e d in g th e c a u s e s o f d e te rio ra -tio n o r p re ve n ts c on tin u e d lo ss e s .

C ru s t a e - In la id w o r k o n w a lls o r f lo o r s . C u b e - W o rd u s e d i n s te a d of te s se ra . D e ta c hm e n t - T h e op e ra tio n o f d e ta c h in g , w ith m e ch a ni -

c a l m e a n s , t h e la ye r o f t e s s e ra e fr o m it s s u p p o r te it he r a t t he le ve l of th e r ud u s o r a t th e le v el o f t he n u c le u s .

F o u n d a t io n - T h e f ir s t, u n d e r ly in g , h id d e n le v e ls o f a m o s ai c , fo rm e d b y th e ru d u s a n d th e n u c le us .

G io r n a t o - A n a r e a o f w o r k t h a t c a n b e c o m p le t e d in on e d ay .

H y p o c a u s t- T h e u n d er g r o un d c h a m b e r o r d u c t s o f th e R o m a n s y s te m o f c e n tra l h e a tin g b y . m e a n s o f w a rm a ir flu e s .

Int o n a c o - T h e f in a l, s m o o th p la s te r la y e r f o r f r e sc o p a in tin g . M a d e from lim e a n d s a n d a n d la id o n in s ec -tio n s a c co rd in g t o th e a m o u nt o f w o rk t he a rtis t p la n sto e xe c u te e a c h d a y .

L a cu n a e - G a p s in a m o s ai c ca u s e d b y m is s in g pa r ts .T h e y m a y co m p ris e th e L os s o f t e s s e ra e a n d th e se tt -in g b e d o r, in a d d iti o n t o th e s e , th e l o s s o f p a rt o fth e fo u n d a tio n to o .

L ift in g - T h e o p e ra t io n w h ic h c o n s is t s o f d e ta c h in g a m o s a ic a n d t ra n s p o rtin g it to a w o rk r oo m . T h is m igh to r m ig h t n o t b e fo ll o w e d b y p la c in g t h e m o s a ic o n a n e w s u p p o rt.

M or ta r- A n a rti fic ia l a g g lo m er a te o f g ra in s o f s a n d he ld t o g e th e r by a bi nd e r lim e , c e m e n t , or r es in ) a nd u s e d to h o ld s to n e s o r b r ic k s to g e t h e r o r t o m a k e a l a y e r o v e r s o m e o th e r s u rf a c e .

N u c le u s - Th a t la ye r of t he m o s a ic fo u nd a tio n d ir ec tl ybe lo w t h e s e ttin g b e d a n d a b o v e th e ru d u s . I t c o n s is ts o f a f in e m o rt a r o f lim e , s a n d , c r u s h e d b ri c k s o rc e ra m ics a n d st on e s w ho s e m a x im u m d im e n s io n is 2 c m . I t c a n b e a p p lie d in s e v e ra l c o a ts .

O p u s s e c tile - R o m a n m o s a ic m a d e w ith l a rg e te s s e ra e s e t i n g e o m e tr ic a l p a tte rn s .

O p u s s ig n in u m - A c o m p o u n d o f b ro ke n p ie c e s o f te r ra c o tta p o u nd e d to g et he r a nd m ixe d w it h lim e. U s ed a s a p r o t e c t io n a g a in s t h u m id it y , i t s n a m e d e r iv e s fro m t h e R o m a n to w n o f S ign ia ( no w S e g n i) in L a tiu m .

P o z z o la n a - V o lca n ic a sh u s ed fo r m o r ta r o r h yd r a u li c c e m e n t.

R e s to ra tio n -T h e u s e o f a v a r ie ty o f te c h n iq u e s to re tu rn

a w o r k o f a r t t o t h e c lo s e s t p o s s ib le s e m b la n c e o f it s or ig in al c on d it io n.

R u d u s - A c r u de r la y e r o f t h e m os a ic fo u n d a ti o n , ly in gb el ow th e n u c le u s, a n d us u a lly m a d e u p o f m o rt a r o f l im e , s a n d , c ru s h e d c e r a m ic s a n d s to n e s w h ic h m a y b e a s b ig a s 1 0 c m . In fl o o r m o s a ic s , i t c o m es b e tw e en t h e n u c le u s • an d t h e s ta tu m e n; in w a ll m o -s a ics , b e tw e e n th e w a ll i ts e lf a n d th e n u c le u s .

S e a m - .A c u t w h ic h h a s b e e n r e fille d w ith te s s er a e w h e n t h e di ffe r e n t pa r t s o f a d e ta c h e d m o sa ic h a v e b e e n

p u t t og e th e r a g ai n o n . a ne w s up p or t. S e ttin g b a th - S e e s e tt in g b e d . S e tt in g b e d - S itu a te d b e tw e e n th e n u c le u s a n d t h e t e s -

s e ra e , th is is u s u a lly in v is ib le i n th e fin is h e d m o s a ic . U s u a lly m a d e o f l im e a nd m a r bl e po w d e r , te ss e ra e a r e s e t in t o it w h e n it is fr e s h a n d , c o n s e q u e n ti ly . a re h e ld in p la c e w h e n it h a rd e n s.

S in o p ia - A la rg e d ra w in g m a d e o n a w a ll in p re p a ra tio n fo r s e tt in g a m o s a ic o r p a in t in g a m u ra l. It s e rv e s a s a g u id e t o th e a r tis t fo r th e g e n er a l l in e s of t he c o m p o s it io n . I t i s d r a w n o n th e a rr ic c io , g e n e ra lly in b la c k o r b ro w n c o lo u rs . A ls o k n o w n a s a c a rto o n .

S m a lt - O p a q u e c o lo u re d g la s s m e lte d i n a fu rn a c e a n d th e n b ro ke n u p in to te s s e ra e .

S t at u m en - T h e d e e p es t, p ri m ar y la ye r o f t h e fo un d a -

ti o n o f a fl oo r m o s a ic, ly in g b e tw e e n th e s oi l a n d th e r ud u s. I t is f or m e d o f a b e d o f st o n e b lo ck s w h ich c a n b e a s la rg e a s 4 0 c m in d ia m e te r . I n a w a ll m o s a ic ,th e w a ll ta k e s t h e p la c e o f th e s ta tu m e n .

S to n e - A n o th e r w o rd fo r t e s s e ra . S tr ap p o - T h e p ro c e s s o f l ift in g a m os a ic b y cu tt in g th e

te s s e r a e l o o s e fr o m th e ir s u p p o r t . T h is is u s u a lly p r e c e d e d b y b in d in g t h e s u r fa c e o f th e m o s a ic t o a fi rm , te m p o r a r y s up p o rt w it h a s tr o n g b u t re -m o va b le a d h e s iv e .

S u p p o rt , n e w - A s u p p or t e s p ec ia lly m ad e t o h o ld m o -s a ic s w h e n th e y h a v e b e e n r e m o v e d fro m th e ir o rig -in a l p o s it io n . I t c a n b e m a d e o f w o o d , o f lim e m o r ta r . of c em e n t, o f r e in fo rc e d c o n c re te , o f sy n th et ic re s in s , e tc .

S up p o rt, o ld - T h e st at um e n a n d th e s oi l f or f lo or m o -s a ic s . F o r w a ll m o s a ic s , th e o rig in a l w a ll it s e lf.

Te r ra zz o - A f lo o r c om p o s ed o f c h ip s o f m a r b le s et in w h ite o r co lo u re d c em e n t.

T e ss e lla - A n o th e r te rm fo r th e m u c h m o re w id e ly u s e d a n d kn o w n w o rd te ss e ra . B o th w o rd s re fe r to e x -a ct ly th e s a m e th in g . S e e te s s e ra .

T e s se ll at um - Al l o f th e te s se ra e , pl ac e d si de b y s id e ,fo rm in g t he v is ib le p a rt o f a m o s ai c.

Te s s e r a - A p ie c e of s to n e , o f c e r a m ic , o r o f g la s s ,u s u a lly c o m p o s e d o f f o u r p a r a lle l si d e s , us e d in m a ki n g m o s a ic s . T h e si ze c a n ra ng e f ro m a fe w m illi-m e tr e s t o 3 to 4 c m .

T r a t te g g io - A s e r ie s o f p a r a lle l l in e s , in d ra w in g s o r p ai n tin g s , u s e d to in d ic a te g e n er a l f o rm s . A ls o c a lle d h a tc h in g .

T re a tm e n t - A c tio n t a k e n to p re s er v e s o m e th in g o r t o re s to re i t.

V e rd e a n tic o - G ree n p o rp h y ry .

1 2



OFFICIAL PAPERS



T H E C ON SE R VA TI ON O F PA VE M EN T MO S A IC S BE F O R E MO D ER N TIM E S: A SE LE C TIO N F RO M TH E M OS A IC S O F G AU L

b y He nr i L av ag ne

Tr an sla te d fro m the F re nc hby P atr ici a B on ic att i

A t t h e op e n in g o f thi s s y m po si u m , o rg an iz e d to e x a m in e p re s e n t-d a y p ro b le m s c on ce rn in g t he c on se rv at ion o f m o sa ic s i n t he b ro ad es ts e n s e o f th e w o rd , it se e m s a p p rop ria te to p re -s en t a b a la n c e sh ee t o f o u r p re d e c e s s o rs ' m e -th o d s . T h e p u rp o s e o f t h is e v a lua tio n is n e ith e r to d e p lor e th e ir e r ro rs no r t o pa y ho m ag e toth e ir e x p e r ti s e b u t to b e t t e r u n d e rs t a n d t h e w a y s in w h ic h t h e y a p p roa c h e d t h e s a m e d if-fic ul t ie s w h ich w e en co un te r t od ay , h op in g t olea rn fr o m t h e ir e x p e r ie nc e. O n t he t e c h n ica lle v e l, a s e r ie s o f e m p iri c a l p ro ce d u re s ha s b ee n in us e sin ce th e en d of th e 1 8t h c e n tu ry .T h e y w e re p e r fe c te d in s e v e ra l s ta g e s d u r in g th e co ur s e of th e 1 9 th c e n tu ry . O n th e a dm in is -tr a tiv e l e v e l, v a rio u s , f o rm u la e h a v e b e e n tr ie d , s u c h a s s ta t e sc ho o ls , p r iva te e n t e rp ri s e as -s o c ia te d w ith m us e u m s , w h ic h h a v e a llo w e d th e u s e , w ith v ar y in g su cc es s, of te ch ni c a l d isc o-v e ri e s . W e a re c o n c e r n e d w ith t h is e v o lu t io n p rim a rily in F ran ce b ec au se it is th e a re a m o s t fa m ilia r to m e , a nd a lso b ec au se it w as th er et ha t I ta lia n a rt ist s e m igr at e d a n d fo un d a p a r -t ic u la r ly fe r t il e f ie ld f o r t h e ir d is c o ve ri e s .

S c h e m a tic a lly , w e c a n d is tin g ui s h fo u r p e -rio d s i n t h e h is to ry o f m o s a ic c o n s e rv a tio n .

T h e fir s t p e rio d , wh ich l a s ts fro m the R en ai s -s a n c e t o t h e e n d o f t h e 1 8 th c e n tu ry, is t h e l e a s t

w e ll k no w n ( 1) . D et a c h m e n t a n d res to rat io n o fm os ai c s m us t h av e b e en ra re ly pr ac tis ed a n d e x a m p le s fro m th e p e r io d a re fe w . In fa tu at e d w ith an tiq uit y , R e na iss an ce m an e n c o u n te re d forth e fir st tim e th e pr ob le m of re m o v ing p av e-m en ts . T he e ar lie s t k n ow n ex am p le in Fr a n ce a p p ar e n tly is th e d e tac hm e n t o f a m o s a ic fr o m S ain t- Gi lle s ( G a rd ), ex e cu ted i n 1 5 44 a t th e r e q ue st o f F ra n c is I i n o rd er to d ec or at e h is p al a c e a t F o n ta in e b le a u (2 ) . W e k n o w o f o th e r e x am p les d u rin g th e c ou rs e o f t h e 1 7 th a n d 1 8 th ce nt ur ies , b u t a lw a y s d e a li n g w ith sm a ll fra g -

m e n ts , g e n e r a ll y f ig u r a t iv e m e d a ll io n s w h ic h w e re t a k e n o u t o f a g e o m e tr ic b a ck g ro u n d a n d p la c e d in fr a m e s a s p ic tu re s . T h e p o in t o f v ie w

w h ic h i n s pi r ed t h e s e s am p lin gs is n o t v er ydif fer en t f rom t ha t w hi ch pr od uc ed th e e m b le m a u s e d in a n tiq u ity .

N o tec hn ic a l p ro c e d u re fr o m t h is fi rst pe rio d of th e h is to ry o f mo sa ic co n s e rva tio n is kn ow nto u s .

T h e s ec on d p e rio d ( 1 8 0 0 -18 30 ), mi g h t b e c al l-e d t h e B e llo ni - A r ta u d P e r io d a f te r t h e tw o gr ea t p io n e e rs a nd d o m in a n t fi g u re s i n t h e fie ld a t t h a t tim e. D u rin g th e s e thi rty ye ar s , th e n ee dto pr e s e rv e pa ve me n ts in t he ir e n tire ty , w he th e rfi g u ra ti v e o r g e o m e tr ic, b e c a m e o b vi o u s a n d t w o m e t ho ds o f d et ac hm e nt w e re d ie v o lop ed c on cu rre nt ly. Th e fir s t w a s t ha t o f P . S c hn eid er ,a p ro fe ss or o f d ra wi ng fr om V ie nn e, (I se re ),w h o , im p re s s e d b y t h e a b u nd an ce o f m os ai c s in th e r e g io n , fo u n d e d a m u s e u m fo r m o s a ic s (3 ).

- H is pr o c e d u re w as s im p le a nd v e ry h a z a rd o u s : it c o n s is te d o f e x c a v a tin g b e n e a th th e s e ttin g be d an d rep la cin g the e ar th wit h w o od en p rop s. W h e n t h e m o s a ic w a s e nt ire ly d e tac he d, h e s u r-r o u n d e d it w it h a fr am e tie d to cr os s b ra c ing su nd er the p av em e nt. O nly a th in lay er of pl as ter h e ld th e su rf a c e o f t he t e s se lla tu m to g e th e r . It w a s d e tac he d fro m th e g ro un d in its e nti re tya n d r e la id in a sp e c ia lly -d e s ign ed e xc av at ion .

It is h a rd ly ne ce ss ar y t o p o int ou t t h e di ffic ul tie s o f t h is p roc e s s wh ic h, be si d e s , pe rm itt e d o n ly th e p re s e rv at ion o f s m a ll a re a s o f m o s a ics .

It w a s F . B e ll o n i, a n I ta lia n , w h o a c h ie v e d de ci siv e pro g res s. H e w e nt to Pa ri s i n 1 80 0 to

n a t u r a li z e m o s a ic s a t th e r e q u e s t o f t h e F re n c h a m b a s s a d o r to R o m e , a n d re m a in e d i n F ra n c e fo r tw e n ty -e ig h t y e a rs a s a g o v e rn m e n t em p loy ee u n d er th e E m pir e a n d l a te r u nd e r th eR e st o r a ti o n . I t is im p o r t an t t o k n o w a bo ut th ed e v e lop m en t o f B e llo n i's P a r is ca re er in or de rto un de rs tan d ho w he w as a ble to a cc om p lis hh is w o rk , t h a n k s to a sc h o o l w h ic h i n a s e n s e for es ha do w s o ur re st or a tion in sti tut es . F irs t, am os aic w or ks ho p w as cr ea te d for hi m at th e

In s ti tut e f o r De a f M ut e s . In 1 80 2 it b e c a m e th eSc ho o l o f M o s a ics , u nd e r th e au sp ic es o f th e

15



e N

f d

< .4.wif ..46w etttw e ifiegw .,64.. c m66t .

Min istry of F ine A rts . In t h e c h ara c ter o f N a po-leo ni c g o ve rn me n t, th is sc ho o l w a s d e sti n ed to rival the Impe rial Man ufac tory of M osa ics in Fl or en ce a nd R om e . I n 1 8 07 , h is sp ac io us w or k-s h op a nd h is st ud en ts ' lo dg in gs w er e m ov ed t oth e ol d F r an c isc a n m o na s te ry a t 1 1 ru e d e

l'Ec ole d e M edic ine. W ith the retur n of the m on-a rch y in 1 815 , the Sc h ool o f M o sa ic s b e ca m eth e R oya l M os ai c Fa c tory un d er th e s pec ialpa tro na g e of th e Ki ng . In 18 2 6, w he n Be llon ihad to l e ave his old q uar ters, it w a s d u e to the fact o f b e lon g ing to t h e r o yal hou s eh o ld t h athe me ri ted h o us in g in th e r oy al m a rb le w are -h ou se o n th e C ha ill ot hi ll. Th es e d eta il s i llu s-tra te th a t in a s ta te s cho o l, h e ir t o Na p ole o nic c en tra lis m , a d ire ct re lia nc e on r oy al po w er s tillp rev ailed . It w as pre c isel y du ring this per iodth at t h e m ost rapid ly-c o mp leted and the grea t-est n um b er o f re s to ra tio n s w e re ca rri e d o u t in F ran c e.

Be lloni 's ac tivitie s w e re t w ofo ld: t h e m osa ic sc h ool ta ug h t h is st ud en ts a n art is tic tr ad e an dfulf ill ed o ffi ci al or de rs , n o ta bl y t he f lo ors for th e Lo uvre and the Tuil e ries , bu t it a lso p laye dthe role of a res torat ion i n stit u te ( 4 ). T han k s to a res earc h pr o jec t in h is wo rksh o p, h e p e rfec teda m e th od o f d eta ch m en t wh ic h w a s t he n alr ea dy k no w n in I taly and w hi ch so o n b e ca m e th e m e th-o d us e d b y al l m u se um s. T h e ad op tion o f th ism e tho d wa s ai d ed b y th e s u ppo r t of the m os t cel ebra ted s pec ialist in a ncie nt m osai cs o f the time , Fr a nco is A rtaud , Di recto r of the M use umof L yon , wh o be c am e its prom ote r. W e ha v e a

d esc ripti o n o f the me thod in h is bo ok, H is to ire a breg ee d e la p ein ture m os a ique : firs t, cle a nin g wit h a b rush , the n dry ing b y pa s sin g a w ire m esh cove red with glow ing hot c oals ove r the surf aceo f th e tes s ell at um ( 5) . N e xt , th e m os a ic is lu -br ic ate d w ith a c oat in g o f tur p ent in e m ixe d wit h w ax. The n th e pie c e i s div ided into pan e ls, th elin es f o r cu tting plac e d w her e the re ar e lac u na e ,fract ures , or a ne utra l ba ckgr ound . A row ofte sse ra e ar ou n d t he b or de rs of th es e pa n els i sne x t re m ov e d w ith a ch isel . Sla b s o f sla t e o r of th in m arbl e are cut to th e si z e o f the pan e ls.T h ese slab s ar e the n gl u ed to th e sur face of th etes sera e w ith a mixt ure o f w a x, t u rpe n tine and fine s and or o c hre , he a ted a lon g wi th th e sla b s.A fte r dry in g, th e pa ne ls a re sa w ed a pa rt wi th am ar ble c ut te r a nd d et ac he d pi ece by p iec e. be -g inn ing a t th e ed g es o f t h e m o sa ic . O n ce d e-tac h ed , t he s ett in g b e d is r em o ve d wi th a bu rin in ord er t o re a ch t he b ack sid e of t he c ube s.W ith th e s am e ma s tic a s b e for e , n ew s la bs o fm a rble are glu e d o n to t h e r e ver s e s id e o f th e fra gm e nt s, th us f orm ing a ty pe o f sa n dw ic h ,bo th s tu rdy a nd m o bi le. A fte r r ea ss em b lin g th ee le m en ts in th e ir n e w lo ca tio n, th e fro n t s la bs ar e d e tac h ed b y t re ati ng w ith h e at, w hil e tho s eo n th e re v ers e fo r m t h e n e w a nd p erm ane nts e ttin g be d . Th e jo in ts a re fi lle d lin w ith te s ser a ew h ich wer e re m ov ed a t th e tim e o f cu t ting . T h e m ast ic rem ain in g o n the sur fa ce is re m ov e d

wi t h a chis el F inal ly, p o lis h ing with pu m ice rest ores the pav eme nt t o its orig inal smo otha nd b rillia nt co ndit ion.

T his ing e nio u s p ro ce d ure wa s mu c h sa fe rth an p re vi ou s on es a s it m a in ta in ed a g rea te ra dh e re nc e to th e te x tur e o f the t es se lla tu m

an d em p loy e d re lativ e ly h o mo g ene o us m ate rials . In e x am in in g th is m et ho d , w e fi nd a c er ta in n umb er o f our own con tem pora ry te chnic al c on-c e rns . Th e pr o ced u re w as first a ppl ie d i n 18 1 9to t he la rg e mo s aic J eu x du C irq u e in Ly o n ( 6) .

Fig . 1 - J eux d u C ir que , (Lyo n ). D r awin g by A rtau d afte rt he re sto ra tion b y B el lon i

T he m osa ic (F ig. 1 ), p revio usly con s ide red i m -po ssib le to rem ove be c aus e of its g rea t siz e

(5 m. x 3 m .), w as deta che d an d re stor ed i nBe llon i's P a risi a n w ork s hop in l e ss t han one ye ar . It is als o wo r th no tin g th a t w h en B ell o niw e nt to L y on h e in vo lv ed the loc a l m a rb le w o rke rs in the p ro je ct, e xpl ai nin g to th em ea ch ph a se o f th e va rious ope ratio n s. T his p rov ided an imp o rtan t ad v ant a ge fo r su bse q uen t de tach -m ent s : Be llon i's in stru c tion s s u ffic e d w itho u treq uir in g h is a ct ua l p re se nc e th er e, 30 in 1 82 0 ,in th e c ase of a n oth e r m o sai c f ro m Ly on B e llo ni

was sati s fied to r e ceiv e th e fift y -eig ht se gme ntsin c rate s an d to wo r k o n th e m in hi s stu dio b e for e se n din g the m b a ck to Ly o n, th e a s se m -bla ge b eing don e by the m us e um itse lf (7) . Th e s yst e m t h us pe rm it ted a c on si de ra bl e s a vin g intime a nd m on e y.

F o r th e re st or at ion o f a n cie n t m o sa ic s, th ee x iste nce of a stat e fac tory for m os a ics w as agr e at a dva n tag e . It p rovi ded q ual ified craft sme n bec a us e on e of B ello r ti's w ork s ho ps w a s s ol ely de d ica te d to th e s m all c ub e m os ai cs , c al le da ncie nt m osai c s, in the Rom an s tyle . Th e sta tefa cto ry a ls o p ro vi de d sp a ce fo r sto r ing m a te -ri als, Bello ni h avin g am ong his resp onsi bilitie sth e s up er v isio n of th e ro ya l s to re ho us e of m ar -ble s us e d fo r off icial scul p ture com mis sion s or fo r inla yed mos a ics , cal led flore n tin es F inal ly ,the s tate fac tory prov ided

a pl ace for t e ach ingan d t ra ini n g st u den ts. T h ere wer e als o , ho w ev e r,v ery real d an g ers a t a t ime wh e n s tr ict r e sp e ct

6



F ig. 2 - C om ba t d e l 'Am o ur et P a n, (Ly on ) o rig ina l p an el

F ig . 3 - T he s a m e m o tif r e s to red b y B el lo n i

fo r t h e a u t h e n t ic ity o f a w o r k o f a rt w a s n o t ye t a bs o lut e. M ov in g co nt inu a lly fr o m t he p ro -d u c tio n o f m o d e rn m os ai cs to th e re sto ra tio n of a n c ie n t p a v e m e n ts , it w a s in ev it a b le th a t th e a rt ist s u c cu m be d to in c o r r e c t st y le s o r t e c h-n iq u e s. T h is is p ar t ic ul a r ly e v ide n t in d e tai ls o f

th e m o sa ic L 'A m ou r e t P a n , L y o n ( F ig s . 2 , 3 )in w h ic h B e llo n i's h a n d , e x c e lle n t in te c h n iq u e ,b e t ra y s it s e lf b y a s li g h t s ti f fn e s s w hi c h u n -q ue s tio na bl y e vo k e s th e Em p ire s tyl e.

T h e th ird p e r iod ( 1 8 30 -1 85 5 ) , w a s a tra ns i-tio n a l p ha se . A fter th e d e at h o f B e llo ni , f o llo w ed b y th a t o f A r ta u d i n 1 8 3 8 , th e m o s a ic fa c t o r y w a s c lo s e d a n d l o c a l m u s eu m s re a s s u m e d th ere sp o n s ibi lity fo r a ll th e w o rk o f m o s a ic de ta ch -m en t a n d c o ns er va tio n . N o t h av in g s p e c ia lis tsat th eir d isp os al , th e s e m us eu m s c al led u po n th e a rch ite c ts in ch ar ge o f t he c on se rv at ion o f c la s-si fie d w or ks o f a rt in th e D ep a rtm e nt o f H is -to ric M o n u m e n ts . B e llo n i's m e th o d w a s m o d ifie d a n d m a de m o re f le xi b le . W e h a v e a n e x a m p le o f t hi s in t h e d e s c r ip ti o n o f t h e d e t a c h m e n t o f a

m o sa ic fr o m V a iso n- la -R o m a ine , (V a u clu s e ), in 18 38 , e x ec ute d un de r the d ire ct ion o f P . R e na ux ,th e ar ch ite c t o f t he d e p a rte m e n t (8 ) . T h e s u r-

fa c e , 1 8 s q u a re m e tr e s , w a s d iv id e d in to th ir ty -fo u r p an e ls . S h ee ts o f c ar db o ar d we re t he nat ta ch ed w ith h e ate d b itu m e n , l e a vin g a se am fo r t he s a w c ut b e tw e en e ac h pa n e l. P lan k s o ffir wo od w e re glu e d t o e a c h of th e pa ne ls . A m ar -b le s aw w a s the n us e d t o c u t v er tic al ly ar o u nd t h e p a n e ls , fo ll o w in g t h e s e a m s . T h e t a s k o f d e ta c h m e n t b e n e a th t h e p a v e m e n t c a m e n e x t, th e ea rt h b e ing p ro g re s s iv el y r e p la c e d w ith b u n-dl es o f s tic ks . T h e de ta ch m en t o f th e t es se lla -tu m wa s ac co m pl ish ed b y ru ptu re , fol low in g th elin e o f cle a va ge s ep a rat in g t he r ud us fr om the n u cl e u s. E a c h p a n e l w a s the n lifte d o u t a n d it s b a c k in g r e d u c e d t o a t h ic k n e s s o f a p p ro x im a te ly 9 c en ti m e tr es t o w h ic h a c o at o f p la st e r w a s a p p lie d. A ll t he p a n e ls w er e t he n p lac ed o n ab ed o f s tr aw i n a w o od e n c ra te . T h e p la n w a s to re a s s e m b le t h e m o s a ic in th e M u s e e C a lv e t in A v ig no n , w h er e it wa s to r em a in , a n d to d e t a c h, b y a h e a t ing p ro c e s s, th e sh e e

t s o fca rd bo ar d glu e d t o it b y bi tum e n. U nfo rt un at ely ,th e lar ge s iz e of th e pa v e m e nt (6 m . x 3 m . )d id n o t a llo w it s im m e d ia te p la c e m e n t. T h e s h e e ts of b itu m ino u s c a rd b o a rd d rie d o ut , t h e p la s te r tu rn e d to d us t, an d th e c u be s be c a m e c o m p let el y d e ta c h e d fr om e a ch o th e r (F ig . 4 ). O n ly in th e l as t p e r io d o f th is hi s to ry o f m o sa ic c o ns e rva tio n w a s a n e w , s a fe r m e th o d p e rf e c t-ed b y a s ec on d g e ne ra tio n o f Ita lia ns e sta b lish e d in F ra n c e.

F ig . 4 - F ra g m e n t o f a m o s a ic fr o m V a is o n - la -R o m ai n e ,de ta c he d b y P. Re na u x

T he f ou rt h p e ri o d w a s t h a t o f th e M o r a s ,( 1 8 5 0- 19 1 3) , a n d w e o w e t o th is fa m ily , t wo g e n e ra tio n s o f w h ic h li v e d in F ra n c e , th e m a jo rp a rt o f th e m o sa ic re st or at ion s in th e so ut he rn p a r t o f G a u l. O r ig in a lly fro m U d in e , t h e M o ra b ro th e rs e sta b lis he d th ei r r es id en c e Fir st a t

17



F ig . 5 - F ra g m e n t o f a m o s a ic fro m Va iso n- la -R o m a ine ,o r ig in a l p a rt

Fi g . 6 - T h e s am e m o t if re s to re d by E . M o ra in 1 86 1

Ly o n, th e n at N im e s. T h ey w e re , l ik e Be lt on ',cr ea to rs o f m o d e rn m o s a ic s bu t th e y w or ke d st illm o re a s re s to re rs o f a n tiq u e p a ve m e n ts . In a n y ca s e , th ey c on s titu te d a fa m ily -ru n p riv at e e n te r-p ris e w ith n o tie s , o th e r t ha n c o n tr ac tu al , w iths ta te m u se um s . Th e ir m et ho d s di ffe re d fr om th o s e o f th e ir p re d e ce s s o rs in s e v e ra l r e s p e c ts : s tro n g p a pe r w a s a t ta c h e d to th e su rf a c e of th e te s s e lla tu m w ith a g lu e c o m p o s e d o f a m ix tu re o f g u m a ra b ic a n d rye f lo u r. S tr ip s o f c lo th w e re c a re fu lly s tr e tc h ed a c ro ss th is p a p e r a n d h e ld in pl a c e wi th th e sa m e g lu e . Th e c ut tin g op e ra -t io n w as id e nt ic al b ut th e b ac k su rf ac e o f t he m o s a ic w a s s c r a p e d d o w n to t h e n u c le u s . A rat he r th in be d of te s s e lla tu m w as t h u s o b ta in e d ,w h ic h w a s h e ld o n ly b y th e s h e ll- lik e la y e r g lu e d t o its s u r fa c e . T h e p r e p a r e d fra g m e n ts w e re t h e n s ea le d a fre s h in a c e m e nt w h ic h f or m e d t he f in a l la y in g be d . C lot h st rip s a llo w e d fa r

m o r e fle x ib ilit y in d et ac h m en t a n d a g re a te ra d h e r e n ce t o th e su rf ac e , b u t t he c h o ic e o f a p la n e o f cl ea va g e be tw e en t he te s se lla tu m a nd the n uc le us m a de t he p ro ce ss o f s e pa ra tio n v e ry d e lic a t e . B e si d e s th is , t he v e ry fr ag ili ty o f t he f r a g m e n ts re q ui r e d th a t t h e y re m a in in s m a ll s e ct ion s o f s ca rc e ly m o re tha n 6 0 s q ua re c e n ti-m e tr es . Th is m e an t th at th e re w e re n u m e ro u s joi n ts t o co v er a t t he t im e of re a ss e m bl y . D ue t o th e v irtu o si t y o f t h e M o ra s , h ow e v e r , t h e s e jo in ts w e re p er fe ct ly hi dd e n .

T he t wo g e ne ra tio n s of th es e a rti sts w o rk ed v e ry d iffe re n tly f ro m ea c h o th e r. T h e fi rs t d id n' t h e s ita te t o en tire ly re p lac e m is si n g f ra g m e

n ts, a n d t h e r e su lt is o f t e n b a f f lin g , d u e t o t h efi n e ss e o f t he e x e c u t io n a n d t h e b o ld n e s s o fth e in v e n tio n . W e h a v e a g o o d e x a m p le in a p a v e m e n t fro m V ai s o n -la -R o m a in e , ( V a u c lu s e ), d e tac h e d b y E . M o ra in 1 8 6 1 ( 9 ). A s th e m u s e u m o f Av ig n on w a s u n ab le to a c qu ir e e s e gm e nt o ft h e o r ig in a l m o s a ic , t h e a rt is t e nt ire ly r e c o n s -lru ct ed t h e m is s ing f ra g m e nt . C o m pa rin g it w ith th e a u the n tic p ie c e , w e a re s u rp ris e d to s e e t h a t a ll th e m o t if s w h ic h w e r e m is s in g h a ve b e e n e n tire ly in v e n te d ( F ig s . 5 , 6 ) . H o w e v er , w e c an b e tte r u nd e rs ta n d t h e li b e rt y tak e n b y th e a rtis t in r eg a rd to t he o ri g in a l w o rk o f a r t if w e re c a ll th a t t hi s p e rio d g re at ly fa v o u re d cr ea tiv e w o rk in m o s a ic s . In fa c t, u n d e r N a p o le o n I II, m o s a ic s c a m e b a c k u n to st y le w ith th e h e lp o f G a rn ie r , th e a rc h ite c t o f t h e P a r is o p e ra h o us e , w h o e n tru s te d a p a r t o f t h e g re a t h a ll to t h e V e n e tia n m o s a ic m as te rs S al via ti a n d F ac ch in a . F ac c h in a h im s e lf wa s in c ha rg e o f r e s to ring t he m o s aic fro m L ill e b o n n e, (S e in e- M a ritim e ), in 1 87 1 (1 0 ) .It is n ot s u r p ris in g , t h e r ef o r e , t o fin d i n t h ew o rk o f th e re st or er s of th is p er io d an e c ho o fth e r ic h c re a tiv ity the y w er e e x p re s s in g in th e ir o w n w o rk s a t th e s a m e tim e .

T h e w o r k o f t h e s e c o nd g e ne r a t io n o f th e M o ra

f am ily w a s l es s m a rk ed b y th e a rt is t ic tr en d s of th e ti m e. If w e c o n si de r th e m o s a ic fro m L u c -e n -D io is, (D i- tim e ), (F ig . 7 ), re s to re d b y C . M or a in 1 8 9 1 , w e n o tic e th a t a c e rta in o b je c -

ti v it y " i s b e g in n in g t o m a r k t h e r e s t o r e r ' s a p -p ro a ch ( 1 1 ). A ft e r th e d e a th o f C la u d iu s M o ra , ju s t b e fo r e t h e F ir s t W o r ld W a r , r e s to r a t io n s w e re i n c re a si n g ly l e f t t o th e in iti at iv e of th e p ro v inc ia l m u s eu m . Th e y be c a m e r a re ag a in , b e ca u s e o f t h e l a c k o f re al s p e ci a lis ts , an d th e y w e re c h a ra ct e rize d b y t h e r e g ul a r u s e o f c em e n t a n d a n im a l g lu e .

T h e s o le p u rp o s e o f t h is r e p o r t h a s b e e n t o g iv e a br ie f s u m m a ry o f th e ev o lu tio n of te c h-n iq u e s in th e re s to ra tio n o f p a v em e n t m o s a ic s , a n d to p la c e t h e m in t h e ir h ist o r ic c o n te x t. I t i s e v id e n t th a t t h e m o st fa v o u ra b le pe r iod s h a v eb e e n t ho s e w h ic h c o m b in e d a ta s te f o r a rch a e o -lo gy a n d a de s ire t o s a ve a n a rt ist ic h er ita g e(a s u n d e r t h e F ir s t E m pi r e ) w it h , o n th e o t h e r h a n d , a n a rt is t ic m o v e m e n t w h ic h le d t o th e c re a tio n of m o de rn w o rk s. W h et he r w ith in th e g o v e rn m e n ta l fra m ew o rk o f B e llo n i's fa c to ry or th a t o f pr iv a te e n te rp ris e u n d er th e M o ra s, cr e-a tion a nd r es to ra tio n we re n e ve r s e pa ra te d. T h is c o e x is te n c e in t h e s am e w o rk s h o p o f a te c h -n iq u e d e d ic a te d t o t w o t o t a lly d if fe r e n t a im s c a u s e d i n e v ita b le e r ro rs . A s e c o n d p o in t to re -

18



F ig . 7 - F r a g m e n t o f a m o s a ic f r o m L uc -e n -D io is, re s to r e d b y C l. M o ra in 18 91 a n d by C l. B as si e r in 1 97 2

m e m b e r is th e n e c e s s ity o f t ra n s m itt in g k n o w -le dg e . W h e n th e m a s te rs o f a s c h o ol d is a p p e a r-e d w ith o u t h a v in g tra in e d d is c ip le s , a p h as e of s ta gn a tio n en s ue d . I t is c le ar th a t t he m o s t fr u it fu l p e r io d w a s t h a t o f s t r ic t c o ll a b o ra ti o n

b e tw e e n the te c h n ici a n , B e llo n i, an d th e s c h o la r,A rt a u d . I t is t o th e m t h a t w e o w e t h e b irt h o f o u r sc ie n c e.

T h e di s c u s si o n w h ich f o ll o w e d t h is lec tu re w ill be fo u nd o n p a ge 3 7.

N ot e s

1 . O f t h e pe rio d b ef o re th e R e n a iss a n c e we k n o w v e ry li t tle . O n ly a fe w d e t a il s h av e c o m e d o w n to us o f t h e m e th o d s u s e d i n t h e 8 t h c e n t u ry w h e n th e P o p e au tho riz ed C h ar lem a g n e t o d eta ch p a ve m e n t sa n d w a ll m o s a ic s in R o m e a n d R a v e n n a . S e e P . V e r zo ne , " L a d e m ol iz io ne d e i p a laz zi i m p e r ia li d iR o m a e d i R a ve n n a n e l q u a d ro d e lle n u o v e • f o rz e p o litic h e de l s e c . V III in Fe st s ch rif t F r . G er ke B ade n-B ad en , 1 96 2 , p p . 77 -8 0 .

2. J . P o ld o d A lb en as , D is c o u r s h is to r ia l d e ( a n t iq u e e t il lu s t re c it e d e N im e s , L yo n, 15 6 0 , p . 5 9 .

3. J . D e lorm e , P . S c h ne ide r Vie nn e, 18 47. IP . S chn eid er ,H is to ire d e s a n t iq u it e s d e la vil le d e V ie nn e, V ien n e , 18 80 . S ch n e ide r w a s a c ti v e a t V ie nn e fro m 1 7 5 6 to 1 8 1 6 . H is b o o k w a s p u b lis h e d a fte r h is d e

a t h. 4. F or m ore d eta ils , s ee th e u np ub lis he d arc hi ve s in

t he A r c h iv e s N a tio n a le s , P a ri s , se rie s 0 2 , 0 3 .

5. F . A r ta u d , H ist o ir e a br e g e e de la p e in tu r e e n m o -

sa iqu e, su iv e d e la d e s cr ipt ion d es m os aiq ue s d eL y o n .. . a in s i q u e d u n a p e rc u r e la tif a u d e pl a c e m e n t d e c e s p a v e s , Ly o n , 1 83 5 .

6 . F or m or e o n t his p av em en t, se e H . S te rn , re cu eilg e n e r a l d e s m o sa iq u e s d e la G a u le L y o n n a is e , I I, 1 , n o. 73 .

7 . Ib id . II, 1, no . 1 .

8 . O n th is m o s a ic , se e H . L a v a g n e , " T ro is m o s a iq u e s in e d its d e V ai s on - la -R o m a in e , in R ev ue ar c h e ol o gi q u e d e la N a rb o n n a is e , X , 1 9 77 , p p. 18 3-1 88 .

9 . G . La fa y e, ln v e n ta ire s d e s m os a iq u e s d e la G a u le , P a ris , 1 90 9, I, n os . 1 21 an d 12 3 .

10 . A . B la n c he t, ib id. I I, n o . 1 0 5 1 . J. P . D a r m o n , La mo sa iqu e d e Lil leb on n e 1 9 7 6 , a n d L a m o s a iq u e d e

L ille b o n n e au jo u rd 'h u i , i n A c te s d u c o llo q u e C o c h e t .R o u en , 1 97 5.

11 . G. La fa y e, ln v e n ta ire n o . 1 3 7 .

9



T HE W AL L M O S A IC: HI S T O R Y O F R E S TO R A T IO N , E VO LU TIO N O F TE CH NI Q U E S

T h e h ist ory o f th e r es tor ati o n of wa ll m o -s aic s, of i ts m e tho ds an d p roc es ses , is in ma ny c a s e s id e n t ic a l w it h t h e h is t o ry of t h e m o nu -m en ts w hic h the mo sa ics we re int e nd ed to de c-or ate . T he art of m o sa ics , c os tly as a r esu lt o fth e m a ter ia ls us ed an d th e hig hl y s k ille d w o rk-m a ns hip re qu ired , i s a n ` a rt o f trad itio n a nd p a -tro na ge . It ca nn ot b e im p ro vis ed , e ith e r in i t ste c h n iq u e s o r in its a r tis t ic q u a li ty . T h e l a tt e ris la r g e ly c o n d it io n e d b y th e vi rt u o s ity o f th e ar tisa ns ch ar ged w ith re n de rin g i ma ge s, t he o-re tic a lly ma de to las t b y m ea ns of c ol o ur ed gla ssan d f in e ly c ut s to n e . T h e f am o u s d ef in it io n th a tG hirl an dai o g av e t o m os aic s, "th e tr ue pi c tu refo r e te rn ity ", w as of ten ci ted lat e r for i ts i ne xa c -

titu de . B ec au s e the a r t w ith wh ich w e a re c o n ce rn -e d p re s up po s e s s u b s ta n tia l m ea n s , it w a s c o n -s e q u e n tly in all pe r io d s c o n si d er e d a n ide al e x -p re s si o n e ith er of po we r o r o f h igh sp irit u a lity , d e p en din g o n the ca s e, or ev e n o f b ot h a t o n ce .

In t h e M e dite rra ne a n ba s in du ring th e R om an p e riod ri c h p riv at e in di v id u al s u s e d m os a ic s t o de co r at e c ert a in p a rts o f th eir ho us es . L a te r ,th e B yz ant ine st ate ut iliz ed mo sa ics pr ofu se lyt o i llu s t ra t e , in a d u r a b le f a s h io n , C h r is t ia n do gm a in t he de co rat ion of the c h ur ch e s, an dth e s p le n do u r o f th e E m pe ro r, C h ris t's re p re s e n -ta tiv e o n e a rt h , in h is d w e llin gs . M o s a ic s s e rv e d th e P op es for co mp ara ble p u rp ose s. La stly , th ep o w ers fi g h t ing fo r p ol it ic a l s up re m a cy , a n d d e s iro u s o f c o m pa r in g t h e m s e lv e s w ith , im ita t-in g, o r s u p p la n ting B y za n tiu m , d id th e ir u tm o s tto p ro m o te l av ish d e co ra tio n s . T h e se , c h a rg e d w ith p o lit ica l a n d re ligi o us s ign ific a n c e, w e re c re a te d a d h o c in m o s ai c s, mo st o fte n b y B yz an -t ine a r tis t s. I t w as th us th a t t he A r ab ca lip h s , C h a rle m a g n e , th e O rt h od o x pr in c e s o f K ie v ia n R u ss ia, th e p atr on s o f M ou nt At h os , t hos e ofM on te C a s si no , th e d og es of Ve nic e a nd th eN o rm a n k ing s o f S ic ily , to m en tio n o nly th em os t fa mo us , co ntr ibu ted to th e d iffu sio n o f th is

a rt, w h ich ha d b ec om e a t ru e st a tu s s y m b o l of th e Mi d d le A ge s .Of tho se mo nu me nts tha t h ave b een pr ese rv -

e d to o ur da y ( a s ma ll p art of the w hol e), ma ny ,

by Iri n a An d re es c u

T ran sla ted fro m the F ren c hb y E lisa be th S c h wa rtz ba um

al m o s t a ll o f t he m ch u r c he s, h a v e k e p t t he irfun cti on an d t h er efo re the n e ed fo r t h ei r d e co -ra tio n . H ow ev er , th e c h u rch e s a lr e a d y o ov er e dw ith m o sa ic s in th e M id dle A g e s w ere k e pt in a go od sta te of rep air du rin g t he co urs e o f t h ece n tu rie s b y a rti s an s w h o se ar tis tic c on c e p tio nw a s g r e at ly d iff e re n t f ro m , if n o t o p po s e d to ,th a t o f t he fir s t m o s a icis ts; th is i s t h e c a s e o fth e m o nu m e nts in Ita ly, fro m the R e na iss an ce o n. C h ur c h e s in th e B y za nt in e E m p ire we re tr an s fo rm ed du rin g t h e co u rs e o f t h e ir h isto ry in to mo sq ue s , a nd th e m o sa ics re p re se n ti n gC h ri st ia n im a ge s w er e d e s tr o ye d or h id d e n f ro m v iew .

H av ing ce as ed to live a c tiv ely w ithi n it s t ra-d it ion a l f orm u lae , th e a rt of m o sa ics so on be -c a m e a rar e c raf t an d o nl y s u rv ive d t o o ur da y thr o ug h r es tora tio n w or ksh op s, w h ile it s u ffe re d v ar iou s f a te s . O n the te c h n ic a l p lan e, the re are tw o p er iod s i n t h e his to r y o f r e s t or a tio n: th e firs t c om pr ise s m od ific at ion s o r re pa irs m ad e o n mo sa ics in the e ra w h e n mo sa ic w o rk w a s s till a n a nt an d a n a cti v e c ra ft. T he se c on d w h ich be g in s d ur in g t h e R e n a is sa n c e a n d c o n tin u e s t oth e p re s en t, c om p rise s res tor a tio n b y the "f o l-lo w e rs ; f ro m a ce r ta in t im e o nw ar d , t he y a t-te n d e d t o t he c o ns e rv at io n of m o sa ics , w hi c hh ad , w ith tim e, be c om e an ar tist ic a nd cu ltu ral h er itag e.

I t s ho u ld be m e n tio n ed h e re th a t m o -d e rn de co rat iv e mo sa ic w or k i s c a rri e d ou t w ithte c h n iq u e s a n d f or pu rpo se fa ir ly d iffer e nt fro m tho se wh ich , e s ta b lis he d i n a n tiq uit y, flou ris h e d du rin g t h e w h o le c o u rs e o f th e M id d le Ag es .

A m o n g t he va rio u s b o o ks on m o s a ic m a k in g ,o n its e x is te n c e th ro u g h h is to ry a n d th e h is to ry of m eth od s o f re sto ra tio n , a fe w dat e f rom th een d of t he la st c en tur y, tha t is , f r om th e tim ieo f th e f ir s t m o d e rn co nt r ov e r s ie s in th is f ie ld .T he in te re s t m o stl y d o cu m e nta ry of the s e b o o ks li e s p ri n c ipa lly in t he q u a lity of th e a uth or s;o n e w a s E d o u a rd G e rs p a ch , h im s el f a r es tor e rof m o sa ics (1) , th e o the r, P ie ro S a c ca rdo , p rot oof St . M ar k 's in Ve nic e, an d i n t h a t ca pa cit yd ire ct o r o f res tor a tio n w o rk a nd o f th e m o s ai c w or k sh op of the b asi lica (2 ). N o t on ly did th eyta ke a n in te res t iin th e h ist o ry a n d v ic iss itud es

2 0



o f m o s a ic s th ro u g h t h e c e n tu rie s , b ut th e ir e n -ga ge m e n t in t h e pr o m o tio n o f t h e [e a s t d e s tru c-t iv e m e an s of co n s e r vi n g th es e m o s ai c s w a s a c tive a n d c o m p e te n t. O the r w o rk s d e d ic a te d to m o sa ic s h av e s in ce a p p ea re d , w h ic h 'tre a t th e

hi s to ry o f t h e ir r es to ra tio n in di ffe re nt w ay s, bu t i t is th e de ba te s of th e s e c o nd h alf of th e1 9 th ce nt u ry w hi c h w ill o p e n th e w a y f or a ne wc on ce p t o f re s tor ati on (3 ).

I d o n o t p rop os e to s u m m a riz e h e re in de ta ilf a c t s w e ll do c u m e n te d in th is lit e r a tu re . I t i s o n o th er e xa mp le s tha t I w ou ld li ke to d we ll -e sp e ci a lly o n (a ) c e rt a in re st o ra tio n s w h ic h to o k p la c e in th e M id d le B y z a n tin e p e rio d , a n d w h ic h I h a v e o n o c c a s io n h a d th e p riv ile g e t o e x a m in e c lo se ly , a s w e ll a s o n ( b) ce rt a in m o r e re c e nt re s to ra tio ns o f t h e e n d o f th e 1 9 th a n d th e b e -g in nin g of th e 2 0t h c en tu rie s, wh ic h a re pe rh ap sm o re in te r e s ti n g to u s b e c a us e t h e y a r e h is -to r ic al ly c lo s e r a n d t h u s m or e in s tr u c t iv e a s reg ar ds th ei r p hi los op hy a nd th ei r w ea k po int s.I w ill try to p re se nt ab o v e al l e xa m p le s kn ow nt o m e firs t-h a n d a n d to s u p p o rt t h e m w ith t h e e vid en c e p ro vid e d b y illu st ra tio n s , w ith o u t the in te n tio n o f to u c h in g o n a ll th e c h a p te rs, m u c h les s a tte m pt ing to e x h a u sti v e ly c ov er th e s u b je cto f m o s a ic s . P lea s e f o rg iv e m y ra p id tr e a tm e nt o f th e v as t R o m a n c h a p te r , w h ich h a s be en t ra-d it io n a lly a n d s t il l is to d a y t h e s u b je c t o f n u -m e ro us s tud ie s ( 4) , a s w e ll a s th e m o sa ic s o fthe N or ma n kin g s o f S ic ily (4 a) .

O ur d oc um en ta tio n co me s m o s tly fro m fie ld r e s e a r c h c a r ri e d o u t o n a c e r ta in n u m b e r o f M idd le B y z a n tin e m o nu m e n ts am o n g th e m o st im p o rt a n t p re se rv e d a n d w hi c h da te fr o m t h e 1 1 th a n d t h e 1 2 th c e n tu r ie s ( 5 ) . T h is r e s e a rc h h a s al low e d t h e st u d y o f the te ch ni c a l a s p e c t o f a ll t h e s e m o n um e n ts , g et tin g to k n o w th ei r c h a -ra ct e r ist ics , a n d t he ir e x tr ao rd in a r y u n ity in s p ite of th ei r g e o gr a p hi c a l d ist a n c e fr o m e ac ho th er . I re fer to th e te ch nic a l u n ity c om m o n t om o sa ic s t h ro ug ho ut th e 1 1t h c en tu ry a n d t h ro u g h th e b e g in n in g o f th e fo llo w in g c e n tu ry , s ta rtin g fro m S t. S op h ia o f Is ta n b u l (6 ), p a ss in g t h ro u g h H o s io s Lo u k a s in P h o c is ( 7 ), S t . S o p h ia o f

K ie v ( 8 ), N ea M o ri o f C h ios ( 9 ), th e o ld er p a rt s o f S t. M ar k's o f V en ic e (10 ), To rc el lo (1 1 ), th eB as ilic a U rsi a n a o f R a v e nn a (1 2 ), th e m o sa ic s o f S t. M ich ae l o f K ie v (13 ), th os e o f S a n G iu st oo f T ri es te (1 4) , fi na lly , t ho se w hi ch re pr es en tth e ar ch aic tr en d in the c h u rch o f D ap hn i ( 15 ), inthe fir st ha lf of th e 1 2 th ce nt ur y . If t he s tyl e o fth e co m po si t io n s re co rd s v ar iat ion s an d e v o lu -t io n s w h ic h h e lp u s t o c o m p e n s a te s o m e w h a t, b y us e of typ o log y, fo r t he la ck o f a ny p rec is ed a te s f o r the se m o n u m e n ts , th e h o m o g e n e ity o f th e te c h n ic a l m e th o d s - fr o m th e s e tt in g o f the m o s a ic s in th e ir m o rt a r b e d to t h e r a n g e o f c o -lo ur s r ep re se nt e d in th

e g la ss p as te s o r in the n a tu ra l s to n e s - a s w e ll a s th e u s e f or ce rt a in fig u r es o f t h e s a m e , w el l - fix ed r e c ip e s , th is h om o g e n e ity th e n , m or e o r les s g e n e ral ly a s c e r-tain ed - bo th in te ch ni q u e a nd ty p o lo gy - all o w s

u s to d e fin e th e m o st im p o rt a n t c h a ra c te ri s tic s of th is c r af t f o r a g iv e n p e r io d.

J u d g e d b y th e s am e c r ite ria , a n o th er s e rie s o f B y z a n tin e m o s ai c s , s lig h tly l a te r , s h o w s te c h -n ica l t rai ts s o m e w h a t d iffe re nt fr o m th o s e w h ic h

w e h a v e g ro u p e d a bo ve . T he se m os ai c s a re p re -se rv ed in S t. S o ph ia of Ist an bu l ( 16 ), at Da ph ni (1 7) (i n t h e m os t a d v a nc ed te n d e n c ies o f t he wo rk sh op a ct ive th e re) , b ut a b o ve a ll a t S a int M a rk 's of V e n ice (1 8 ), e ls e w he re in th e lag o o n (1 9 ), a n d i n N o rm a n S ici ly (2 0 ). I f i t is p o s s ib le to d is t in gu is h fa irly c le a r ly o n th e te c h ni c a lp la n e b e tw e e n t w o g ro u p s o f m o s a ic s , n e a r t o e ac h ot h e r in b ot h tim e an d s p ac e, it is a ll th em o re so w h e n w e a re c o n fro nt e d w ith la te r in -terv en tio ns s ep ar ate d fro m th e e a rlie r b y ge ne -ra tio n s a n d b y c e n tu rie s . In o th e r w o rd s , re p a ir s a n d r e s to ra tio n s n e a rly a lw a ys b e tr a y th e m se lv e s to t he e x p eri en ce d ey e,

w h e th e r it i s a m a tte ro f B y z a n tin e o r o f W e s te rn m o s a ic s, d a tin g f ro m th e e ar ly Mi dd le Ag es o r f rom t he 1 4th c en tu ry. A r m e d w ith th is in s t r um e nt , t h e e x p e r ien ce d e y e , w e a re g o in g t o i d e n tify th e se c h a n g e s a n d th e ir m e th o d s of w o rk

A lw ay s, bu t e s p e cia lly d ur ing th e pe rio d of th e i co no cla s t s tru gg le s a nd a fte r the r es tor a-tio n of im ag es , s ev e ral m os ai cs ch an g ed pa rt c: f th ei r d e c o ra tio n for id eo log ic al rea so ns . S in ce it wa s so co st ly to re do a la rg e s ur fa ce in m o-s a ic s , it w a s c o n s id e re d s u ff ic ie n t , in c e r ta in c as es , t o d es tro y or re do , a cc or din gl y, on ly th e im a g e s , w h ile p re se rv in g t h e g o ld g ro u n d o r t h e g e o m e tr ic a l d e c o ra tio n s w h ic h w e re i d e o lo g ic a l-ly be ni g n . O f t h e fe w e x a m pl e s wh ic h h av e c o m e do wn t o u s, th e m o s t s pe cta c u la r - o r n ea rly -c o n c e rn s the m o s a ics (d es tro ye d in 1 9 2 2 ) o f t h e ch ur ch o f th e D o r m it io n i n N ic e a . In d e e d , t h e m o s t re ce n t d ec or a tion , w h ich r e p re s e n te d in t h e c on c h t h e s t an d in g V ir g in w ith t h e C h ild , v is ib ly rep la c e d t h e im ag e o f a c ro ss (w h ic h h a d be e n c ov e r ed b y g o ld cu be s, o n c e t he c u lt o f im a g e s h ad b e e n re- e s ta b lis he d. th e d ro ss its e lf re p lac in g in tur n an o lde r im ag e of th e V ir gi n d e s tro y e d b y th e ic o n o cl a s ts) (2 1 ).

A s im ila r c a s e is su sp ec te d ( for th e mo m en tw ith ou t c le ar a rch ae o log ic al ex ide n ce ) fo r the re p re s e n ta tio n of th e V irgi n i n t h e c o n c h o f S t.S o p h ia o f S al o n ica (2 2) a n d •al s o fo r t h e d e co ra -tio n of th e a p s id al co nc h of St . S op h ia o f Ist a n -b u l (23 ).

A p art fro m id eo log ic al str ug gle s, ot he r e ve nt sre q u ire d the p ar tia l r e p lac em e nt of c e rt a in d e-c o ra tio n s: s u c h i s t h e c a s e o f t h e im p e ria l p o r-t ra it o f Z o e an d o f tw o of he r h u sb an d s , w h o su cc ee de d e a ch ot he r b y he r s ide a s d o no rs at the c hu rc h o f S t. S op hi a o f Ist an bu l ( 24 ). Th em o s a ic p a n e l s itu a te d in t h e s o u th g a lle ry o f th e ch ur ch sh o ws c lea rl y a m o dif ica tio n ef fe c ti n g th

e id e n ti ty o f th e h us ba nd o f t h e em p re s s . T h e in sc ri p ti on n ex t t o t he f igu re o f t he e m p e ro rc on ce rn s C o ns ta nt ine M o n o m a c h u s; bu t t hi s in s c ri pt ion w a s i n s er te d l a t e r, in p la c e o f a n e ar lie r in sc rip tio n, an d th e s ub st itu tio n is v is ibl e

2 1



be ca u se o f c e rta in le tte rs w h ich a re m o re c los e -s e t t h a n th e o th e r s , i n a s p a c e c a lc u la t e d f o r a n o th e r n a m e . T h e h e a d o f t h e e m p e ro r w a s a p -p ar en tly r ed o n e c o m p le tel y in or de r to re pr es e n tM o no m a ch u s , w h ile k e e p in g t h e b o d y o f th e p re c ed in g em p er or . T h er e is in th e p a n e l a m y s -t e r y y e t u n ie x p la in e d co n c e rn in g th e s u t u r e s a ro u n d th e o th e r tw o h e a d s o f t h e p a n e l, C h ris t a n d Zo e . T h e tr a c e s s e em al s o t o in d ic a te a re s to ra tio n of th es e h e a ds . a ltho u g h t h e re a so nfor t h is o p er at io n is n o t a t p re s e n t c le a r. A n -o th e r e x a m p le o f d e c o ra tio n s w h o s e p ro g ra m m e w a s m o d ifie d a s a re s u lt o f p o litic a l c h a n g e s is fo u n d at R av e n n a , in t h e m o sa ic s of S t. Ap o lli -n a re N u o v o , , w h e re s c e n e s o rd e re d b y T h e o -d or ic , k in g of th e G o th s. w e re e ra se d b y hi ssu c c e ss o r i n the d e co ra tin g o f t he c h u rc h , t he B is h o p A g n e llo (2 5 ) .

F in all y, in th e co u rs e o f ca m pa ig ns o rg a niz e d

in th e Ve n et o, s ca ff ol di ng c o ns tr uc te d a t S t. M a rk 's h a s p e r m it t e d u s t o s tu d y c lo s e ly a n d to d e m a rc a te i n t h e e a s te rn c u p o la tw o p h a se s in th e d e c o ra tio n o f th e m o s a ic s re p re s e n tin g th e P ro p h e ts a n d th e V irg in ar ou n d C h ris t E m -m a nu e l. T h e s e co n d p h a s e s e em s to b e th e c o n -s e q u e n c e o f th e d e s tr u c tio n b y a n e a rth q u a k e o f t h e o r ig in a l m o s a ic s . T h e s u t u r e d iv id in g t h e P ro p h e ts in tw o g ro up s pa s se s th ro ug h th e fie ld o f g o ld w h ic h e x te n d s b e tw e e n t w o fig u re s , in t h e m id d le o f a n i n s cr ip t io n w h ich c o n t in u e s , u n c h a n g e d , e x c e p t f o r th e c o lo u r o f th e c u b e s : b la ck o n on e si d e , d a rk bl ue o n th e ot he r. W er eit n o t fo r th e ch a n g e in s tyl e (a c lea r in di c a tio n o f t he t im e la p s e be tw e en t h e tw o p ha se s ), an d a ls o fo r t h e in tr o d u c tio n in P h as e II of a s u p pl e -m e n ta ry fi gu re , w h ic h re d u c es t hi e fre e sp a ce be tw e e n th e fig u res o f t hi s p h as e (2 6) , th e o v e ra llp ro g ra m m e a n d th e c o m p o s itio n o f t h e d e c o ra -tio n a s w e s ee t he m , ( it all d at e s fr om a b ou t th e m id dle o f th e 1 2 th c e n tu ry ), fol lo w an d r es to re th e o r igi n a l d e c o ra tio n , o ld e r b y ha lf a ce n tu ry .

'A g re a te r s u rp ris e a w a ite d u s w h e n w e e x -a m in ed t he m o s ai cs o f To rc e llo . Al th ou g h ac h ro n o lo g ic a l d iffe re n c e h a d a lre a d y b e e n n o te d w it h in t h e m o s a ic s d e c o r a t in g th e m a in a p s e (o n th e on e h an d th e Ap o stl es o f t he h em icy cl e,

p ro d u c ts o f a n e a r lie r p e rio d, o n th e o th e r h a n d th e V irg in in t h e a p s e an d th e A n n u n c ia tio n , re -s ul ts of a la te r re s to ra tion m o re t h a n a ce n tu ryd is ta n t fro m t h e A p o s tle s ) , t h e e x a m in a tio n o fth e w e s ter n w al l (d e co ra te d , it s ee m e d , in o ne b re a th , w ith m os a ic s t ha t w e re k n ow n to h a ve be e n re s to re d in th e 19 th c en tu ry , a n d w h ic h re - p re s en t th e C ru c ifix ion , th e A n a s ta s is a n d t h e Las t J u dg e m en t) (2 7 ) a llo w e d t he d is co v e ry o fa v e ry fin e re st or at io n o f th e or ig ina l co m p o s i-tio n . T h e wo rk s h o p ac tiv e in th e re s tor at io n c a nb e d a te d b y i ts s ty le t o the e n d o f th e 1 2 th c e n -tu ry . C a lle d u p o n to r e p a ir c o n s id e ra b le d a m a g e s u ffe re d b y t he m o sa ic s, th is w or ks h o p re m a d e to a g re at e xte n t t he e a rlie r de c or at io n s , w h ile re s p e c tin g th e fo rm e r m o d e l e v e n in its d e ta ils , es p ec ia lly w h er e th e da m a ge c u t t h r o u g h t he

m id d le o f a s c e n e . W h e n it w a s n e c e s s a r y t o re d o a n e n ti re g ro u p o f p e o p le - th e A p o s tle s ,J u d g es o n o u r rig h t - c e rt ai n d iffe re nc es i n s ty le b e ca m e m or e vi sib le a t To rc e llo a s the y d id in th e e a s te rn c u p o la a t S t. M a rk 's .

T he s e las t e x am p le s, la ck in g a n y id e o lo g ic a l o r po lit ica l m ea ni ng , p ro v e cle a rly th e a rc ha e o-lo g ic al a tt itu d e o f th e te a m e n tr u s te d w ith th e rem a k ing o f the d e str oy e d m o s a ic s , w ith o ut ta k-in g in t o a c c o u n t th e f a c t t h a t to c o m p le t e th e m is s in g p a rts o u r m o s a ic is ts w e re fa c e d o n th e t e c h n ic a l l e v e l w it h a ro u t in e p ie c e o f w o r kw hi c h th e y a c c o m pl ish e d w ith no d iffic u lty. T hi s is b e c a u s e in th e M id d le B y z a n tin e p e rio d the

n w m o sa ic is ts, th e re st or er s, st ill un d er sto o dth e ir e ld e rs (o f w h om th e y w er e th e s u cc es s o rs )d o w n to t h e la s t n u a n c e . T h e y k n e w e q u a lly w e ll th e ic on o g ra p h ic th e m e s th e y h ad t o c o m pl et e a n d s tr o v e t o k e e p a c e rt a in s ty lis tic d is c re tio n , ren d er ed f a ir ly e as y by t h e ir es s e n tia lly s im ilar tec hn iq U e. A t t h e ir be s t, t he s e p a rts a dd e d lat er c an n ot b e id e n ti fie d e x c e p t w it h th e a id of r e -s e a rc h c a r r ie d o u t o n th e m o rt a r b e d i n w h ic h t h e t e s s e ra e a r e im p la n te d . T h e m o r e r e c e n t m o rt a r ap p ea rs c le a rly d e m ar ca te d in re la tio n to the e ar lie r be d , a nd t he d iffe re nt co m p os ition s o f th es e m o r ta rs i s e v id en c e of th e le n g t h of t im e b e t w e e n th e tw o p ha s es . Li t tle b y li ttl e, h o w e v e r, t h e r a n g e o f m a te ria ls u se d (g la s s a n d s to n e s ) s lo w ly ch a n g e d , a n d a t th e e n d o f th e M id d le A g e s th is c h a n g e , w h ic h w a s b e c o m in g m or e an d m or e ev id en t, w en t h a nd in h a nd w ith in c re a s in g m o d ific a

tio n s o f t h e s ty le .T h e c o n q u e s t o f t h e B y z a n tin e E m p ire b y t h e T u r k s p ut a n en d to a n a rt w h ic h h a d la r g e ly s e rv e d to d e c o ra te m o n u m e n ts o f th e C h r ist ia n c u lt. T h e a b se n c e o f i m p o rta n t p at ro ns p re ve n t-e d its c o n t in u a tio n in o t h e r p a rt s o f E a s t e r n E u ro p e . I n Ita ly , in R o m e a n d F lo re n ce , a fte r th e g re a t de ve lo pm e n t o f t he 1 3t h a n d 1 4 th ce n tu rie sw he n o ld m o s a ic s w e re r ed o ne a nd o th e r m o -s a ic s f lo u ris h e d in a la s t b u rs t o f t h is t ra d itio n a la rt , p a in t in g to o k o v e r fo r g o o d . T h e R e n a is -s a n c e w a s to r e le g a te m o s a ic s t o a n a ux iliar yra n k in t h e s e rv ic e o f a d iffe re n t p la st ic co n c e p -t io n . T h e la s t g r e a t m o s a ic is t s w er e a ls o t h e fir s t pa in te rs o f t h e R e n a is s a n c e. W h e n a G io tto or a P ie tro C a va lli n i u s e d m o s ai c s a s a m e a ns o f ex p re s s io n , o n e c an u n d e rs ta n d w h y n e v er ag a in co u ld tra d itio n al m o sa ic s, in th e G ree k m a n n e r, re g a in th e ir i m p o r ta n c e . O f C a v a lli n i, V a s a r i sa id , a pr op o s th e fo rm e r fa c a d e o fS t. P a u l's o u ts id e -th e -w a lls, th a t h e h a d a lik in g fo r th e o ld G re e k m a n n e r , w h ic h h e m ix e d w ith th e s t y le of G io tt o " .

A lth o u g h o n e c h a p te r in th e h is to ry o f m o -s ai c s h ad j u s t e n de d , t h is a rt n ev e rth e les s d idn ot d isa p pe ar . I ts d ev el op m en t co nt in ue d in pa -ra lle l d ire c tio n s in R o m e a n d in V e n ic e . In t h e la tt e r c ity , o n c e th e B y z a

n tin e s c h o o l w a s e x -tin g u is h e d , m o s a ic w o rk b e g a n a g a in in th e 1 5 th c e n tu ry w ith th e d e c o ra tio n o f th e c h a p e l o f th e M a do n na d e i M a sc o li. W h e n w e lo ok a t th e s e

2 2



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m o s a ic s fo r w h ic h F lo re n tine ar ti st s h ad be e n su mm on e d, we are st ruck by the di s tan ce s ep a-r a ti ng th e m f ro m th e f irs t d e co r a ti on s o f th e ma in p or ta l o f S t . M ar k 's . W ith th e p a s sa g e o ftim e, e ar t hq u ak es , fir e s a nd ot h er c a la m itie s ,p a rt s o f th

e o ld m os a ic s w e re de s tr o ye d a n d h ad to b e res tore d: for e xa m p le, the Ch rist En -th ron e d o f th e m a in a ps e , m e n tio n e d in c h ro -n icle s a s ha vin g s u ffe red da m a g e a s a re s ul t of two m a jor fire s w hic h h a d r av a ge d t h e B as ilic a in 1 41'9 an d i n 1 4 89 . T h e m o s aic wa s r edo ne , c om pl e te d in 1 5 0 6, a s is a tte s ted by th e si g na -tur e o f th e m o s a ici s t P e tr u s (28 ) . it i s in te res t-in g t o n o te t h at t he C hr is t o f P e t ru s c o pi es in al l de tai ls o f s tyle a pro tot ype th at o ne ca nc le ar ly p erc eiv e a n d w hi c h c an be da ted to th e 1 .2t h ce ntu ry. O th er m os aics of St. Ma rk's red one in th e 1 5th ce n tu ry a lso bea r w itne ss to a de sire to p re s er ve t h e e ar lier c om po s it io n a s fa ith ful ly

a s p oss ible .I n th e 1 6t h c e n tu ry , t h is r es p e c t fo r th e

o rig inal wo rk w as co m pl ete ly s ubm er g ed by the imp etu s o f g r ea t V e ne tia n p a in t ing . M os a ic s be cam e a n inst rum en t in the ser v ice of pa intin g,w h ic h w a s ii n ev itab le w h e n a t S t. M a r k's the ca rtoo ns w e re th e w or k of Tit ia n, Ve ron e se , Ti n -to ret to , o r e lse , at R o m e , of R ap h a e l. A s a re s ult o f th e d eb a te s b e te e n two riv al fac t ion s w ho wo rke d in the B a sil ica dur ing the 16 th c en tury ,w e k no w s om e o f th e m e th o ds by wh ich t he mo -sa icis ts o f S t. M ark 's e xe c ut e d m os aic s fo llo w -in g c arto on s . T he mo s aic ists Ba rto lom eo Boz za a n d th e B ian c hi n i b rot h er s de n o u nc e d th e Z u c -c at o fa m ily , t h ei r co m p e ti to rs at S t. M a rk' s , t o the Pr o cu rato r in ch arg e o f F ina n ce , a c cu s in g

th e m o f h av in g r en d e re d ce rta in o b je ct s in p a in t-ing an d n o t i n m o sa ics . Th e t r ibu n al , fo rme d b y Ti tian , Pa olo Ve rone se , Tin tor e tto , Ja c op o P isto iaan d A ndr e a S ch iav o ne , fa vou red the sid e o f th ea cc u s ed , o f w ho m T iti a n w a s a lo n g -s ta n d in gfri e nd a n d a lly . H e h im s el f bo re w it

n es s a sha v in g fu rni s he d d raw ing s to Zu cc a ti a nd f in a l-ly t h e B ia nc h in is h e a rd t he m s e lv e s a c c u se d b y T in t ore tto of fau lts ( of form a n d p ro p o rt io n ) i n ce r ta in d raw ing s a n d b y T itia n o f a di s ho n ou r-a bl e bo rde r . T hi s ha pp e ne d in 15 6 3 (2 9) .

T h e Z uc c a tis w el l k n o w n a t th e tim e, c e le -b ra te d b y V as a ri , ha v e le ft u s e n o rm ou s s u r-fa c e s de c o ra te d b y th e m in S t. M a rk's , th e f ru ito f a c ol le ct iv e w o rk o f s e ve ral d e ca d e s. T h e ir m o sa ics o fte n t o ok the pla ce of t h e o ld m o s aic s,no lo n g e r t o t h e ta s t e o f th e p ai n te r s o f t h eR e n a iss a n c e. t i s sa id t ha t it w a s T it ia n w h op ro p o s ed ha v in g th e o ld m o s aic s r e pl a ce d b y n e w o n es i n th e c u rr en t ta s te , wh ich w a s d o n e, b e gi nn ing w ith t h e a tr iu m i n 1 53 0 , a t t h e le ve l o f th e c lere sto ry ( 30) .

It w as on ly in 16 10 tha t th e V e ne tian go ver n-m e n t be g an to wo rry a bo ut the c on s erv atio n of the ex isti n g m o s aic s a n d , by a d ec ree , to se -v e re ly c o nd e m n th e d e p lo ra b le a b u se of d is a s-s em bl in g t he old m o sa ic s in o rde r to ma ke n e w o ne s . A n d in t he ca s e w he re r e pl a ce m e n t w o ul d b e in e vi ta b le b e c a us e o f th e p o or s ta te o f t h em o s ai c , a ve ry e xa c t d raw ing w a s t o b e m ad e so a s to r e do the wo rks in t h e s am e m an n er (31 ).We kn ow on e of the se dra win gs m a d e b etw ee n

16 11 a nd 16 1 7 , wh e n the old Co m m un io n o f t h eA pos tle s on th e e a st wa ll o f th e n o rth tra ns e pt w as re pl ac e d b y th e s am e c o m p os itio n fo llow ing a c a rt oo n o f A lien s e. Th is d raw ing (F ig. 1 ), to-

F ig. 1 - Ven ice , Ar chiv io d i St ato , dra win g o f th e or igin al c omp osi tion on the eas t w all o f th e no rth tran se p t o fSt . Ma rk's be fore it w as r epla ced by the pre sen t wo rk

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g e t h e r w it h t h e r e s u lt s o f t h e s u b s ti t u t io n s t il lv is ib le t o d a y , a n d w ith a ll th e o th e r m o s a ic s re -p la c e d in th e 1 7 th c e n tu ry , b e a rs w itn e s s to th e e n o r m o u s d iff e r e n c e s e p a r a ti n g t h is m o s a ic -p a in ti n g fro m w ha t w e u n d e r s t a n d t o d a y a s are s to ra tio n . H o w e v e r , th e k n o w le d g e o f th is

d if-fe re n c e w a s to t a k e h o ld in th e m in d s o f a f e w e n lig h te n ed p e rs o ns , w o rri ed to s ee th e di sa p -p e a ra n c e o f v e s tig e s o f fo rm e r tim e s . Little b y litt le , t h e c o n c e p t o f re s to r a t io n it s e lf w a s t o b e m o d ifie d b y th is , a n d in tw o d ire c tio n s . F irs t, b y th e re m o v a l o f e n d a n g e re d m o s a ic s t o o th e r a rc h itec tu ra l s up p or ts . N ex t by t h e co m p lie tio na n d th e r e p a ir o f t h e ru in e d p a r ts o f m o s a ic s ,fa ith fu lly im ita tin g t he s ty le a n d th e t e c h ni q u e

o f t h e s e w o rk s. T h e p h ys ic a l t ra n s fe r o f o ld m o s a ics a ls o h a s

it s h is to r y , w h ic h b e g in s w it h t h e m o s t s im -p lis tic m a n ife s ta tio n s , i .e . th e d e s tru c tio n o f m o-s a ic s in o rd e r to r e c u p e r a t e th e m a t e ri a ls . W rit te n s o u rc e s a tte s t to th e t ra n s p o rt a tio n o f m o s a ic s fr om R a v e n n a to A a ch e n b y C h ar le -m ag n e, w h o w an te d t o de c or a te h is c hu rc h w ithth e m (3 2 ); th e re u s in g o f a ll k in d s o f m a te ria ls -in c lu d in g m o s a ic s - b y B as il I in th e d e co ra t io no f h is N e a E k k le s ia (3 3 ); o f t h e de s tr uc tion s o fw h ic h th e P a tr ia rc h M ic h a e l C e ru la riu s w a s a c -c u s e d , w h o , i t i s sa id , d ri v e n b y h is a v a r ic e ,s t r ip p e d c h u r c h e s o f t h e ir m o s a ic s a n d u s e d th e m fo r h is w o rk s (3 3 a ); l a s tly , to th e tra n s p o rt b y t he V e n e tia n s , i n th e ir s h a r e o f t h e b oo t y a fte r th e F o u rth C ru s a d e , o f m o s a ic s a n d o th e r d e co ra tiv e m at er ia ls fr o m C o ns ta n tin o p le to V e

-n ic e ( 3 4 ) . I n a ll th e s e e xa m p le s w e a re d e a lin g w ith t h e t ra n sp o rt o f m o s a ic te s se ra e , ra w m a -te ria ls in g la s s p a s te a n d p e rh a p s in fin e m a rb le .

A n e x a m p le o f a m o re c o m p le x tr a n s p la n ta -ti o n o f a n o ld m o s a ic in to a r e n e w e d c o n t e x t co u ld h av e b e en t he h e a d of C h ris t (d a tin g fr om t h e 4 th o r t h e 5 th c e n tu r y ) i n th e a p s e o f S t. J o h n L a te ra n d u rin g t h e r e s to ra tio n u n d e r-ta k e n t h e r e b y T o r r it i a t t h e e n d o f t h e 1 3 t h c e n t u ry . H ow e v e r, th e d e st ru c tio n o f th e o ld m o s a ic in 1 8 8 4 a nd its r e p la c e m e n t w ith a c o p y d o es n o t, un for tu na te ly , a llo w u s ev e r to re s ol ve t h e m o d e r n c o n tr o v e r s y o n t h e n a tu r e o f t h e

o p e rat io n : w a s th e h e a d o f C h ris t re a lly s a ve d b y T or rit i a n d in c or po ra ted in th e re n ew e d a ps e ,o r w as i t o n ly a c o py , se p a ra te ly w o rk e d in t he m a n n e r o f a n e m b le m a , th u s e x p la in in g th e a u to -no m o u s m o rta r b e d o n w hi ch i t w a s fo u nd a t th e e n d o f th e la s t c e n tu ry (3 5 )? i t s e e m s al so t h a t re p a irs o n th e m o s a ic s o f S t. P e te r's u n d e rta ke n b y In n o c e n t II I a t th e e n d o f t h e 1 2 t h ce n tu r y , re p re se n t a re s to ra tio n in t h e s e n s e t h a t th e o ld p a rt s w e re p re s e rv e d in p la c e , in s te a d o f b e in g c o m p le te ly re m a d e . W e c a n n o lo n g e r ju d g e in w h a t m e a s u re th e m o s a ic s of S t. P a u l's o u ts id e -th e -w a lls , re s to re d a fte r 1 2 1 8 u n d e r t h e a u s p ic es o f th e s a m e po p e , w e re in s p ir ed b y , c o p ie d, o rin c o rp o ra te d t h e m o s a ic s o f th e 5 th c e n tu ry b e -c au s e th e p re se n t d e co ra tio n da te s fr o m a ro u n d 1 8 2 3 . A m o n g t h e o ld e s t r e s to ra tio n s s till v is ib le

to d ay a re th o se i n S O Me p a n e ls in th e n a v e o fS a n ta M a ria M a g g io re (3 6 ) .

L a t e r , a ls o i n R o m e , s e v e r a l m o s a ic fr a g -m e n t s w e r e r e m o v e d fr o m t h e ir a rc h it e c tu r a l fra m e w o rk m o re o r le s s s u c c e s s fu lly . T h e o nl yf ra g m e n t s p re s e r v e d fr o m th e o ld c h u rc h o fS t . P e t e r 's d a te f ro m t h e re s to ra ti o n of I n n o -c e n t I II, c ite d a bo v e , a n d w e re de ta c h e d in 1 5 8 2o n t h e o c c a si on o f t h e d e s tr u c ti o n of t h e o ld b a s ilic a . I n th e s a m e p e rio d , b e tw e e n 1 6 0 9 a n d 1 6 3 1 , t h e m o s a ic fr a g m e n t s o f t h e o r a t o r y o f J o h n V II w e re a ls o r e m o v e d . T h e te x tu re s w e re d a m a g e d in a ll th e s e c a s e s , to d iffe re n t d e g re e s , a n d a lth o u g h th e i c o n o g ra p h ic in te re s t o f th e s e f r a g m e n t s is in c a lc u la b le , t h e ir s ty le h a s lo s tm a n y o f i ts d is tin c tiv e q u a litie s . T h e N a v ic e lla o f G io tt o , a s w e s e e it to d a y , d a te s fr om th e 1 7 th c e n tu ry . T o re p la c e th e o rig in a l, d e s tro y e d m o s a ic , i t w a s re d o n e fro m a life -s iz e c a rto o n e xe c ut e d in 1 6 2 8 . T h e a n a ly s is o f th is m o s a ic ,w ith its ' s u c c e s s iv e la y e rs o f m o d ific a tio n , h a s c a u s e d m u c h in k to flo w .

A m o re s u c c e s s fu l e x a m p le o f t h e re m o v a lo f m o s a ic f ra g m e n t s fr o m th e ir o r ig in a l fr a m e is pr o v id e d b y th e he a d s o f s a in ts a n d th e fi gu reo f a s ta n d in g o ra n t V irg in , i n th e m u s e u m o f t h e a rc h b ish o pr ic o f R a ve n n a . T he s e fra g m en ts c o m ef ro m t h e fo r m er c h u r c h o f t h e B is h o p U r s u s ,re d e c o ra te d w ith m o s a ic s in 1 1 1 2 a n d d e s tro y e d b e tw e e n 1 7 3 4- 1 7 4 5 to m a k e w ay f o r a n e w c o n -s t r u c t io n ( 3 7 ) . In a d d it io n t o a d r a w in g o f t h e e n tir e c o m p o si tio n , th e m o s a ic s (d e ta c h e d fro m

th e w a ll, p re s e rve d in w o o d e n cr a te s , th e o n ly 'e v id e n c e o f th is d e c o r a t io n a n d th e o n ly e x -a m p le in th e n o rth e rn A d ria tic a re a d a te d b y a n in s c r ip tio n ), h a v e c o m e d o w n t o u s i n a n e x c e l-le n t, a lm o s t i m p e c ca b le s ta te .

A tt e m p ts a t t ra n s p o rtin g a m o s a ic c o m p o s i-ti o n in i t s e n t ir e t y fr o m o n e p la c e to a n o th e r a re k n o w n o n ly f ro m t h e 1 8 th c e n tu ry o n . T h e m o s a ic o f th e t r ic lin iu m o f th e La te ra n P a la c e , d e ta c h e d fro m i ts a p s e u n d e r C le m e n t XII ( 1 7 3 0 -1 7 4 0 ), f e ll i n to fr a g m e n ts im p o s s ib le to p u t to -g e th e r a g a in . I t w a s c o m p le te ly re m a d e u n d e r P o pe B e n ed ic t X IV in 1 7 4 3 in th e p al ac e s qu a re w h e re it is v is ib le to da y . T h is ‘vo rk , ca rrie d o u tu n d e r t h e d ir e c t io n o f C r is t o fa ri , h e a d o f . th e p o n tif ic a l m o s a ic w o r k s h o p , is e x t r e m e ly m e -d io c re a n d p re s e rv e s o n ly th e ic o n o g ra p h y o f th e o rig in a l.

In t h e 1 9 t h c e n tu r y , th e o p e r a ti o n w a s a t-te m p te d o n a la rg e r s c a le , in o rd e r to m o v e th e a p s id a l m o s a ic , b o u g h t a t a u c tio n b y t h e c ro w n p r in c e o f P r u s s ia in 1 8 3 7 , fr o m t h e c h u r c h o f S t. C y p ria n i n M ur a n o ( F ig s . 2 , 1 1 ) to t h e F riie -d e n s k irc h e in P o ts d a m (3 8 ). T h e m o s a ic w a s c u t in to sq u a re s n d w o r k o n it c o n t in u e d fo r tw o y e a rs . Th e r es u lts o f th is fi rs t s u cc e ss fu l s tr a p p o a re s t ill, h o w e ve r , a lo n g w a y fr o m t o d a y 's r e q u ir e m e n t s

a n d t h e in t e r v e n ti o n o f m o d e r n m o sa ic is ts is to o v is ib le . A n o th e r a p s id a l m o -s a ic , b e lo n g in g to th e c h u rc h o f S a n M ic h e le in A fri c is c o , R a v e n n a , w a s m o v e d a t th e s a m e

4



Fig. 2 - Potsdam, Friedenskirche, general view of the mosaic from the ancient chuch of St. Cyprian in Murano

25



F ig. 3 - R em ov al o f t he m o sa ic an d o f th e firs t la ye r o ft h e s u p p or t, r e v e al in g t h e s e c o nd la y e r w it h i ts in d e n ta t io n s fo r h o ld in g t h e m o r ta r m o r e s e cu r e ly

F ig . 4 - T he s to n e s o f t he w a ll its e lf a re re v e a le d w he na ll t he m o rt a r h as be en re m o ve d

F ig. 5 - Th e n ew m ort a r b ed is rea dy to rec eiv e t h emo sai c

Fi g . 6 - T h e m os aic a fter be ing p u t b ac k i n p lac e

F igs . 3- 8 - Se rie s s ho w in g t he di f fer e n t ph as es of the s trap po me tho d ( he re p ra cti s ed on th e m o s ai c s in t h e no r th ap s eh em ic y c le o f S an G iu s t o, T r ie s te i n 1 9 4 7 )

2 6



Fi g . 7 - Ba ck v ie w o f th e d e ta c h e d m o s a ic w it h t h e m o rta r r e m o ve d

F ig . 8 - T he re mo va l o f th e m o s ai c s, su cc e ss ive la ye rso f m o r ta r , a nd th e c le a n in g of th e u n d e rl y in g m as o n r y, b ro ug ht to lig h t a s e rie s o f w in do ws w hi c h e xi s te d b efo re the pr es e nt m o sa ic d ec or a -tio n o f th e ap s e

t im e , a n d a p p ro x im a te ly in th e s a m e m a n n e r , t o t he B e i-li n m u se um . A f te r a lo ng w a it a n d m a n y m is h a ps , i t w a s re co ns tr u c te d o n

ly a t th eb e g in n in g o f t h is c e n t u r y , w ith s im il a r r e s u lts (3 9 ) . F o r t h e m o s t p ar t , it i s a m o d e r n re co n -s tru c tio n .

Th e tec hn iq u e o f m o s a ic r e m o v a l, in its e a rly s tag e s i n t h e e x a m p le s g iv e n a b o v e , c o n si s ts in d e t a c h in g t h e m o s a ic fro m it s s u p p or t i n o rd e r to cle a n a nd c on so lid at e t he w al l a n d /or t he la ye rs o f m o r ta r w h ic h h ol d it t o t he w al l,a n d th e r e a p p lic a tio n o f th e m o s a ic o n a ne

w , s ou nd b ed (F ig s. 3- 8 ). U se d o n la rge s ur fac es d u r in g th e g re a te r p a rt o f t h e 1 9 th c e n tu ry , a n d s t il l in t h e 2 0 t h , r e c o g n iz a b le b y it s g r id o f

s e a m s , th is te c h n iq ue h a s im p ro v e d g re a tlys in c e it s b e g in n in g s , t o t h e p o in t w h e re t o d a y it n o l o n g e r le a v e s t h e m a rk o f t h e s q u a r e s w h e n p u t b a c k int o p la c e . T h e s tra pp o tec hn iqu ene ve rth el es s h a s o th er di sa dv an tag e s, ma in lyth e g e n e ra l a p p e a ra n c e o f th e s u r fa c e a fte r i th a s b e e n r e m o v e d fro m its s u p p o rt a n d pu t b ac kin p la ce . T h e t e x tur e s u ffe rs a l a c k o f c oh es io n .

B es id e s m o v ing m os ai c s, it wa s oft en n e c e s -s a ry to r e d o o r res to re pa rtl y d am a g e d m o sa ics

w ith o u t r e m o vi n g th em . T h e a r c h a e o lo g ic a l s oli cit ud e of the m o sa ici st as re sto re r a p pe ars fa ir ly e a r ly in ce rta in ca se s, su ch a s a t T o rce llo ,for w h ic h a d o cu m e n t d a t ed 1 75 7 a llo w s th e pla ci ng o f a na m e on th e rep a irs - c le ar ly se t-t e c e n t es ch i - s ti ll v isi b le in t h e C h a p e l o f th e H ol y S ac ra m e n t. P ie tro M on ac o is d o c u m e n ted a s h a vin g re m a d e t w e nt y -f ive s q u a re V e n e tia n fe e t o f m o s a ics a t T or c e llo an d as h a v ing c o n -s ol ida te d an d w a sh e d o n e h u n d re d a n d f ifty ot h e rs (4 0 ). In 1 7 5 1 h e sig n e d hi s n am e u n d e rthe m o sa ic of Da ni el, in th e sc en e o f S u sa nn aan d th e E ld e r s, o n t h e w es t w a ll o f t he n or th tr a n s e p t o f S t . M a rk ' s . It i s i n te re s t in g t o n o te the d o u bl e s ta n d a rd u s e d by M o n a c o : D a n ie l,ne wl y e xe cu te d , is a p os t-R e n a iss an ce p ain tin gre n d e re d in .m o s a ic s , w h ile th e fr a g m e n ts a d d e d a t T or c e llo to co m pl e te m o s a ics o f th e By za n -tin e p e rio d , fo llo w e d th e ir s c h e m a s a n d r u le s .H o w e v e r, b e s id es M o n a c o 's in a bi lity to re st o re th e te xtu re o f th e su rfa ce c ov er ing It w ith co m -p ac t s m al l te ss e r ae i n t he m an n e r of th e o ld m a s te rs , h e a ls o u s e d th e s a m e m at e r ia l in T o rce llo th a t h e u s e d f o r h is D a n ie l in S t. M a rk' s .T h e w h it e , c y c la m e n , r o s e a n d g re e n g la s s p a s te , fo re ig n to th e o r ig in a l p a le tte . o f th e T o r-ce llo m os ai c , a n d l e ss c a re fu lly cu t, a ls o b e tra y s

th e p e rio d o f th e re s to ra tio n .W e k n o w th at a ce rta in Le op ol d o d a l P o z z o ,

a R o m a n m o s a ici s t w o rk in g i n S t. M a rk 's b e t-w e e n 1 7 1 5 a n d 1 7 4 5 , e x e c u te d th e S t. J e ro m e o n t h e n o r th - w e s t p e n d e n t iv e o f t h e n o rt h e r n c u p o la . H e w o rke d fro m a c a r to o n b y P ia z z e tt a an d . in th e s ty le of th e p e r io d . T o th e s a m e d al P o z z o , s a id t o be a re s t or er (4 1 ) , w e c o u ld pe rh ap s a sc rib e th e s ym b ols o f t he fo ur E v a n-g e lis ts in th e s a m e c u p o la , in t h e 1 2 th c e n tu ry s ty le , w hi c h do n o t se em t o h a v e ex is ted o r ig -in al ly, an d the re st or ati o n of pa rts o f th e or igi na lm o s a ic s o f t h e 12 th c e n tu ry . T h e res to re d s ec -ti o n s (i n th e s c e n e o f th e d e s tr u c t io n o f

t h e te m p le o f D ia n a , in th e f igu re o f S t: J oh n as a n o ra nt, et c.) g en er all y f oll ow th e me d iev al te ch -ni c a l fo rm ul a e . O nl y u po n c lo se a n a lys is c a n w e

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id e n ti fy e rr o r s o f in t e r p re t a ti o n i n t h e r e c o n -s t r u c t io n o f t h e m o v e m e n t s o f t h e f ig u r e s , o r m a r k e d d iffe r e n c e s b e tw e e n th e c o lo u r s o f c e r -

t a in m a t e r ia ls u s e d b y th e tw o w o r k s h o p s . A l-t h o u g h le s s e v id e n t th a n in t h e r e s t o r a t io n s o fP ie tro M o n a c o , t h e s e d iffe re n c e s p ro v id e a fa ir ly

2 8

F ig . 9 - S er re s , M e tr o po le, a p s e m o s a ic n o w t ot a lly d e s tr o ye d . C o m m u n io n o f th e A p o s tl e s , D e ta il: n o t e th a t th e is s in g p a r ts o f t h e m o s a ic h a v e b e e n r e p la c e d b y p a in t



Fig. 10 - TorceJlo, Santa Maria Assunta. Anastasis, detail:Archangel Gabriel

Fig. 11 - Potsdam, Friedenskirche. Mosaic from the churchof St. Cyprian in Murano, detail: Archangel

Michael

certain guide to recognizing dal Pozzo's work.So does the use of a stucco” setting bed whichdal Pozzo brought from Rome and which goesback as far as the end of the cinquecento. Con-sisting of the use of an oil mastic in place oflime cement for the mortar bed of the mosaics,this process had the advantage of slow dryingbut also the disadvantage that the oil stainedthe stones. It was theoretically abandoned atSt. Mark's shortly after the disappearance of dal

Pozzo (42).Toward the beginning of the 19th century,

an interest in the old, original mosaics develop-ed. The crown prince of Prussia set a goodexample, as we have seen above. In Russia in1843, while Solnzeff, of the Academy of FineArts of St. Petersburg, was restoring the fres-coes of St. Sophia in Kiev, 11th century mosaicswere discovered under a layer of plaster andoil overpainting (43).

The discovery of the mosaics of St. Sophiain Constantinople followed closely when theFossati brothers were called by the sultan to

strengthen the monument. They were astonishedat the state of conservation of these mosaicsand moved by their beauty. On the orders ofthe sultan, for religious reasons, they wereforced, however, to cover them with plaster

but not without first having taken abundantnotes, in the form of drawings (44). The Byzan-tine mosaics in Greece and Turkey had survivedmore or less intact under their layer of plaster,suffering only the injuries of time (Fig. 9). It wasnot until the end of the 19th century that theywere to become a training ground for restorers.

Italy, on the other hand, remained the onlycountry where the mosaics in functioning chur-ches were constantly maintained. As early as1727, in the time of Benedict XIII, a workshopexisted in the Vatican, La Reverenda Fabbrica diSan Pietro. When it started, it was meant toreproduce famous paintings in a more lastingmaterial. Napoleon, at the beginning of the 19thcentury, encouraged the art for the decorationof public buildings, as did the czar of Russia.In 1803, Napoleon organized a school for mo-saicists in Milan in which Vincenzo Raffaelliwas among the teachers. One of his pupils,Giovanni Moro, was to leave his mark on allmosaic restorations in St. Mark's through 1858.Although the few firms patronized by the state

were mainly occupied with the production ofmodern mosaics, there were other private work-shops of varying sizes flourishing almost every-where in Italy.

In a way, these workshops, among which we

29



mu s t a lso c ou nt th e V a tic an 's , b y t he ir m e th od o f w o rk in g b ro u g h t a b o u t th e ru in of th e v e r y m o s a ic s t h e y w e re s u p p o s e d to r e s to re . R a re a re th e Ita lia n m o n um e nt s t ha t e s c a p e d th isfate . Fo r R o m e a n d its su rr ou nd in gs , t he a r-

ch iv es p ro v id e nu m er ou s da ta w hi c h ca n b e co rr o b o ra te d by a c los e e x am in a t io n o f the se mo sa ics n s t u o r by p h o to g ra p h s ta ke n a fter th e w o rk w a s d o n e . T h e s a m e s itu a tio n ap p lie s to R a v e n n a . T h e re , m is s in g p a r ts i n a m o s a ic h a d b e e n fi lle d i n b y pa in tin g ( F ig. 9 ) b ut no w m os ai c s w e re b e in g u s ed ( 4 5 ). V e n ic e a ls o s u f-fe red th e sa m e f a te . M o st o f th es e re s to ra tio ns h ad n o ba sis in ic on o gra p h ic re se a rch a nd th eres ul ts s h o w i t . A c c o rd in g to a s y s te m o f p a y-m en t ca lcu la ted b y the s ur fac e ar ea , h un dr ed so f s q u ar e m e tre s w e re co m p le te ly re d o n e , th er e -b y d e s t r o y in g t h e o ld m o s a ic s . T h e s lo w a n d m

e tic u lo us w o rk o f in c o rp o ra tin g t h e o ld p a r tsth at ha d su rv iv e d in to th e ne w w or k w a s n o tpa id fo r a t a ll (4 6 ) .

In I ta ly w e fin d t h e s a m e m o s a ic is ts w o rk in g in m an y d iffer e n t p lac es . T h e s e 1 9t h c e n tu ry re -s to re rs w e re L ib o rio S a lan d ri , w o rk in g in R om e , at S t. M a rk 's in V e n ic e , an d at S t . A p ol lin a re N u ov o i n R a v e n n a ; F e lic e K ib e l, w h o w o r k e d a t S t. C o s ta n z a in R o m e a n d a t S t. A p o llin a re N u ov o , a fte r S al a n d ri; a nd G io v a n n i M o ro , w ho w o rk e d a t S t. M a r k 's , a t' Sa n M ic h e le in A fri-c isc o an d lat er at T o rc el lo (4 7 ). T he ir m e th od sre se m bl e e a c h ot h e r. Le t u s ta k e th e e x a m pl e w hic

h is be st kn ow n to m e pe rs on al ly. Gi ov an ni M oro , t he m os ai cis t w ho h ad le ar n-e d the c ra ft i n M ilan w ith R af fae lli , b eg an w o rkin S t. M a r k 's in 1 8 2 2 a n d s ta y e d u n t il 1 8 5 8 .In 1 84 5 , h is na m e is lin ke d wi th th e m o s a ic so f S a n M ic h e le A fr ic is c o . H e a ls o h a d th e r e -s p o ns ib ili t y o f re s t o r ing t h e m o s a ic s o n th e w e s t w a ll o f th e b a s ili c a in T o rc e llo , w h e re h e w o r ke d be tw e e n 1 8 5 2 a n d 18 56 . B r ief ly, w ekn o w b y ex am in a tio n n s t u a n d a rc h iv a l r e -s e a rc h t h a t M o ro re pl a c e d im p or tan t a re a s o fth e o r igi n a l m o s a ic a t T o rc el lo, u s in g tw o m e -th o d s : a ) b y c o m p le te ly re d o in g , a ft e r h is o w n de si g n , h e a vi ly d a m a g e d se ct ion s (s u c h a s the a rc h a n ge ls o f th e A n a s ta si s r e g is te r (F ig . 1 0 ) ; b ) b y c o p yi n g th e o r ig in a l m o s a ic s v er y c a r e -fu lly w ith n e w te s se ra e , f o llo w in g co lo u re d t ra c -in g s (4 7 a ). T h e co m m iss io n s o f th e A c a d e m y c f F in e Ar ts w h ich a pp ro ve d t hi s w or k h a d g iv en h im b y c o n t r a c t t he r igh t t o t a k e aw a y th e o ld c ub e s o f t he m o sa ic s h e h a d re p lac ed ( 4 8 ). Th us a rou nd 1 85 0 it w a s s till co ns id er ed no rm a lin of fic ial ci rcl e s to h a v e o ld m o s a ic s c o m p le te -ly r e m a d e w ith m o d e rn te s s e ra e . M o ro , a s h rew d c o n no is s e u r a n d ve ry g re e d y , a b u s e d t h is p r i- vil eg e by re m ov in g so m e h e ad s wh ic h we re ve ry w el l p r e s e r v e d a n d re pl ac in g t he m w ith

c o pie s . H e at ta ch ed t he o rig in al s t o a ne w s up p o rt a n d so ld th em s e c re tly . P u bli c o p ini o n w a s s h a ke n by t h is w h e n it c a m e to li g h t a fe w y e a rs la te r o n the o c c a s io n o f a n u n c o n n e c t-e d di s g ra c e w h ic h re m o ve d M o ro f ro m h is p o -

s it io n a s m o s ai c is t o f S t . M a rk ' s. A s a r e s ul t of al l th is , t od ay w e ha ve t he a d va nt ag e o fb e ing a ble to c om p a re t h e or igi na ls, w h ic h we re fou nd a nd pu t b a ck in pl ac e, wi th Mo ro 's co pie s, w h ic h h a v e a ls o b e e n p re s e rve d . F o r th e p rin -c ip a l h e a d s, M o ro p ro v id e d a ve ry ca re fu lly d o n e p ie ce o f w o r k , c o p ie d s t o n e b y s t o n e . T h e y c a n i n n o w a y b e c o m p a re d t o th e m o s a ic s th a t M or o e x e c ut e d f re eh a n d , s u ch a s t h e To rc el lo arc ha n ge ls cit ed , w h os e s ha p es w ere p ur po se ly c ha ng e d, it is sa id , s o th at M or oc o u ld ma ke m o n e y o n the g ol d b ac kg ro u n d (49 ).T he s to ry o f M o ro a t T o rc e llo i s i n te re st ing o nm o re t h a n o n e s c o re a nd s he ds l ig h t n o t o n ly o n th e m o s a ic is t b ut a lso o n t he a ut h o rit ies in ch a rg e o f t h e m o s a ic s . I t is o b v io u s th a t M o ro w a s n o t o v e r ly c o n s c ie n tio u s . I t is s a id t h a t, in a d e p o s itio n b y o n e o f h is fo rm e r a p p re n t ic e s , M o ro is a cc us e d o f s p r in k lin g th e m o s ai c s o f S t . M a rk 's w ith w a t e r i n th e w in te r s o th a t th e fr o s t w o ul d s p lit t h e m a nd h e w o u ld , c o n se -q u e nt ly, b e a s s u re d o f w o rk . H e w as a p oo rd ra u g h ts m a n - s e e th e T o rc e llo a rc h a n g e ls . H e w as , h o w e ve r, a c on no is se ur of be au tiful pie ce sa n d , b y n e c e ss ity , a fa s tid io u s c o p y ist . O n th e o th e r ha nd , t he c o m m iss io n o f the A ca de m y o fF ine A rt s h a d r es to ra tio n cr ite r ia w hi c h w er ea t th e v e r y le a s t d e b a ta b le , o r ra th e r , i t h a d o n ly v e ry v a g u e cr ite ria . T h e c o m m is s io n 's m o ra lr e s p on si b il ity se e m s m u ch m o re in vo lv e d in th is a u th o riz e d d e s tr u c tio n b y a c o n tr a c to r w h o , in

th is c a s e , w a s M o ro , b u t w h o c o u ld h av e b e e n a n o th e r m o s a ic is t w ith t h e s a m e a s c rib e d fa u lt s . T w e n ty y e a r s la t e r , in V e n e tia n c ir cl e s in t e r e s t e d in r e s t o r a t io n a r e a c t io n w a s t o b re a k o ut .

A fte r M o ro w a s f ire d , t h e s e a rc h fo r h is s u b s ti t u t e w e n t o n for s e v e r a l y e ar s u n t il t h e fir m of S a lv ia t i a n d C o m p a n y s u c c e s s fu lly b id fo r th e w o r k a n d w a s h ir ed . T h e f irm w o rk ed a t St . M a rk ' s fro m 1 8 7 6 t hr ou g h 1 8 8 0 a n d a t T or ce llo in 1 8 7 2 a nd 1 87 3 (5 0 ). Th e ex pe rie nc ew ith t h e S a lv ia t i fi rm w a s h a r d ly h a p p ie r t h a n w ith M o ro . In g e n e ra l, t h e S a lv ia ti s w o r k e d in a c a r e le s s w a y , u s in g g la s

s te ss e ra , e in lo u d c o lo u r s , c u t to o l a r g e , a n d s e t w ith o u t c a r e . E v e n in th e 1 8 6 0 s a n d 1 8 7 0 s , t h e s e m o s a ic is ts e n t ir e ly re p la c ed t h o ld , d e t er io r a te d d e c or a -tion s w ith n ew m o sa ics (a fte r ca rto on s, it's tr ue ).O ne o f t he m o st re ve al ing e xa m pl es o f th e irm e t h o d is p r ov id e d b y t he r o w o f A p o s t le s inth e L a st Ju d g m e n t, ag a in a t T o rc e llo . L o o k in g a t th e rig h t s ide o f t h is s e rie s , w h ich ,i s a lm o s te nt ire ly re d o ne , w e n o te t w o e s s e n tia l t h in g s :a) a ce rt a in s tyl ist ic fid eli ty in the c op ie s, m a in -ta ine d b y m ea ns o f d ra w in g s a nd c o lo ur ed tr a c -ing s m a d e fro m th e o ld m o s a ics t h a t t h e y d e -s tro y e d a n d ; b ) t h e c rud e in d u s tr ia l te c h n iqu e o f t h e c o n tr a c t o r 's w o r k . T h e c le a rl y v is ib les e a m s b e tw e e n s e c tio n s o f th e m o s a ic ind ic a te th a t th e S a lv ia tis p u t th e m o s a ic t o g et h e r in th e ir l ab or at or y a n d t he n at t ac h e d it, w he n itw a s fi n is h e d , to t h e w a ll . T he r e s u lts a r e m e -

3



di oc re . T he r o ws of te s se ra e d o n o t c o nt in ue co rre c tly , be ing un a lig ned at the jun ctu res .S o m et im e s e v en t he ma t eri a ls a re d iff e re n t if th e ti m e be twe e n th e c om ple tion of s eg m e n tsco r re sp o nd e d to t h e ru nn ing o u t o f th e s am e

s toc k.Th e T o rce llo m os aics an d th e ir r esto rat io n b y

th e S a lv ia tis w e re i n clu d ed in a n e x p lo siv e a r-gu m e n t in th e ea r ly 1 87 0 s o v er t he r es to ra tion s in St. M a rk's. Ag a ins t re s tor atio n, o n o n e s ide . wa s A lvis e Z orz i, a frie n d o f, R us kin and an intr ans ige n t d efen de r of arch aeo log ical exa cti-tud e . O n th e o the r sid e w as E ug ene Vio llet - le-D u c. In h is ar gum en t, Zo rzi c ited , am on g ot her s ,th e re s to r ati o n o f t h e m os aic s o f th e Z e no ch a pe l in S t. M ar k 's ( 5 1) . Vio llet- le -D u c re sp o nd -ed by s pe a ki n g h igh ly o f th e To rce llo re st o ra -ti o ns wh ich he h ad kn o wn de v is u (52 ). W e

kn ow n t he m d e v isu to o an d c a n j u dg e th e m forou rs el ve s ( 52 a ).W hil e Zo rzi in V en ice was in d ign ant ov e r

th e r e ne wa l of the ma rbl e s h ea t hin g o f S t .M ark 's, b efo re t h e S alv iatis be g an wo rk a t To r-ce llo, the m os aics of Sici ly, R om e an d R ave nna w er e be ing d ilig ent ly c o mp lete d. I n T ries te , t h em o sa ic s o f th e n o rth a ps e o f th e ch u rc h of S an Giu sto und erw ent a tr uly revo lut iona ry r esto ra-tio n . T h ey ha d na rro w ly m is s ed fal lin g into the h a nd s of M o ro w h o, in 1 8 56 , h a d pr op o se d re d o-ing the m, a nd of th e S alvi atis who , in 186 0, a lso wa n ted to rem a ke the m co mp lete ly. T hei r ac tual re st o re r, G io va n n i R ig h e tti , b u ilt a s u

pp o rti n gs ca ffol d ing ins id e th e a ps e w h ich co n for m e d to t h e m os aic sur fac e . T his wa s do ne to a vo idd am a g e to t he str u ct u re o f t h e m os a ic . Th e nhe r em o v ed t he su p po rt ing wa ll, b e gi nn in g w ithc a re fu l d e m o liti o n o n t h e e x te r ior o f t h e b uil d -in g , an d re join e d th e m o s ai cs f ro m t he ba c k.N ex t, h ie r em o v ed th e or ig in a l b e d of li m e ce -m ent , re p lac ing i t w ith P ort land ce m en t an d r e -bu ilt t h e w all , al l ac c or d ing to a m eth od t ha t he de scr ibes in det ail in a sm all boo k ( 53) .He d id this w or k in 1 86 6 . I n 18 7 7- 1 87 8 , th e sa me m e t ho d s w ere us ed in t h e r est o ra t ion of t heso u th a p se o f S an G iu s to ( 54 ) .

Ev en t ho u gh Rig he tt i s m e th od ha s im pe r-fec t ion s , t h ey are mi n im a l w h e n co m p a re d to wh a t w as b ein g d o ne ev e ryw he re e lse in It a ly. N ea r ly a c e ntu r y la te r, th e s a me me tho d w a sto b e u s ed by Fe rdin a nd o F o rla t i o n th e la rge m os aic sur fa ce s of the arc h es of S t. M ark 's (5 5).

In 1 877 , Z orz i pro po sed the cre ati on o f a com mi s sio n fo r th e co nse rva tion of S t. M ar k 's.Its m e m b e rs w o u ld b e a r tis t s a n d a rc h ae o lo -g is ts w h o w o u ld d ire c t th e w or k of a rc h ite c ts ,a r tis a ns a nd wo rkm e n . Th a nk s to the init iativ e o f a c er ta in P ell a nd a , th e m o sa ics rem o ve d fro mth e Z en o ch ape l ha d b e en sto red a wa y in pa c k-ing ca s es . Zo r zi p lea d ed th a t th ey s ho u ld be p ut b ack in plac e a nd o ppo sed th eir r ema kin g-re s to ra t io n by th e S al vi at i m et h od c u rr en t ly us ed. To sup por t hi s ar g um ent , Zo rzi c ite d th e o pi n ion of P ier o S a cc a rdo , an oth e r d e fe n de r of

th e ar ch a e olo g ic a l re st o ra tio n o f th e m o nu -me n t: if th e m o sa ic i s da m a g ed in s o m e pa rts, o ne mu st re do wi t h s c ru p ulo us r es t rai n t o n lyth o se p a rts wh ic h a re d am ag e d o r m is si n g a n dn ot t a ke ap a rt th e w ho le c om p os itio n in o rd e r

to m a k e it m o re b ea u tif u l a n d c om p le te (5 6 ). Th e co mm iss ion whi c h Z orz i pro po s ed was

s e t u p in 18 7 8 to o v er se e t he w o rk i n th e b a-s ilic a . O ne o f its m e m b e rs , S a cc a rd o , h a d th e res pon sib ility of o rga niz in g a sp eci a l m os a ics wor ksh op for the bas ilic a an d d raw ing up itsrule s .

A fte r th e S a lv ia tis le ft in 18 8 0, P ie t ro d eV e cc h is, f ro m R o m e , m a n ag e d th e w o rks h o p. H is w ork on the m o sa ics in th e s out h g a lle r yo f S t. M ark 's w a s ju dg e d u ns a tis fa ct o ry a nd hewa s d ism isse d in 18 83. Sac card o t hen him sel fas s um ed the dire cto rshi p of the wo rksh op

Sa c ca rd o e xp la in e d hi s p r inc iple s o f c o ns e r-v a ti on a n d re s to ra ti on i n hi s bo o k o n th e m o -s a ics of S t. M a rk 's c ite d a b ov e . H e p r ac ti se d p re v en tive co n se rv at io n a nd us e d a ll k ind s of wa ys to p re s erv e th e m os a ics (5 7 ). H e a lso def e nd ed the prin cip le - app lie d th an k G od, v er y ra r ely - o f r e mo vin g m o sa ics wh e n it is n ec e ss a ry to r e pa ir w a lls. F ar the r on , sp e ak in go f c a se s in wh ich t he mo s aic s h a ve be c om ed e ta c he d fr o m the w a ll, h e pr a ise d t h e u se o fco p pe r , b ron z e o r ir o n n a ils wh ic h p re v en t the mo sai c s f rom falli n g a nd a lso ex p lai n ed the me -th o d o f in jec t ing pu r e li q uid Po rtla nd c em en t be h ind the mo saic (58 ). F inal ly, w hile em pha siz-in g its lim itati o ns , he too k a sta n d f o r t h e c om -po s itio n o f mo sa ic s f rom the ba c k ( 5 9) .

T he re su lts of S ac c ar do 's w o rk a t St . M a rk 's in t he 1 89 0s a ppe are d p erio dica lly i n th e R e la zio n i su i re st a ur i e s e gu it i n e lla a s ilita di S an M ar c o d i Ve nez ia.

T he Re g ion al O ffic e fo r th e C o ns e rva tion of t he M on um ent s o f the Ve ne t o w as bein g o r-g a niz ed at t h is t ime als o. I ts d irec tor, F ed eric oB erc h et , su p er v ise d th e r e sto rat io n o f a gre a tnu m b e r o f m o nu m e nt s an d p ub lish e d th e ir re -s ults in the ann ual inst alm ent s of R ela z io ni de l l Uff icio Re g ion ale pe r la Co n se r va z ion e d e im o nu m en t i d e l V e ne t o.

II w a s B er c he t wh o w a s r e sp o ns ib le f or p utt -ing ba c k th e a uth en ti c T o rc e llo he a ds i n t h ei ro rigi na l pl ac e s in 1 89 6 -1 8 97 ( 6 0) . B e s id es r e-pla cing the he ads , the m osa icist s al so c ons oli-d ate d, w ith cem en t, th e te s se rae d eta che d fr o mthe m or tar b ed . W h ere pa int h ad bee n u sed toc ov e r g a ps in th e m o sa ic s , it w a s re m ov e d a nd ne w te s se rae w e re in s er te d. T he y al s o a n ch o re d the m o sa ics t o t h e w al l wi t h n a ils . R e ad ing repo rts from 18 96- 1 89 7 of the ope rati o n, a s w ella s c lose ly s tud y ing the res ults , m ake s ob vio usit s e n or m o u s d iffe r en c e in p r inc iple s a n d e x-e cuti on, des pite im per fec tion s, f r om wo rk o f.th e p as t (61 ).

In t h e 1 8 9 0 s t h e S alv iati n am e re a p pe a rs w hen a c erta in N ovo , w ho h ad bee n he ad of th eS al vi at i w o r ks h op s fo r tw e nt y ye a rs , w a s e n -

31



F ig . 1 2 - D a p h ni , b e m a. r c h a n g e l G a b r ie l, st a t e o f p re s e r v a tio n c . 1 8 8 0 -1 8 9 0

F ig . 13 - D a ph ni , b e m a. Ar c h a n g e l G ab rie l, c o n d itio n i n 19 7 6

g a ge d to r es to re t he m o s a ic s a t D a p h n i i nG re e c e ( 6 2 ) . I t w o u ld b e t e m p tin g , e v e n p o s -s ibl e , to im a gi n e N o v o a s a y o u n g m a n o n the s c a ffo ld in g s o f T o r c e ll o o r S t . M a rk s . T h e r e -s t o r a tio n a t D a ph n i, e v e n if i t i s h ig h ly c o n -tr o v er sia l tod a y . is ne v e r the le ss a

s te p f or w a rd w h e n c o m p a re d t o w o rk o f t w e n ty y e a rs e a rlie r. A ll th e m o s a ic s w e r e re m o v e d fro m t h e w a ll s a n d p u t b a c k in p la c e o n c e m e n t m o rt a r . O n ly m is s ing p ar ts w e re r em a de a nd th e fe w b ef ore p h o to g ra p h s w h ic h a llo w u s t o ju d g e th e o p e ra -tio n p ro ve it (F ig s . 12 -1 6) (6 3 ) . T h e m o s t fa m o u sr e m a ki n g is t h e c om p le te ly in ve n t e d h e ad o fC h ris t in th e D o u b tin g T h o m a s o n th e w e s t w a ll of th e so ut h a rm , fo llo w e d b y the r e m a d e h e a ds in th e T ra ns fig u ra tio n in th e n or th- w es t pe n-d e nt ive (F ig s. 1 4 -1 6 ). F in al ly, as a s u p ple m en ta ry op er at io n , N o v o h a d to un c o v e r th e m o s a ic s of the n ar th ex (T h e L ife o f t he V irg in ) h id de n un d er a la ye r o f w hi te w a s h . H e p ut th e m o n ne w a rc h ite ct u ra l su p p o rts t o r e p la c e t he o ld w a lls w h ic h w e re c ru m b lin g .

I f V io lle t- le - D uc h a d li k e d th e re s t o r a t io n s a t T o rc e ll o , G a b r ie l M il le t s a n g t h e p r a is e s o f t ho s e of D a p h ni . I t i s t ru e th a t t h e d is ta n c e s ep a r a t in g t h e t w o p r o je c t s is in c a lc u la b le . A tT or ce llo th e S a lv ia tis d e s tro ye d th e old m o sa ic s a nd r em a d e t he m a cc o rd ing t o c a r to o n s (6 4 ) .A t D a ph n i, th e o ld m o s a ic s w er e pr es e r ve d ,

the ir ce m en t b e d ren e w e d , a nd o nl y t h o se p ar tsw h ic h n o l o n g e r e x is te d w e re in v e n te d in th e B yz a n tin e m a nn e r . C u riou s ly, N ov o 's s ty le in -clu d e s a c h e ck er bo ar d m o tif w h ich h e us e d f or c e rta in g o ld an d si lv e r su rf ac e s, su c h a s th e

c ro s s e d n im b us e s o f C h ri s t in th e B a p tis m an d in t h e T ra n s fig u ra tio n . It r e c a lls a s im ila r m o tif o bs e rv e d b y Bo v in i in t h e w o r k o f K ib el (6 5 ) .S im ila rly , th e im pr o p er a nd o ut -o f-p la ce u se o ftr an sp ar en t g re e n a n d y e llo w tes s era e at D el ph ile a d s o n e t o t hi nk t h a t N o vo h a d s e en t h e se c o lo ur s in th e o rig in al m os a ic s . T h e y w e re a b u n -d a n t ly u s e d in t h e o r ig in a l T o r c e llo w o r k s h o p an d he m a y h a ve im a gi ne d he w a s w or kin g in th e ol d m an n e r " b y w or kin g a cc or di ng t o h is o b s e rv a tio n s . T h e d e s ig n o f th e r e m a d e s e c tio n s s h o w s th a t N o v o v e ry c lo s e ly c o p ie d th e s ty le o f th e w or ks h o p w h os e w o r k h e w ish e d t o c o m p le te .

T h e la s t e xa m pl e I w o u ld li ke to p re se n t, tob r ing t h is d is cu s s io n to t h e th re s ho ld o f c o n -te m p o ra ry t im e s , c o n c e rn s t h e m o s a ic s o f th e m a in a p s e o f T o rce llo w h ic h h a d t o b e re s tor e d in 19 19 ( 66 ). Be ca u se e n ti re ro w s o f s to ne w e re e ro d e d a n d m a n y m o s a ic s w e r e m is s in g , t h e C o o p er at iv e M o s a ic is ti d i V e n ez ia w h ich w a s d o in g th e w o rk p ro p o se d to th e S o p rin te n d en z a a i M o nu m en ti th at th e en tir e m o s ai c b e re m ov -e d f ro m t h e w a ll a n d re d o n e in t h e la b o ra to ry .

3 2



Figs. 14-15 - Daphni, nave. he Transfiguration, state of preservation c. 1880 - 1890

Fig. 16 - Daphni, nave. he Transfiguration, condition in 1976

33



T h e F in e A rt s s e c tio n o f t h e M in is try o f P u b lic In s t r u c ti o n d e c id e d , h o w e v e r , t h a t t h e w o r k s h o u ld b e d o n e in s i tu w it h t h e r e m o v a l o f o n ly c e rt a in p ar ts o f th e d e c or a tio n , o f t h e g ol dg ro u n d a n d o f th e v e g e ta tio n .

D u r in g w o r k in t h e h e m ic y c le o f t h e a p s e , th e m o s a ic is ts fo u n d a n 1 8 th c e n tu ry r e st o ra -tion in a n im po rta n t p a r t o f th e r o w o f A p o s tle s .T h e S o p rint e nd e n za a s k ed th e M in is try - th o u gh e x p re s s in g d o u b t - w h e th e r i t w a s n e c e s s a ry to re m o ve th e re s to re d m o s a ic a n d re m a k e it c o m -p le te ly . A c o m m is s io n o f th e S u p e r io r C o u n c il fo r A nt iq u it ie s a n d F in e A r ts w en t t o th e s it e a nd d e c id e d t o r et a in t h e o ld r e st o ra t io n b e -c a u s e : "if o n e w e re to r e m o v e a ll t h e m o s a ic s fo r m e r ly r e s t o r e d , it w o u ld e ffe c t a g r e a t p a r to f th e d e c o r a te d s u r fa c e .

T o d a y , th e lis t o f m o s a ic s o n w h ic h w o rk is b e in g , o

r h a s b e e n , c a r r ie d o u t c o m p r is e s a ll th e m o n u m e n t s k n o w n t o u s . W h e t h e r It is

c le a n in g , m a in te n a n c e o r c o n s e rv a tio n , s a lv a g e o f e n d a n g e re d p a r ts , o r p ro te c tio n a g a in s t t h e p o s s ib le e ffe ct s o f t w o w o rld w ar s , t h e pr o bl e m sra is e d h e lp u s to k n o w th e s e m o sa ic s b e tte r a n dc on s e q u e n tly to s tu d y th e m b e tte r. T h e d is co v -e rie s f o r t h e a r t h is to ria n d u rin g t h e l a s t d e c a d e s ar e in n u m e ra b le . H e s tar ts f ro m a fa r m o re s o lid d o c u m e n ta ry b a s e in h is s tu d ie s b e fo re s k e tc h -in g o u t h is s y n t h e s e s . T h e m o d e r n s t u d y o f m o s a ic s b e g in s w ith a c h a p te r o f p u re a rc h a e o -lo g y w h ic h a lo n e c a n s p a re th e a rt h is to r ia n a m a s s o f u se le s s s p e c u la tio n.

Th e p ro b le m s r a is ed to da y b y t h e r e st or a tio n o f m o s a ic s re m a in v e ry c o m p le x , es p e ci a lly o n t h e te c h n ic a l l e v e l. l f e e l c e r t a in t h a t w e w ill le a r n t h e ir c u r r e n t a s p e c ts h e r e . M y a rt h is -t o r ic a l r e m a r k s s to p h e r e a s l tu r n o v e r t h e fl o o r t o th e r e s t o r e r s .

T h e d is c u s s io n w h ic h fo llo w e d th is l e c t u r e w ill b e fo u n d o n p a g e 3 7 .

No te s

1 . E . G e rs p a c h , La M o sa iq u e, P a r is , n . d . In t h e s a m e c a t e g o ry b u t o f le s s in te r e s t: G . R io lo , D e ll'a rt ificio p ra tic o d e i m o s a ic i a n tic h i e m o d e rn i, P a le rm o , 1 8 7 0 ;A . A g a z zi , / / m o s ai c o in I ta lia , M ila n , 1 9 2 6 .

2 . P . S a c c a rd o , Le s M os a iq u e s de S a in t-M a rc a V e n is e ,V e ni ce , 1 8 96 .

3 . T h e f o ll o w in g w o r k s h a v e g o o d g e n e ra lb ib lio g r a -p h ie s : H . P . L 'O r a n g e a n d P . J . N o r d h a g e n , M o s ai k

v o n d e r A n t ik e b is z u m M it te la lt e r M un ic h, 1 96 0 ;G. B o v in i, S a g g io d i b ib lio g ra fia s u R a v e nn a a nt ic s , B o lo gn a , 1 9 68 , es p ec ia lly X IV , 5 , R es ta u r o a i m o -s a ic i , p . 7 6 . S e e a ls o n o t e 4 .

4 . S o m e o f th e b e t t e r k n o w n t it le s a r e : I . C ia m p in i, V e te ra m o ni m en ta in q u ib u s p ra ec ip ue m u s iva o p er as a cr a ru m p ro fa n a ru m q u e a ed iu m s tr u c tu ra , 2 vo l. ,R om e , 1 9 60 -1 9 69 ; G . B . d e R o ss i, M o s ai ci cr is tia n ie s a g g i d i p a vi m en ti d e lle ch ie s e d i R om a a n te rio ri a l s e c . X V R o m e, 1 87 3 -1 89 9 ; J . W ilp e r t , D ie ro m i-s c h e n M o s a ik e n u n d M a le re ie n d e r k irc h lic h e n B a u te n v o n I V b is X lll J a h r h u n d e r t 4 v ol. , F re ib u rg , 1 9 6 1 ;C . R . M o re y , L o s t M o s a ic s a n d F re s c o e s o f th e M idd le P e rio d , P r in c e t o n , 1 9 1 5 ; A . V e n t u r i, M os a ici

c r ist ia n i d i R o m a R o m e , 1 9 2 5 ; G . M a t t h ia e , ec h ie s e d i R o m a d a l I V a l X s e c o lo R o m e 1 9 6 2 ;P . J . N o r d h a g e n , '' T h e M o s a ic s o f J o h n V II , A c ta In s titu ti R o m a n i N o rv e g ia e , 2 , R o m e , 1 9 6 5 ; S . W a e t-z o ld t, D ie K o p p ie n d e s 1 7 J a h rh u n d e r ts n a c h M o -s a ik e n u n d W a n d m a ler e ien in R o m , V ie n n a , 1 9 6 4 ; W . O a k e s h o tt, T h e M o s ai c s o f R o m e fro m th e T h ird to th e F o u r te e n th C e n tu r ie s , L o n d o n , 1 9 6 7 , w it h a b ib li o g ra p h y ; G . M a t th ia e , M o s a ic i m e d io ev a li d e lle ch ie s e d i R o m a , 2 vo l. , R o m e, 1 96 7 . T h is la s t w o rk co n ta in s ex ce ll en t ph o to gr ap h s ta ke n o n th e sa m ele v e l a s th e m os ai cs , tec h ni c a l n o tes o n th e co n di t io no f th e m o sa ic s , t h e r es u lts o f ex te n si ve r es e ar c h in a r c h iv es , as w e ll as a d e t a ile d bi bl io gr ap h y.

4 a . T h e m o s t c o m p le t e re c o r d o f r e s t o r a ti o n s i n S ic ily a re f ou n d in : O

. D e m u s , T h e M o s a ic s o f N o rm a n S ic ily , Lon d o n , 1 9 4 9 , p p . 1 0 - 1 1 , 2 9 - 3 6, 7 7 - 7 8, 1 08 -1 1 2 . F o r a re ce n t a n al ys is o f t he m o s ai cs r e s to re d in th e P a la ti n e C h a p e l, s e e I. B e c k , T h e F irs tM o s a ic s o f t h e C a p p el la P al a t ina i n Pa le rm o , B yz a n -t io n , 4 0 , 1 9 7 9 , p p . 1 1 9 - 1 6 4 .

5 . W e h a ve n e ar ly c om p le te s ch o la rly d o cu m en ta ti on fo r m o st of th e m a jo r B y za n tin e m o nu m e nt s of th is p e ri od t ha n ks t o th e D um b a rt on O a k s C en te r fo rB y z an t in e S t u d ie s w h ic h , w it h a g ra n t f ro m t h e N a tio n al E nd o w m e n t fo r t h e H u m an it ie s . o r g a n iz ed o n- si t e re s e a rc h a n d p h o t o g ra p h y in t he V e n e t o , in G re e c e ( D a p h n i a n d H o s io s L o u k a s ) , a n d in T u r k e y ( Is ta n b u l, S t . S o p h ia ) . A m o n g c h u r c h e s , o n ly N e a

M o n i in C h io s ha s n o t y e t b e e n s y s te m a tic a lly p h ot og ra p h e d a n d st ud ie d . S m a ll e r m o sa ic s c a n b e fo u n d i n s i tu in M o u n t A t h o s ( N . K o n d a k o v ,P a m ia tn ik i C h r is t ia n s k a g o ls s k u s tv a n a A to n e , S t.P e te rs b u r g , 1 90 2 ) o r d et ac h ed f ro m t h e ir o rig in a ls up p or ts . F o r a de t ai led lis t o f w al l m o s ai cs , se e V . G las b e rg , R ep e rto ire de l a m os ai qu e m e di ev a lepa riet al e e t po r ta tiv e, A m st er da m , 1 9 7 4 .

6. T . W h itte m o re , Th e M o sa ic s o f St . S o ph ia a t Ist an b ul ,B o s to n , 1 9 4 2 , 3 r d p a r t , p p . 9 - 2 0 (t h e Z o e p a n e l).

7 . E . D ie z - O . D e m u s, B y za n tin e M o s a ic s in G re e c e . D ap h n i an d H os io s Lo u ka s, C a m b ridg e , 1 93 1 .

8 . V . La z ar ev , M o z a iki S o fii K iev s k o j, M os c ow , 19 6 0; H . L o gv in , K e iv 's H a g ia S o ph ia , K ie v , 1 9 7 1 .

9 . A . O rla n d o s , M o n u m e n ts b y za n tin s de C h io s , A the n s, 19 3 1, v o l. I I ; G . M a tth ia e , / m o s a ic i d e lla N e a M o n i a C h io s, R o m e, 19 6 4.

1 0 . O . D e m u s , D ie M o s ai k e n vo n S . M a rco in V e n e d ig ,B a d e n , V ie n n a , 1 9 3 5 .

1 1 . T he l a te s t a n a ly s is, w ith b ib lio g ra p h y, is I . A n d re e sc u , T o r c e llo I, T h e U n kn o w n C h r ist ; I I. A n a s t a s is a n d

La st Ju d g m e nt : T ru e H e a ds , F a ls e H e a d s ", D u m b ar to n O a k s P a pe rs (h e n c e fo r th a b b re v ia t e d a s D O P ) 26 ,1 9 7 2 , p p . 1 8 3 - 2 2 3 : id e m , T o rc e llo II I . T h e R e la t ive C h r o n o lo g y o f t h e W a ll M o sa ic s , D O P , 3 0 , 1 9 7 6 , p p . 2 4 5 - 3 3 5 .

1 2 . G . G e ro la , II m o s a ic o a b s id a le d e lla U r s ia n a , F el ixR av en n a, 5 , 1 9 1 2 , pp . 1 7 7 - 1 9 0 ; C . R ic ci , M o n u m e n ti: T a v o le s to ric h e d e i M o sa ic i d i R a v e n n a , LX X IV -L X X V,B a sil ica U rsia n a, fa s c . V I II , 4 , R o m e , 1 9 3 7 .

1 3 . V . L a z a r e v , M iha jlov s k ie M o z a ik i, M os c o w , '1 9 6 6 ; id e m , I m o s a ic i d e lla c h ie s a d e ll 'A r c a n g e lo M i-c h e le , F .R ., 3 rd s er ie s, 47 , 19 6 8, pp . 10 3 - 14 4 .

3 4



14 . M. Cam pit elli, N ote sul mo sa ico c on i d odici ap o-stoli d i S . Giu sto a Trieste , A rte Veneta, 12 , 19 58,p p. 19 - 30 ; M. Mirab ella Rober ti, San Giusto, Trie-

st e , 1970.

15. T he mosa ic s were p ublished b y G. Mi ll et in e

mo n astère d e Daphni. H istoire a rchitectu re mo-

saique , Paris , 1 899. Th e d ifferen ces betwe en thetwo mai n groups a p peared a ft er invest ig ation fro m scaf folding in D ecember 1 976.

16. See note 4 above, p p. 21 - 40 (the pane l of John I I C omnenus) .

1 7. S ee note 1 3 above.

18. See n ote 8 abov e.

1 9.

in Mura n o and àhn liche vene zi anische B a uten, Be rlin ,

In the las t style at T o rcello, se e note 11 a bove, an din the m osaic of M urano, H . Rathgen s , San Dona to

1 903.

2 0. 0. Demus , T he Mosaic s o f Norm an Sicily, Lo ndon,19 4 9; E. Kit zi nger, The Mo saics of Mo nrea le, Pa

lerm o, 1 960.

21. P. Unde r wood, T h e Evidenc e of Resto ration in t h eS anc tuary Mos aics o f the Chur ch o f the D orm itionat Nic a ea , DOP, 13 , 19 59, pp. 235 - 243.

22 . La test rese a rch and b ibliograph y in R. C o rmack,Nint h Cen tury Monu men tal Pa intin g and Mos aic in T hes salonik i, Lon don, 1968 , thesis ma n uscript.

23. C. Ma gno and E. H awkin s, T he A pse M osai cs o fSt. So p hia at Ist an bul. Rep o rt on Fie ld work ca rri edo ut in 1964 , DOP, 1 9, 1965, pp . 113 - 15 1 .

24. See n ote 4 abo ve.

25. G . Bovi n i, L'aspe t to primitiv o del mosa ico teodor i-riciano

raff igurantela 'C ivit as Clas is' in S. Apollin are

Nu ovo", F.R ., 5 5, 1951, p p. 57 - 62 , ill. ; id em , "Os -

serv azio ni sul fron tone del Pala ti um di Teod orico figurato n e l mosaico di S. Apoll inare Nuov o di Ra-ve nna", Fes tschrift fa r R. Egge r Klagenfu r t, 1952,pp. 9 6 - 99.

26. 0. D emu s mad e th is hyp othe sis in a pu blic le ctur eat Dum barton Oa ks in M ay, 1977.

27 . See n ote 11 ab ove.

28 . T his la st, k nown sinc e 14 82 fo r ha ving r esto redmo s aics, ca n be foun d under th e name o f PietroZorz i in the re c ords of th e Pro cu ratoria. See Sac -cardo, o p. cit., es pe cially pp . 3 8 - 39.

29 . b id.

30 . Ib id., pp . 87 , 219 - 2 20 .

Archiv io d i Stato , Pr ocurato ria d i San Marc o , Venice,1.

su pra A ct . vol. 17, p . 93, cf. F. On gan ia, Doc ume ntiper la sto ria d ell Au gust a Duc ale Ba silica di S anMar co di Vene z ia, V e nice, 188 6 , p. 91; S a ccardo,op. cit ., pp. 8 7, 20 6.

32. In 784, H a drian I au thorized C h arlemagn e to remov e pal a tii R avenn ate C ivitatis mos ivo a tque marm ores

cete ris que ex em plis tam in strato, quam q ue inpar ietibus siti s , cf. Ph. Jaffe , "Monume n ta carolin a ",Biblio te ca Reru m Germa nica rum, 4, Ber li n, 1867,reprin te d Aalen, 19 64, p. 2 68 . and G. Bovin i. Antichiri facimen ti n ei mosa ic i di S an Apo llinare Nuo v o di

R avenna," C orsi di cultura su ll arte rave nnate ebiza ntina, 196 6, p. 75.

33. Cf. Sime onis Magis tri, A nnale s , Corpu s Scriptoru m Histor iae Byzan tine, B onn , 1838 , 69 1, p. 1 2; G eorgiiM onach i, Vitae R ecentioru m Impera to rum , ib id.,843. 13. Se e als o C. M ang o, The Art o f the Byz a ntineE mpire, 31 2 -1453, En glewo od C liffs, 1 972 , p. 18 11.

33a. Cf . Micha eli s Pselli , S c ripta Mino ra, ed. E. Kur tz -F. D rexl, Milan , 1936, 299 in N. Oiko nomides, " SomeRema rks on the Imperial M osaics of Saint Sop h ia,a lecture gi v en at Dum barton Oa ks Center in 1975.

34. B ib. Na z. M arcian a, C ron. M agno, Par t. 5, It. Cl. 7,Cod. 517 , c67t, cf. O nga nia, op . cit. p. 1 1.

35. For th e b ackgrou nd of this p rob lem, wi th b ibliogra ph y,s ee C. Ce cc helli, A propo sito dell'ab sid e Latera-ne nse," Misc e llanea Bib liothecae H erzianae, Mu ni ch,1961 , pp. 13 - 1 8.

36. C. B ertelli, U n a ntico re st auro ne i m osaici di St a.M aria Maggi ore, Pa ragone , 1 9 55, pp. 40 - 42.

37. Se e n ote 12 a b ove.

38 D ie Frieden s kirche b ei Sansso u ci: Ein RO c kblick au fdie ersten 5 0 Jahre ih res Beste hens 1848 -1898Pots dam, 1898; L. Te sti, Storia della pittu ra venezian a,Berga mo, 1909, pp. 57, 64, 81.

3 9. S ee t he bib ligra phy i ndica ted in G. Bov ini, Saggio, pp. 56 - 57.

40 . Andre e scu, "Tor c ello III", p p . 261 - 26 4 and App en dixAl, p. 2 7 7.

41. Sa ccardo , Les mos aiq ues, p. 106.

42 . In fact, this meth od was st ill occasio nally used inthe 19t h century , a s in the m osaics in the va ul to f the south chapel — Saint C le ment (Le gend ofSain t Ma rk) — by P ietro d e Ve cchis, see below, p. 28.

43 . O. Pow st enko, "Th e Cathedr al of St. So p hia in Kie v ",in T he Ann als of the Ukr ainian Aca demy o f A rts and Sc ien ces in the U.S., 111 -1 V, 1954, p p. 18 - 20.

44. M ang o, M ater ials fo r the Stud y of the M osa ics ofSt. So p hia at Is ta nbul , D umbart on Oaks S tud ies, 8,

Washingto n, 1962.45 . Bo vini, Prin c ipali resta uri compiu ti nel seco lo scor-

so da Felice K ib el nei mos a ici di S . Apolli nare Nuovo di Ra ve nna", C CA RB, 196 6, pp. 8 3 - 104.

46. M atthiae, M osa ici me dioe vali, e spec ially t he ch apter "N ote tecnic h e," pp. 39 7 - 400.

4 7. Bovini , Principa li restauri ; Matthiae , ibid ., p. 402;F. De iche mann, Ra venn a, Ha upsta dt de s sp5 tantik eAbendland e s, Il Kom men tar, 2n d p art, Wie sb aden,19 7 6, pp. 38 - 3 9; Sacca rd o, Les mosa iq ues, pp. 234,240.

47a . Th e curi ous Archa nge l Gabr iel, as we see it toda yin Moro's r es toration , h is feet t ra mpling t he dragon

wh ile his lan ce pie rce s its ta il, could h av e been influe nc ed by t he Archan ge l Micha el of Potsd am -Mur an o. It is no t impos sib le to immagin e th t itwa s Moro wh o remo ved the Mu ra no mos aic around 1 839 . He w ou ld thus ha ve be en able to us e hisnewly- a cquired ic onograph ical knowl e dge when hedesig ned the A rch angel G ab riel of Tor cello a bou t1 853.

48. An dr eescu, "T o rcello I - II" , pp. 208 - 209.

49. Ide m , "Torcello Ill," p. 270 and Appe ndix A5, p p . 289-294.

5 0. Ib id., pp . 271 - 273 a nd Append ix A8, pp. 2 99 - 302;Sa ccar do, op . cit., pp. 184 - 1 85, 204 - 20 5.

51 . A . Zorzi , Os serva zion i into rno a i resta uri i nterni edest e rni della B asilica d i San Mar c o V enice , 187 7,expec ially pp. 1 21 -133; for an an a lysis of th e prevailin g a ttitude at that time, se e S. B oscarino, Il primointe rve nto del la S.P.A.B . a ll'estero . I l proble ma deirest au ri della B a silica di S a n Marco, " P sic on, 10 , 1977.

5



5 2. E . V io lle t - le - D u c , D e la r e s t a u r a t io n d e s a n c ie n s e d ific e s e n I ta lie , E n c y c lo p e d ie d A rc h ite c tu re , 2 n d s e r ie s , 1 , 1 8 7 2 , a f t e r w a r d s c it e d b y A . Z o r z i ( s e e n o t e 5 1 a b o ve ) w h o r e p ro d u c e d i t in it s e n ti re t y .S e e e s p e c ia lly p . 1 6 3 i n t h e Z o rz i r e fe re n c e .

5 2a . F o r t h o se p a rt s b e li e v e d to h a v e b e e n re s to r e d b y S a lv ia t i, s e e A n d re e s c u , T o r c e llo I II , p p . 2 7 1 - 2 7 2 , w it h il lu s tr a ti o n s .

5 3 . G . R ig h e tt i, S u g li a n ti c h i m o s a ic i d e lla c a t te d r a le d i S . G iu s t o e p a r t ic o la r m e n te s u i lo r o r e s t a u r i T rie s te , 1 8 6 6 .

5 4 . A r c h iv io S o p r in t e n d e n z a a i M o n u m e n t i T r ie s t e , A t ti S . G iu s to , M o s a ic i, R ife r ta in t o rn o a l la v o r o d i c o n s o lid a m e n t o e s e q u it o d a l C ivi c o U ffi c io d e lle P u b b lic h e C o s t r u z io n i a l m o s a ic o d e ll ' a lt a r e d i S a n G iu s to .

5 5 . F . F o r la ti , T h e W o r k o f R e s to r at io n in S a n M a r co in D e m u s , T h e C h u rc h o f S a n M a rc o in V e n ic e , D O S ,6 , W a s h in g to n , 1 9 6 0 , p p . 1 9 3 - 2 0 0 , e s p e c ia lly p p . 1 9 8 -1 9 9 ; ld e m L a B a s ilic a d i S a n M a r c o a tt r a v e r s o i s u o i r e s t a u ri T rie s te , 1 9 7 5 , p a s s im .

5 6 . S a c c a r d o , r e p o r t r e a d a t t h e A t e n e o V e n e t o , J u ly 2 7 , 1 8 6 4 , c it e d in Z o r z i, o p . c it. p . 1 4 4 .

5 7 . S a cc a rd o , L e s m o s a iq u e s , p . 1 2 7 .58 Ib id . , p . 1 7 8 .

5 9 Ib id . p p . 1 8 2 - 1 8 3 .

6 0 . Ill a R e la z io n e a n n u a le ( 1 8 9 5 ) d e ll'U ff ic io r e g io n a le p e r la c o n s e r v a z io n e d e i mo n u m e n t s d e l V e n e t o , V e n ic e , 1 8 9 6 , p p . 1 8 6 - 1 8 7 ; I V a R e la z io n e ( 1 8 9 6 , 1 8 9 7 , 1 8 9 8 ) , V e n ic e , 1 8 9 9 , p . 1 3 9 .

6 1. A n d re e s c u , T o rc e llo III , A p p e n d ix A 1 0 , p p . 3 0 6 -3 1 2 . 6 2 . G . M ille t, L e m o na s t er e d e D a ph in i X - XI. 6 3 . .P h o to g ra p h ie s a l'E c o le P ra tiq u e d e s H a u te s E tu d e s ,

V e S e c t io n , C a t a lo g u e d e s n e g a t if s d e l a C o lle c t io n c h r e t ie n n e e t b y z a n t in e f o n d e e p a r G a b r ie l M il le t , n e w e d it io n , P a r is , 1 9 5 5 , p p . 9 5 - 9 7 ; D ie z - D e m u s , B y z a n tin e M o s a ic s fig s . 66 , 6 7 , 8 4 - 8 7 , 8 9 , 9 0 , 9 8 , 1 0 3 .

6 4 . A n d y e t t h e s e p r a c t ic e s h a d b e e n s y s te m a t ic a lly c o n d e m n e d s in c e 1 85 9 , c f. A n d re e s c u , T o r c e llo I II , A p p e n d ix B , p p . 3 3 9 - 3 4 1 .

6 5 . S e e n o te 4 5 a b o v e .

6 6 . A n d re e s cu , ib id . , p p . 2 7 4 - 2 7 5 a n d A p p e n d ix A l2 ,p p. 3 1 4 - 3 38 .

6



D ISC US SI O N

T h e s e n o t es do n o t a tt e m p t t o r ep ro d uc ew or d f o r w o rd th e m a n y c o m m e n ts a n d q u e s -ti o ns . W e ha ve , h o w ev e r, tri e d to r ec or d t h ees se n tia l p o in ts, thu s s ho w in g t

h e ge n er a l d ire c-t io n o f th e d is c u s si o n w h ich fo llo w e d t h e l ec -tu res of M . La va g n e a nd of M m e . A n d ree sc u .

S iq. U rba ni: It w ou ld be in tere st ing to kn o w th e t e c h ni q ue M m e . A nd re e sc u u se s t o d ist in-g u is h th e res tor ed pa rts of a mo sa ic. Is the res o m e te c h n ic a l d oc u m en ta tion o f th e p ro b le m o f th e d ivi s io n b etw ee n o ld an d n ew s e ct ion s -o r a re t he re m e th o ds su c h a s ph o to gr a m m e try ,o r p h o t og ra p hs m ad e u nd er sp ec ial l ig h tin g, c h e m ica l a n a ly s e s, e tc .?

Mm e . A n dr ee scu : M a n y thi n gs c a n be de -te rm in e d o n t h e s c a ffo ld in g b y a s im p le , m e ti-c ulo us , a rch ae ol o gi ca l ex am in ati on wi th t he na k ed e ye, bu t t h is su bje ct, w itho ut qu es tion ,s h o u ld b e m u c h m o re d is c u ss e d .

M . B a s s ie r : I n m y p r e se nt st u d ie s , I h a v em ad e c on tac t w ith th e lab ora to ry o f p hy sic san d o pt ics at Be sa n co n. Th at o rg an iza tion h a sd e ve lo p e d a m e th o d of ha nd w r itin g a na lys is ba se d o n o p tic al c o m p a ris on s . B y s hi n in g a las e rbe am th rou gh the h o lo g ra m o f a do cu m e n t u si n gFo ur ier 's s er ies th ey ge t a n e xa ct gh os t oft h e ha nd wr itin g . T h a n k s t o t his p r oc es s , it is p os s ib le to d is ting ui s h b e tw e en th e t rue ha nd an d th e c o u n

te r fe it. If w e c o ns ide r t h e s p a ce s b e tw ee n te s s er a e

a s w ri ti n g , t h is m e th o d o f o p t ic a l c o m p a ri s on c an b e a pp lie d to th ei r c o m po siti on wh ic h is the ex p re ss ion of an ind iv id u a l t e ch ni q ue . W ith th is m e tho d, we h o pe to be a b le to ob jec tiv e ly def ine th e d iff ere nt te chn iq ue s, t he di f fer en tw a y s of l ay in g o u t o r se t ting th e te s s er a e , th e w o r k o f t his m os a ic ist or of tha t s tud io . If we a dd to th e in fo rm a tio n o bt a in e d b y o p tica l c o m -p a ris on th e a na lys is o f t h e m a te r ial ma ki n g u p th e t es s e rae a n d the jo in ts , t h e c o m p a ri s on o fth ei r p roc e s s o f a lter a tio n b y tim e a nd th e e le-

m en ts, t h e ir d a ting b y th e rm o lum in e sc en o e or by ot h e r m e a n s - w h e n d at in g is p o s si b le an d s ig n if ica nt - w e h a v e su ffic ie n t fac ts to dif -fer e n ti a te t h e o r ig in al p a r ts of a m o s a ic f r om a nc ien t o r re ce nt res tor a tio ns .

S ig . U rb a n i: T h e n th e o r ig in a l fo rm o f ea c h e le m e nt c o u ld be fo un d b y c o m p a ri n g it t o a s e rie s o f s ta n da rd s ?

M r. N o v is : W e m u s t b e v er y c ar e fu l to di s -tin gu is h t h e w o rk o f o n e m a n f ro m t h a t o fa no the r. M an y p eo ple co uld ha ve be en em plo yed o n the bi g m os aic s, the m ain su bje cts do ne by the m as ter an d t h e bo rde rs by his he lpe rs .

M m e . A n d ree sc u : S o m e tim e s it is p o s s ib leto d is t in g u is h di ff ir e n t h a n d s w o r k in g i n t h e s a m e s t u d io . A g o o d e x a m p le o f t h is i s th e

(m os a ic of the La st J ud ge m e nt a t T or c el lo. T he re t h e a u th en t ic p a r ts in t h e ro w o f A p o s tl es , o n the le ft s id e , h a v e b e en d o ne , a t le a s t in r e g ar d to the fe et an d t h e gre en ba ck gro un d, by tw oha nd s. F r o m fa r a w a y y o u c a n ' t t e ll t he d if -fe r en c e bu t i t 's v e r y c le a r c lo s e up . T he d if -fe re n ce s sh o w th a t th e s u rfa c e to b e d e co ra te d ha d b een d ivid ed be twe en tw o m en of th e s am ete a m w h o h a d re c e iv e d v e ry s im ila r tr a in in g .

T o r e tu rn t o S ig . U rb a n i's q ue st io n , I w o u ld sa y th a t w e c an se e th e d if fe re n c e s b e t w e e n th e o ri g in al an d r es t or e d pa rts o f a m o sa ic b u t i t is no t e a sy to ex pre ss th e m in -a d e s cr ip-tive a n d n a rr at iv e w a y . I w o u ld l ik e t o s h o w y o u th e q ue sti onn air e u se d f or the sy ste ma tic an a-ly s is o f a m os a ic . A ce r ta in n um be r o f e lem en tsa re e x a m in e d , - t ec h n iq u e , c o lo u rs , m a te ri a ls ,p a rt s o f th e b o d ie s , e tc . If

t h e e x a m in at io n is m a d e a c c o rd ing to th is m e th o d , w e c a n e a s ily id en tify re pe titio ns , a nd thu s see w he the r t h ewo rk wa s d on e b y o ne s tu d io o nl y , o r w he th e roth er stu dio s o r m em be rs of a n o th e r tea m h av ec o lla b o r a te d o n it . W e ha v e be g u n th is in th e Ve ne to an d w e ha ve be en a ble to te st it i nG re e c e a n d a t S t. S o p hi a . T h e C en ter f o r B yz a n -tin e S tu d ie s c a n fur nis h d oc um en tat ion on th issu b je ct.

A t S t . S o p h ia , in Is t an b u l, al th o u g h o n ly a fe w m e t re s se p a r at e t h e m o sa ic o f Z o e f ro m th at of Jo hn 11 yo u c a n t e ll w it h o u t a d o u b t

th a t th e t e ch niq ue s a re dif fer e n t. T h e fir s t w as m a d e b e tw e e n 1 0 2 5 a n d 1 0 4 5 a n d t h e o t he r b e tw e e n 11 1 8 an d 1 1 22 . T h e c o lo ur s a n d t h e tex tur es of the v itre ou s p as tes we re cr u d e r i nth e se c on d p er iod .

37



S ig . U rb a n i: T h e q u a lity o f t h e m a te r ia l th e n c a n g iv e u s u s e fu l c lu e s ?

M m e . A n d re e s c u : T h e s h a p e s o f th e m a te -ria ls, t he ir th ic k ne s s , th e ir d im e n s io n s . e tc. , lik e th e p a le tt e u s e d , a re im p o rta n t p o in ts

w h ic h c a n b e a s s o c ia te d w ith c e r ta in p e rio d s a n d n o t w ith o t h e r s . F o r e x a m p le , e x a m in in g o n o n e h a n d s o m e h e a d s fro m t h e T o rc e llo m u se u m , a n d o n th e o th e r s o m e sc a tte re d fr a g m en ts, s tor e d in ja rs , w h ic h h a d b e e n c o lle c te d fr o m t h e s it e , o n th e s a m e is la n d , w h e re th e c h u rc h o f S t. J o h n B a p t is t o n c e s t o o d , I f e lt th a t t h e tw o g ro u p s h a d n o rth in g in c o m m o n w ith e a c h o th e r. In fa c t, t h e l o o s e p ie c e s w e re s im ila r to t h o s e o f th e B y z a n tin e p e r io d fo u n d a t H o s io s Lo u k a s , n e a r D e lp h i, a n d N e a M o n i, o n th e is la n d o f C h io s , tw o c h u rc h e s fo r w h ic h w e p os s e ss g o o d d o c u -m e n ta tio n .

S ig . U rb a n i: C o u ld w e s e e o n e o f t h e s e fo rm s y o u u s e in y o u r r e s e a rc h ?

M m e . A n d re e s cu : I w ill b r in g y o u o n e S a tu r-d a y . I h a v e a q u e s tio n fo r M . La v a g n e . D o y o u h a v e a p h o to g r a p hi c te c h n iq u e w h ic h a ll o w sy o u to t e ll o n e p e r io d o f r e s t o r a ti o n f r o m a n -o th e r?

M . L a v a g n e : N o , w e d O n 't. W h e n it is p o s -s ib le , w e o b t a in a p h o t o g r a p h o f th e m o s a ic w h e n it w a s d is c o v e r e d , b e fo r e r e s t o r a ti o n . I fw e do n 't h a v e o n e, w e tr y to m ak e u p dr a w in g s s h o w in g th e o r ig in a l p a r ts . In re g a r d t o M r .

N o v is ' re m a rks , I w o u ld l ik e t o e m p h a si z e th a tw e a re co n v in c e d th a t s e v e ra l w o rk e rs, s p e ci a -liz e d i n d if fe r e n t p a r t s . h a v e w o r k e d o n t h e s a m e m o s a ic a t th e s a m e t im e . F o r e x a m p le ,a T u n is ia n m o s a ic c a rr ie s a n i n s c rip tio n s ta tin g t h a t a c e r t a in w o r k e r d id t h e s h a d o w s b e h in d th e fig u re s, a n o th e r th e w h ite p a r ts , e tc .

M . B a s s ie r : W e m u s t a d d to w h a t h a s b e e n sa id th a t s ta tis tic a l c a lc u la tio ns pe rm it t he e s ta -b lis h m e n t o f g ra p h s s h o w in g th e p a tt e rn o f s p e -c ific c h a ra c te ri s t ic s o f te s se ra e w h e th e r o u tsi d e th e ir c o n te x t o r re m a in in g in p la c e in a m o s a ic . T h u s w e c a n c le a rl y s h o w t h e c h a r a c te r is ti c d im e n s io n s o f th e te s s e ra e , th e ir s h a p e s , th e ir s ta t is tic a l d is tr ib u tio n b y d im e n s io n s o r b y t he s h a p e o f t h e ir f a c e s , t h e c h a r a c t e r is t ic s o f jo in ts , o f r o w s , t h e d is tr ib u tion of c o lo u rs an d o f

m a te r ia ls . . . W e c a n m a k e a s e r ie s o f s p e c ific d ia g r a m s o f th is o r th a t p a rt o f a m os a ic a n dc o m p a r e th e m w it h t h o s e o f o t h e r m o s a ic s . C o m pa rin g t he g ra p h s p ro v es th a t th e te s s e ra e a re n o t a rra n g e d a c c o rd in g to t h e La w o f G re a t N u m b e rs a n d c o n s e q u e n tly t h e m a th e m a tic a lfu n c tio n s th e y e x p re s s c o rre s p o n d to p a r tic u la r te c h n iq u e s o f s p e c ific a rt is ts , a rt is a n s , s tu d io s a n d a n c ie n t a n d m o d e rn re s to re rs .

S ig . U rb a n i: T h a n k y o u v e ry m u c h . A ll o f th is h a s b e e n v e ry in te re s tin g . I th in k it is im p o rta n t to e m p h a s iz e t h e v a lu e o f a m a th e m a tic a l a n a -ly s is o f m o s a ic e le m e n ts , e s p e c ia lly in a n c ie n tw o rk s .

3 8



CONSERVATION PROBLEMS OF MOSAICS IN SITU

The need to find a way to prevent the destruc-tion of mosaic pavements has become extremelyurgent. The problem has reached alarming pro-portions, not in regard to mosaics preserved inmuseums, but concerning those left in situ inthe excavations, The problem there is dramaticand demands decisions which should never haveto be made.

I speak from excavation experience in OstiaAntica where the problems appears on a ma-croscopic scale. Known mosaics in Ostia coveran area of 10,000 m and, by the time the entiretown is unearthed, the figure is likely to in-crease by half again.

Professionals recognize the 'importance ofkeeping mosaics in the place where they havebeen discovered. We have gone beyond the prac-tice of transforming mosaics into just so manypictures to be hung on museum walls. Here it isthat problems arise, if you can't reconstruct the

by Maria Luisa Veloccia

Translated from the Italian

rooms which formerly sheltered the mosaics orenclose them in a series of sheds. There can bemany reasons for this: costs, the size of thearea to be covered, problems concerning thesite itself, and inadequate knowledge of theheight and roofing of the original buildings. Thedecision to leave mosaics in their original posi-tion, as we shall see later on, brings up a seriesof new problems tied to micro-biological infesta-tion. This infestation must not be neglected, orregarded as a "lesser evil", given our limitedknowledge in the area.

The causes of deterioration are ever-presentand to come extent inevitable in ancient build-ings and can easily lead to the total loss of thework. These causes can be reduced to threebasic related and interdependent groups (Frig. 1).The groups concern the constituent parts of amosaic, such as marble and stone tesserae, andmortar in the support, and, for simplicity's sake,we shall deal with them in the following manner.

Fig. 1 - A mosaic in situ in the process of disappearing because of sinking, calcination, gaps, and infestation bygrass and algae

39



F ig . 2 - P a v e m e n t i n a s ta te of a d v a n c e d d e c a y b e c a u s e o f t h e d is in t e g ra t io n o f t h e n u d le u s f o ll o w e d b y t h e d e s t ru c t io n o f th e s e t t in g b e d a n d t h e b re a k in g o f t e s s e ra e b y p la n t i n fe s ta tio n

D is in t e g r a t io n o f s u p p o r t s is c a u s e d b y :

a ) D e c a y o f m o rta r : E ffe c ts th e s e tt in g b e d . It is d u e to s u d d e n d e h y d ra tio n fo llo w in g e x c a -v a tio n , to th e th in n e s s o f th e m ix tu re a n d g e n -e ra l a g in g . It is c lo s e ly tie d to p la n t in fe s ta t io n .

b ) B re a k in g a n d s in k in g : T h e n u c le u s is th e fir s t t o b e e ffe c te d . T h e c a u s e s c a n b e d u e to th e s e ttlin g , o fte n s lo w a n d g ra d u a l, o f s u p p o rt-

in g s tru c tu re s ; to th e c o m p a c tin g o f th e u n d e r-ly in g g r o u n d ; t o t h e c o ll a p s e o f b e a m s , w a lls a n d ro o fin g , e s p e c ia lly v a u lts , a ll o f w h ic h e n -c o u r a g e f r a c t u r e s in a n d th e s in k in g o f t h e m o s a ic s u p p o rt . T h e s u p p o rt c o u ld h a v e b e e n a lre a d y w e a k e n e d b y th e p e n e tr a tio n o f w o o d y ro o ts .

c ) E a rlie r re s to ra tio n : E ffe c t th e s e ttin g b e d . T h e d iffe re n c e in tim e , e x e c u tio n a n d in th e q u a -lit y o f t h e m o r t a r p r o v id in g lit t le in t e r p e n e t r a -t io n ) c r e a t e s it e s w h ic h i n v ite t h e r o

o t in g o f w e e d s . d ) A tm o s p h e ric fa c to rs : P ro lo n g e d , d riv in g

r a in s , a n d e s p e c ia lly fr o s t , c a n a ls o e ffe c t t h e n u c le u s .

D is in t e g r a t io n .o f t e s s e r a e is c a u s e d b y :

a ) W e a r : T h is v a r ie s w it h t h e h a r d n e s s o f th e t e s s e ra e . T h e m a x im u m a m o u n t fo u n d s o f a r is 0 . 5 c m .

b ) C a lc in a t io n : T h is is c a u s e d b y o ld f ir e s , w h e n th e re w e re fa ls e c e ilin g s m a d e o f c a n e , o r m o d e rn fire s , s e t d u rin g th e s u m m e r to c le a r fie ld s . T h e la tte r b la c k e n a n d c ra c k t h e t e s s e ra e .

c ) D e te rio ra tio n o f th e s to n e : P o ro s ity o f th e s to n e , t h e la c k o f c o m p a c tn e s s in th e m o s a ic a s th e te s s e ra e fla k e a w a y , - p o llu t io n , a n d m ic ro -b io lo g ic a l in fe s ta tio n a re th e c a u s e o f t h is .

M ic r o b io lo g ic a l a n d p la n t in fe s ta t io n d u e to w e e d s , p la n ts w ith b u lb o u s ro o ts , rh iz o m e s , ta p ro o ts , s h ru b s , a lg a e , e tc . (F ig . 2 ), is c a u s e d b y :

a ) S e e d in g : T h is in v o lv e s t h e s e t t in g b e d . It is fo u n d o n e x p o s e d m o s a ic s , o n fre s h o r o ld s a n d c o v e rin g s , a n d o n v o lc a n ic a s h . b ) La c u n a e : F ille d w ith w in d -b o rn e s o il, t h e s e a c t a s v e rita b le s e e d in g b e d s . c ) H u m id ity : T h e in fil

tra t io n a n d c o n d e n s a -t io n o f w a te r in c lo s e d s p a c e s fa v o u r s a lg a e in fe s ta tio n s . d ) L ig h t in g : In s u ff ic ie n t n a t u r a l lig h t in g b e -c a u s e o f s m a ll w in d o w s o r a lim ite d n u m b e r, o r a rti fic ia l lig h tin g u n d e r p a rtic u la r c o n d itio n s . e ) V e n t ila t io n : N o n e , r a r e , o r o n ly in p a r t i-c u la r d ire c tio n s .P o in t s c ), d ) , a n d e ) a p p ly e s p e c ia lly t o m ic ro -b io lo g ic a l in fe s ta tio n s w h ic h g e n e ra lly a p -p e a r in c lo s e d e n v iro n m e n ts .N o w le t u s g o b a c k a n d d e v e lo p th e s e th re e g ro u p s .

D e t e r io r iti o n o f s u p p o r t s

T h is is th e m o s t o b v io u s , th e m o s t s e rio u s , a n d I w o u ld s a y th e m o s t d e c is iv e - c e r ta in ly i n it s e x t r e m e fo r m - s t e p in t h e d e t e r io r a t io n o f m o s a ic p a v e m e n ts . T h e tim e it ta k e s c a n v a ry a c c o rd in g t o c lim a tic a n d e n v iro n m e n ta l c o n d i-tio n s ( in s o m e e x tre m e c a s e s . th e tim e c a n b e v e ry b rie f, e v e n o n ly a f e w d a y s ). T h e a m o u n t o f m a in t e n a n c e a n d fo o t t r a ff ic t h e m o s a ic g e ts a ls o e ffe c t it s r a te o f d e te r io ra t io n .

A t firs t, th e d e te rio ra tio n s h o w s u p a s a k in d o f e la s tic ity u n d e r lo a d s a n d a y ie ld in g u n d e r-fo o t w h ic h is e n tir e ly a b n o rm a l fo r th is k in d o f p a v e m e n t. T h is i s d u e to in s u ffic ie n t c o h e s io n b e t w e e n t h e t e s s e r a e a n d t h e ir s u p p o r t . F o r -m e rly , a t th is s ta g e , in je c tio n s o f liq u id c e m e n t w o u ld b e m a d e t o p r e v e n t th e fo r m a t io n o f b u lg e s a n d c ra c k s , p la in s ig n s o f d is in te g ra tio n . T h is p ro c e s s h a d v e ry m e d io c re re s u lts .

T h is p r o c e s s , e v e n if it is s o m e t im e s u s e d to d a y b e c a u s e o f e c o n o m y a n d u rg e n c y , a lw a y s g ra v e ly d a m a g e s th e m o s a ic . T h e p ro c e s s m a k e s it a lm o s t im p o s s ib le to c o rre c tly c le a n th e b a c k o f th e w o rk a s s h o u ld b e d o n e w h e n i t is b e in g re m o v e d in o n e p ie c e . T h e c e m e n t, in fa c t, b y p e n e tra tin g b e tw e e n t h e te s s e ra e a n d w e ld in g th e m to th e n u c le u s , fo rm s a n e x tre m e ly h a rd m a s s w h ic h , in tu rn , c a u s e s c ra c k s in s u rro u n d -in g a re a s . T h is m a s s c a n n o t b e re m o v e d , e v e n w ith m e c h a n ic a l m e a n s . B e c a u s e o f th is , a fte r th e re s to ra tio n h a s b e e n c o m p le te d , th e s e a re a s o f c e m e n te d te s s e ra e s ta n d o u t fro m t h e o th e rs , e a s ily re c o g n iz e d b y th e ir a rid a p p e a ra n c e a n d lig h te r c o lo u rs .

S u ita b le r e s in s m a y p ro v id e th e a n s w e r to t h e p r o b le m o f a r r e s t in g t h e d e t e r io r a t io n o fs u p p o rts . B e a r in g in m in d th e re q u ire m e n ts o f g o o d c o n s e rv a tio n , th e q u a lit ie s n e e d e d a re s ta -b ility u n d e r h e a t a n d l ig h t, a l

m o s t to ta l re v e rs i- b ility , e a s y a p p lic a tio n e v e n in h u m id a re a s . T h e u s e o f re s in s , h o w e v e r, r e m a in s a n e m e rg e n c y m e a s u r e l im ite d i n ti m e a n d re s tr ic te d t o th e w e a k e n e d a re a s .

4 0



The moment these first signs of deteriorationappear is the ideal time for restoration bydetachment. Lacunae, cracks and displacementshave, as a rule, not yet appeared and the lessen-ed cohesion between the tesserae allows a com-plete brushing of the surface This permits abetter penetration of adhesive between the tes-serae. In addition, only light, brief blows on thechisel are needed to detach the pavement fromits support, thus diminishing the danger of break-ing the tesserae or crushing those which arealready damaged.

This first phase of deterioration generallyappears shortly after the discovery of the mo-saic. It is closely related to the state of preser-vation of the work, to its quality of workmanship,and very often, although indirectly, to its period.

A second phase follows with more striking

manifestations. Disintegration and loss of partsof the mosaic begin. Cracks begin to form andrapidly grow in length and width. Swelling withinthe mosaic forces the tesserae to bulge upward.These breaks are almost always caused by theroots of plants which have worked their waybetween the teserae and the support.

These phenomena are greatly acceleratedin mosaics composed of big tesserae always oflate periods, usually embedded in very dry mor-tar and, naturally, in the rare mosaics set in aquincunx.

Bulges are the most dangerous because they

precede the expulsion of the tesserae them-selves which happens unexpectedly and spon-taneously if there is no conservation treatment,and brings about the loss of ever larger partsof the mosaic. Lacunae originating in this wayare usually roughly circular and often keep theimprint of the lost tesserae for a while. Withimmediate, prudent action, the tesserae cansometimes be replaced, naturally following thedesign remaining in the setting bed.

This type of deterioration is still almost ine-vitable in our days. It is related to the nature ofthe work and to its vicissitudes and consequent-

ly it is at the top of our list. This type of deterio-ration, except perhaps in its First stage, is theresult of a series of causes. The series begins,in the very rare case of a mosaic being discover-ed in a perfect state of preservation, with thesudden drying-out of the structure of the workwhich is already weakened by age. This drying isprovoked by excavations which alter a state ofequilibrium. The weakening is intensified by thesettling which the mosaic has undergone overthe ages.

Although we can't be precise about the lengthof time, because our observations are always

made after the fact, the first stages of disinte-gration occur much more rapidly in late periodpavements. In the later periods, the mortar wasweaker and rougher. Deterioration shows parti-cularly quickly when these late period pave-

ments are composed of tesserae of considerablesize, some of which are cubes of 5 cm' a side.When they are that large, the binder betweenthe rows doesn't have the strength to hold eachtessera in place. Degradation is equally fast inplaces where, for climatic or environmental rea-

sons, or because of their specific position (forexample under a dripping fountain), the mosaicsare subject to the erosion of steady driving rainsor even brief and superficial frosts.

Older restorations are a weak point in thework because of little or no interpenetrationbetween the drier nucleus slab and supportslaid down in later periods. We see the same si-tuation in fresco restorations when the workgoes no deeper than the intonaco.

Fractures in the support are very frequent inheated rooms, in places where the floor beamshave yielded, where vaulting or other heavy ar-

chitectonic elements have suddenly collapsed,or where settling has occured. These fracturesconstitute the usual first step in the process ofdisintegration if it has not already been causeddirectly by the collapse or sinking of the pave-ment itself.

Climatic factors play a fundamental role inall phases of the disintegration of supports.Water in all its forms is the principal agentwhether it be humidity by condensation, infiltra-tion, stagnant water, or ice.

That is the general view, hardly comforting,of the situation. What are the immediate possi-

bilities of a protective intervention that is rela-tively effective and inexpensive? We excludecement Injections, for reasons already given. Onthe other hand, because of technical conside-rations and their still high cost, epoxy resinscannot yet be considered available for large-scale use. We have also excluded immediate andtotal detachment. Aside from roofing over themosaics, which has its drawbacks, there is an-other remedy which is temporary and seasonaland must be renewed every year. This is theapplication of a protective layer. of sterile sandor pozzolana over plastic sheets carefully laidover the mosaic surface, which has previouslybeen thoroughly cleaned and from which all plantlife has been removed. This covering serves tokeep the temperature of the mosaic relativelyconstant and to simultaneously block the infil-tration of water and prevent the reappearanceof plant growth.

Disintegration of tesserae

A basic cause of the destruction of mosaicsis the degradation which the very material ofwhich the.y are composed undergoes, whetherthat be stone, marble, ceramic or glass paste.The fragility of the last two creates .a series ofproblems completely different from the others.But we will leave aside the problems of ceramicand glass paste tesserae because they are sel-

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d o m fo u n d in o u r a re a , a t le a s t in R o m a n p a v e -m e n t m o s a ic s o f th e g oo d p e rio d.

In th e c o m m o n ly e m p lo y e d s to n e te s s e ra e , d e te rio ra tio n s h o w s in s u rfa c e p o ro s ity a n d s c a l-in g o f th e u p p e r, e x te rn a l fa c e . I n s id e t h e te s -s e ra e , th e re c a n e v e n b e fra c tu re s a t th e le v e l o f t h e s u p p o rt , e s p e c ia lly i f t h e s u p p o rt i s p a r -t ic u la r ly s o lid a n d t h e p a v e m e n t is s u b je c t t o h e a v y tra ffic .

It s h o u ld b e p o int e d o u t th a t th is ki n d o fd a m a g e is p a r tic u la rly fr e q u e n t in p o ly c h ro m e m o s a ic s , in w h ic h th e d iffe re n c e in d u ra b ility o f th e m a te r ia ls e m p lo y e d m a k e s it a lm o s t in e v i-ta b le . It is a ls o v e ry c o m m o n in b la c k a n d w h ite m o s a ic s w h e re , to w h ite t e s s e ra e o f a v e ry h a rd lim e s to n e m a te ria l a re a dd e d b la c k te s s er a e o fle s s d ur a bl e s ed im e n tar y m a te ria l.

T h is ph e n o m en o n b a s ic al ly d e pe n d s o n th e ty p e o f s to n e e m p lo y e d . O n ly a n e x h a u s tiv e

q u a -lita t iv e a n a ly s is o f o u r m o s a ic s w o u ld a llo w u s to k n o w b e fo re h a n d w h e re ca s e s o f t h is ty p e o fd e t e r io r a t io n a r e li k e ly t o h a p p e n . A t th e m o -m e n t, a n in v e s tig a tio n o f th is ty p e w o u ld h a ve o n ly i n fo rm a tiv e v a lu e b e c a u se , u n til n o w , th e re m o v a l a n d th e s u b s titu tio n o f c ra c k e d te s s e -ra e h a v e b e e n t he on ly ef fe c tiv e m e a n s o f c o n -s e rv at io n .

A ll o f t h e s e p h e n o m e n a a re a c c e le ra te d b y h is to r ic a l v ic is s itu d e s a n d th e n a tu re o f th e t e r-ra in . P a rti c u lar ly a c id s o il, ric h i n o rg a n ic s u b-s ta n c e s , o r s im p ly d a m p , a id s t h e p r o c e s s o f d e s tr u c tio n . I n th e s a m e w a y , a fire , w

h e th e r it d e s tr o y e d th e b u ild in g in a n c ie n t ti m e s o r w h e t h e r s im p ly a b r u s h f ir e (F ig . . 3 ) a ft e r th e m o sa ic h a s b e e n u n c o v e re d , c a n b rin g a b o u t t h e p ro g re s s iv e d e te r io ra tio n o f th e te s s e ra e e v e n w itho u t c a lci na tio n .

F ig . 3 - P ar ti a l in fe s ta tio n h e lp ed b y c a lc in at io n an d s in k in g

In re c e n t y e a rs a t m o s p h e r ic po ll u t io n h a s b e e n a d d e d t o w h a t w e m ig h t c a ll th e " tr a d itio -

n a l c a u s e s o f t h e d is in t e g r a t io n o f t e s s e r a e . T h e e ffe c ts o f p o llu t io n a re s o w e ll k n o w n a n d c ov e r s u c h a w id e ra n g e , in v o lv in g h is to r ic m o -

n u m e n ts i n th e ir e n tire ty , t h a t t h e y s h a ll n o t b e c o v e re d in th is b rie f a n a ly s is .

T o a v o id t hi s s lo w d e s tr uc tio n o f te s s e rae , w e m u s t h o p e f o r th e d is c o v e ry o f s o m e s u b -s ta n ce w h ic h w ill in c rea s e t he ir d u rab ility. W e d o n ' t y e

t h a v e a s o lid if y in g a g e n t th a t is t ru ly e f f ic ie n t a n d is e a s y to a p p ly , w h ic h w o n 't c h a n g e th e c o lo u r s o r t h e a p p e a r a n c e o f th e w o r k , w h ic h is r e v e r s ib le , a n d w h ic h w o r k s in th e s a m e w a y o n st o n e s a n d o n b in d er s .

P la n t i n f e s t a t i o n

U p til l n o w , w e h a v e e xa m in ed th e d is in te-g ra tion o f m o s a ic p a ve m e n ts t h ro u g h th e d is in -teg rat io n o f th e ir c on s ti tu e nt p a rt s. N o w w e a re g o in g to e x a m in e t h e pr in c ip a l c a u s e o f d isi n-teg rat io n , w e c o u ld d e sc r ib e it a s ex te rna l, w h ic h

s p r in g s fro m th e e n v iro n m e n t a n d n o t fr o m th e n a tu re o f th e w o rk: p la n t in fe s ta tio n . F o r c o n v e n ien c e , t hi s c a n b e d iv id e d in to tw o

m a jo r c a t e g o r ie s : p la n t s w h ic h a t t a c k t h e n u -cl eu s a n d m ic ro - o r g a n is m s w h ic h a t ta c k th e te s s e ra e .

E a c h o f th e s e c a te g o rie s c a n b e s ub d iv id e d in to o th e r in te rd e p e n d e n t g ro u p s w h ic h c o n c e rn t h e t y p e o f p la n t a n d t h e s t ru c tu r a l e le m e n t it e ffe ct s .

G r a s s e s

T h is c on c e rn s i nf e st a tio n b y w e e d s , r o o ts ,b u lb s , rh iz o m e s a n d t a p ro o ts , to c ite th e m o s tc o m m o n , w h ic h im p la n t th e m s e lv e s i n th e m o -sa ic s u r fa c e a n d in t h e s up p o rt . In a ll e x ca v a -tio n s in o p e n c o u n try o r in p la n te d a re a s o f s o m e s iz e , t h e w in d s p re a d s s e e d s o f s o m e p la n ts w h ic h g ro w e a s ily i n c a lc a re o u s o r p a r tic u la r ly po o r so ils. T h e se p la n ts g row in t he fis s ur e s a n d la c u n a e o f th e m o s a ics , o n d e p o s its o f d e c a y in g v e g e ta b le m a tte r , o r in d is in te g ra te d s u p p o rts .

T h e g ro w th o f ro o ts u n d e r th e te s s e ra e a n d a lo n g s tr uc tu ra l l in es is a id e d b y th e a c cu m u la -tio n of a ir -b o rn e m a ter ia l. T h is r ap id ly b u ild s u p

in to a l a y e r o f r e la tiv e ly f e rti le c o m p o s t in w h ic h b ie n n ia ls g ro w , p re p a rin g , in t h e ir tu rn , th e la y e r o f e a r th f o r m o re c o m p le x p la n ts u n til th e s u r -fa c e o f th e m o s a ic is f in a lly c o ve red b y a m a n tle o f v e g e t a t io n . In s u c h c a s e s , th e n e a rl y to t a l d is in te g ra tio n o f th e s u p p o rt ra p id ly re d u c e s t h e p a v e m e n t m o s a ic to a m a s s o f s m a ll p ie c e s o fs to n e .

T h e l is t o f in fe s ta n t s is r a th e r lo n g . It in -c lu d e s p a s tu re w e e d s a m o n g w h ic h , n o te d fo r th e ir d iffu s io n a n d h a rd in e s s , a re c o u c h -g ra s s ,b ro m u s, c lo v er , th e w ild ca rr o t, fe n n e l, a n d b e ar -b in e w h ic h , b e c a u s e o f it s a b u n d a n t, w id e ly - sp rea d in g r o o ts

, is o n e o f t h e w o rs t, m o s t d e-s tr u c tiv e p la n ts a n d o n e o f th e h a rd e st t o e ra -d ic a te.

I t t a k e s ab o u t th ir ty y e a rs fo r a m o s a ic t o c o m p le te ly d is a p p e a r u n d e r a c o v e rin g o f v e g e -

4



tatio n (Fig. 4 ). Under no rmal co n ditions , it should b e possib le to res tore the mosaic d uring su c h ap eriod o f time. In specific c ases, h o wever, it isnot p o ssible es pecial ly if, as a t Hadria n 's Villao r at Os tia , the m o saics alr eady e xc avate d a nd

left n s tu cover m o re than 15 000 m . Thirtyyears a re onl y e nough to study a nd sur ve y, butn o t restore , .the dis coveries of our pr e decess o rs.

F ig. 4 To ta l infestati o n causing the mosa ic to disap p ear

Som etimes o nly two growing season s areen ou gh for t he destru ct ive spr ea d of ro ots . Thes ea re the o nes th a t cause the mo s t impo rt antdam age bec ause the y cause a detac hment o fthe tes s erae, w h erever t h e roots h ave pen e trat-e d, spre ad ing ou t f rom th e origina l p lant. W h entou gh p lant s, or bus hes with woo dy roots ge tint o t he cra ck s, the lac unae of the sl ab , or in togaps in the w alls, the mosaic surface quickly crack s a nd bu lge s (Fig . 5) .

Fig. 5 - C racks in a mosaic c aused b y roots of s h rub

w hich had b een cut o ff above g r ound

Ho w the n can w e interv en e to li mi t, if no tavoid , this kin d of dam a ge?

In the fi rst place , mosaics need to be clean e dconst antly. Bu t howeve r constan t and ca reful thecleanin g , it is al m ost nev e r suffic ie nt to pr e vent

the intrusion of roots and the subsequ ent brea kup of t he supp o rts. Rem oving th e plants b y handd oesn't p revent th em fro m sprin gi ng up a g ainbec au se onl y the pa rt above gr ound h a s been de st royed . F urther mo re, pu llin g the w eeds o ut is on ly po ssib le at the begi nnin g of the infes ta-tion w h en it i s l imited to a few c learly vi siblesp ora dic tu fts. Besi des , ther e's alwa ys t he ris kin thi s proces s of pull ing out t e sserae caughtin the ro ots (F igs . 6, 7 ). C hem ica l herb ici despr o vide a te mpora r y soluti o n to thi s proble m .T hey c om plete ly d estro y t he ma ntl e of v ege ta-t ion in clu ding its r oots, an d allo w t he re mo val

of p lant debr is and th e recove ry of the mosaic w ithou t di sturb ing its t extu re, e ven wh en t hesup p ort is n ea rly des tr oyed.

Amo ng the m an y herb ic ides o n t he ma rke t,we need to choose those w hich de stroy th e plant s ' roots, w hich do not spr e ad thro u gh thesoil, w hic h ac t du ring the winte r, t hus p erm itt-ing remo va l the follo wing su mme r, a nd w hich do not s eem to l eave sa lt depos its. They musta lso be e as y to u se and b e absol ute ly gu ar-an teed non -toxic to hum ans and an imals. He r-bi c ides wh ich simp ly dry u p the ex p osed pa rtof the p lant an d do no t i nterfer e with th e vege-tative pr ocess ar e ent irely inad equ ate.

H erbicid e s becom e indisp e nsable w hen mo -saics are foun d close to the s u rface o r when,for v ari ous re as ons, p rot ective sa nd lay ers have not b ee n rem ov ed for se veral ye ars an d t he in-fe station h as bee n able t o r each t he mosa ic. Inthe p a rticular c ase of O stia, jus t as an e x ample,the ex te nt of th e mosai c s, the e x cavatio n pro-b le ms, th e disturb a nces o f the wa r - the c o n-s e quence s of whi ch are st ill, unfortu n ately, f e lt -a nd the st at e of co ns ervatio n have f or ced us to make o n -the-sp o t decis io ns reg ar ding re st ora-tion and r esetting paveme nts as w ell as in theseas onal op eration o f coverin g the mo saics in win ter a nd c lean ing the m osa ics the r est of the tim e. The u se of ch e mical h e rbicides of the h o r-m ona l typ e se em s to h ave fully sol ved the pro-ble m of we eding, as long as you k eep up a co n-tin ual ca mp aign. It will un co ver a ll th e mo sa icand m arble p a vemen t s and al low a su rvey ofthem .

M icro or ga nisms

This s ec ond ca te gory o f p lant in fes tants m u stbe ex a mined s eparate ly becau s e its ch a racte-ri stics ar e practi c ally the opposit e (Fig. 8 ) of

tho se show n by we e ds, and becaus e it is les sw ides pre ad. W e must als o be ar i n min d t hatthes e remark s are onl y prelimi n ary bec a use our observ a tions a n d expe r iments a re barel y pastthe in itial st ag e.

43



F ig. 6 • In fes ta tion lim it ed to the ga ps in th e m os aic (n o te Fig . 7 )

Fi g . 7 - C o n di t ion of th e p a ve me nt aft e r r em ov a l o f t h egr a ss . T he te s se ra e a re a ll cle arl y d eta ch ed

A lg ae , w h ich a re no t y et co m ple te ly cla s-s ifie d , a tta c k m o sa ic 'su rfa c e s f rom t h e e d g e s o fth e te s s e rae . T he y g e t in to th e g ro u tin g , w h ic his u s u a lly d a m p e r, c o ve rin g it w ith a g re y -b ro w n film , te n d in g t o w a rd g re e n i n t h e b e tte r- lig h te d are as , t a rn ish in g t he co lou rs an d ob sc u rin g the

d e s ign . A t th e m o m e n t, w e c a n 't s a y h o w th e y a tt a c k t h e s u rfa c e o f th e s to n e s a lth ou gh in a ll the ca se s w e 've st u d ied up ti ll n o w th e tes s e rae ,a fte r b e in g a tta c k e d ha ve b e c o m e m u ch m or e p o rou s, ev en w h e n t h e a lg ae le av e t h e su p p o rt s in ta ct . A lg a e gr o w o n ly o n u nd is t ur b e d p a v e -m e n ts an d p re fe r c lo s e d o r c o v e re d p la ce s w h e re th er e is li ttl e o r n o ve n t il a ti on a n d th e lig h ti n g is e qu al ly b a d ( F ig . 9 ). Y e t w e h a v e r ec en tly o b se rv e d t h a t c o lo n ie s o f gr e e n a lg a e c a n flou r-ish in p a rt icu la rly h u m id co n d it ion s ev en in op en , v en tila te d a re as . A s so on as a ro of ha sb e e n ins ta lle d , a c ol o n y o f a lg a e u s u a ll y a p-pe ar s . I ts de ve lo p m en t i s a lw ay s r at h e r s low an d cy c lic al , gr ow in g, fas te r in la te au tum n an dth e m id dle o f s p rin g .

F ig. 9 - De ve lop me nt o f a lg a e o n a m o s ai c in a d a m p an d p o or ly-l igh ted pla c e

E x pe rim e n ts m ad e so fa r, in c o llab o r at ion wit h t he Is titu to Ce nt ra le d el R e st au ro, in dic at e tha t a lg ic id es (m e rth iola te ) s e e m to b e ef fec tiv e fo r a bo ut a ye ar an d a h al f , p ro vid e d t h a t th ea lga e a re a live (F ig s . 1 0, 11 ). W e c a n' t m ak e a ny s u g g e s tio n fo r a lg a e in th e d or m a nt .s ta ge o r fo rlic he n s w hi c h do n' t s e e m t o re a c t to th e s u b -

F ig . 8 - V a ri e d d ev e lo p m e n t of l ich e n s o n a p a r tly s h a de d pa vem en t F ig. 10 - M osa ic in a da rk a nd da m p pla ce b ef o re tre a tm en t

4 4



Fig. 11 - Mosaic after chemical treatment

stances we have used. But we have not yetbegun systematic experiments.

From this necessarily brief examination ofthe causes of deterioration and of their conse-quences, we have seen that the only restorationpractice which can definitely stop these proces-ses appears to be detachment of the pavementand placing it on a new support. All the otherinterventions are only preliminary or temporary,dictated by urgency and the absence of othermeans. How valid is the detachment method?From a critical point of view, it is long and cost-ly, final, in certain aspects. irreversible, and verydebatable.

By experimenting with new substances andtrying new techniques, we are trying to find ameans of conserving mosaics at their place oforigin, without detaching them, by strengtheningthe supports and removing plant infestation. Theanswer to this problem will be found in the mostrigorous experimentation and research, whichcan only be done through equal and friendly collaboration between experts in archaeology andthe applied sciences.

45



D ISCU S SION

The se n o tes d o n o t at te mp t to r e prod ucew ord f or wo rd th e ma ny c omm ents and que-s tio ns . W e h ave , how e ve r, trie d to r e cor d the ess e ntia l poin ts, th u s sh o wing the g ene ra l dir e c-tio n of th e d is cus si on w hich follo w ed S ign o raVel o ccia s lec tu re.

M r. Fei ld en: W e h ave o nly a littl e tim e left ,p erh ap s eno u gh for on e or tw o q ue sti on s.

M . G u illy: M ad am e, wh at ex per ie nce h ave y ouha d wit h lich e ns?

S ign o ra V e locc ia : Th e re a re ve ry fe w lich e nsa t O s tia. W e h a ve th em o nly i n pl a ces w he re or g anic p ast e s w e re u s ed. I d lik e to b ring upthi s p ro bl em a ga in wi th the I sti tut o C e ntr el edel R est a uro a nd w ith D o ttor e ssa G iac o bin i o fth e mi c ro-b io logi c al la b orato ry th e re. W e ha ven t

had m uch succ ess in tre a ting liche n s.S ig. V illa: T he I. C .R. is con duct in g so me e x-

p e rime n ts n o w w h ich w ill e n d in eigh t mo n ths.In reg a rd t o lich e ns, t hey crea t e sp e cia l pro-blem s an d the y re m ore diffi c ult t o tre a t tha n

a lg ae . T he p rod uc ts w e ve t este d giv e som e re-su lts bu t the y req uire a cle an-u p aft erwa rd.Lich en s w ith le av es , h ow ev er , sh ou ld dis ap pe ara fter a sh o rt w h ile. W e ll g et t h e re s ults of th e e xpe rimen ts ne x t Ju n e.

M . Gh ou j: I v e h ea rd ob jec tions a ga ins t th e u se of ce me nt an d l im e. I t s ee ms th at Ita ly use sthe m. W hat do yo u thi nk of usin g cem ent ands an d? Is th at b a d fo r mo sa ics ?

S ign o ra V e locc ia: Th ere s no d o ubt that m o-sa ic s ar e dam aged by t he us e of c e men t beca u seof the fa ct tha t y ou ca n t d o a co m ple te cle an in gof a ll the elem e nts. F urth e rmo re, ev en if cem e ntwi ll p re se rve a m os aic fo r a v ery lo ng tim e , it sex trem e ly un aest hetic . A m osaic on a cem ents uppo rt se ems lifele ss. It s col o urs are f a ded and c ons e que n tly th e y se e m l e ss a tt racti v e th a nth ose o n a m ort ar su pp ort .

M r. Fe ilden : I am grat e ful to Mad ame V elo c -c ia fo r thi s d ipl om at ic rep ly . E xp ert s com in g t oICC R OM alw ay s s ee m to ag re e th at yo u sho u ldn o t us e cem e nt.

6



SOME EXPERIMENTS IN THE USE OF EPDXY RESINS

FOR THE IMPREGNATION OF THE NUCLEUS

Introduction

The fundamental problems confronting therestorers consist of partially or totally rebuild-ing original structural characteristics and pro-tecting the damaged object in order to delayfuture deterioration. Stone, mortar and brick areconstruction materials which have common cha-racteristics. Therefore, a common solution maybe sought for their conservation. In effect, it isadvisable to use just one product in the treat-ment of these construction materials. But whatshould be the principle characteristics of sucha product? In order to answer this apparentlysimple question, we might recommend the fol-lowing list of characteristics:

low viscosity, permitting deep penetration ofthe product;good hydrophilic qualities, allowing absorp-tion by damp materials;sufficient chemical resistance, considerablysuperior to that of the material being treated;high mechanical resistance in order to rein-force the material being treated;no tendency to clog pores, allowing the ma-terial to breathe;little yellowing upon exposure to daylight;low tendency to alter the colour of the ma-terial being treated;toxic qualities fully known so that users cantake the appropriate protective measures.

Numerous chemical products (organic andinorganic) have been tried and recommended asstrengthening materials. During recent years theresins and plastics industry has produced inter-esting synthetic materials. These epoxy resinsare of particular importance. Various experi-ments in impregnation, consolidation and protec-tion of construction materials have been madewith them. We also know that for numerousapplications in the field of impregnation, con-solidation and protection of construction mate-rials, epoxy resins have been used as basiccomponents.

by Giuseppe Marinelli

Translated from the Italian

Why have these resins, widely used for manyyears to resolve difficult and important problemsin various branches of industry and especiallyin civil engineering, attracted the attention ofthose involved in restoration research as wellas technicians in the field? This interest its suf-ficiently justified by their specific properties.

Epoxy resins in the building of the support

For a long time we have been applying thetechnique of detaching and relaying mosaics ona bed of stratified fibreglass impregnated withresin. This technique calls for the applicationof a reversible adhesive on the visible surfaceof the mosaics, already cleaned and scraped andcementing a flat, strong fabric to it.

The detached mosaic is then transported toa restoration workshop.

There it can be placed on a new supportformed by a stratified panel of fibreglass andresins. When this hardens, the cloth which co-vers the visible surface of the mosaic is re-moved.

The panel obtained is light, easy to carry,and the hardened epoxy is extremely stable, con-sidering its size and its resistance to chemicalsand humidity.

Epoxy resins in the impregnation and consolida-tion of the nucleus

Numerous experiments have been made usingXG40/XG41 and XG40/XG42 to strengthen build-ings and monuments. all of which have provedhighly successful. We can cite for example, theMonastery of Saint Benedetto of Bergamo (sand-stone, brick, mortar), the Tower of Cremona(brick and mortar), the Provincial GovernmentPalace at Bergamo (sandstone). the Rossini Thea-tre of Pesaro (wooden structure), the Gates ofRome (wood), etc. These experiments werecarried out by specialized personnel.

Following these impregnations and cosolida-tions of stone, mortar and brick, we considered

47



Fig . 1 - P av em ent of wh ite agg lom er ate be for e tr eat me nt

F ig . 2 - S e c tio n o f p a ve m en t in th e p ro c e s s o f t re a tm en t

Fi g . 3 - T he sa m e se c tio n o f p a v e m e nt aft e r a y e ar . Th isare a is s till we ll p r es erv ed .

u s in g t h e p ro d u c ts XG 4 0 ,1 XG 11 1 fo r s tr e ng th e ni n g th e n uc leu s of mo sa ics .

O n e p a rtic ul a r p ro bl e m a ros e tw o y e a rs a go in t he R om a n c ity o f L u n i w he re th e m a te r ia l

fro m the e xc ava tio ns de te rio rat ed at ex ce ptio na l

sp ee d a s so o n as it w a s b ro ug h t to lig h t- n o ta b lyo ne se ct ion of pa ve m e n t m ad e u p of wh ite a n d c o lo u r e d m a rb le te s s e ra e, h e ld to g e t h e r b y ab e d of so ft lim e m o rta r.

T hi s t y p e o f p av em en t d oe s no t c o n tai n d e-c or ati ve fi g u res a nd th er ef or e i t is m or e an a gg reg at e t ha n a m os aic . N ev ert he les s, the p ro-b lem o f t h e co n s o lid a tion o f th e n u c le u s m a y b e c o n s id e re d id e n tica l t o t h at of an a c tu a l m o sa ic.

T h e C e n tr e fo r S tu d ie s o f th e C a u se s o fDe te rio ra tion a n d M e th od s for C o n s e rva tio n o fW ork s o f A rt 'G ino B oz z a ' of th e C N R w a s g ive nth e r e s p o n s ib ility o f s tud yi n g th e c on se rv a tio n o f t h e o b jec ts d is co ve re d .

In c o o p e ra tion w ith C IB A -G e ig y , n u m e ro u s a pp lica tio ns o f X G4 0/ XG 41 w ere m ad e n s tu

a nd on la bo ra tor y s am pl es in or de r to e va lua tethe p os sib le e mp lo ym e nt of th is pro d uc t in s tre ng th e n ing th e p av em e n ts al rea dy b rou gh t to lig ht an d t h o s e re c en tly e x ca va te d ( Fig s. 1 - 3 ).

B ot h l a b o ra to ry te s ts an d tho se c a rr ied o u tn s t u p r ov ed th e ef fec tiv en es s o f t he tr ea t-

me nt .

O n e m ig h t s ta t e :

A) T h e p en et rat ion o f th e p ro du ct XG 4 0 /X G 4 1 is ex c e lle n t a n d t h a t a s a m p le w a s a b s or b e d th rou gh ou t a d e p th of se v e ral ce nt im e tr e s .

B ) If o ne re m o v e s th e e xc es s res in w ith a s ol -ve n t (fo r e xa m p le m e t hy lc e to ne ) f r o m t he su rfa ce o f th e te ss era e be fo re th e r es in ha rde n s , p ra ct ica lly no c o lo ur va ria tio n o c -cu rs e ve n aft er pr o lo ng ed ex po su re .

C ) C o n s o li d a ti o n c a n b e c o n s id e re d g o o d : i n e ffe ct , th e m a te r ia ls th a t w e re lo o s e b e fo re tre at m e nt we re st ren gt h e n ed a nd co uld e ve n b e m ec ha nic al ly t rea te d i n o rde r t o g iv e th em a sp ec ific f o rm .

D ) T h is c on so lid at ion is p erm a ne nt bo th af ter th e a c c e ler at e d ag in g c yc le ap pr o p r ia te ly c h o s e n f o r t h e s tu d y a n d a fte r e x p o s u re toai r , e ve n in p a r tic u la rly u n fa vo ur a b le c o n d i-tio n s ( for ex am p le t he m ate ria l p er m a ne nt lys e m i-im m e rs e d in w a te r) .

E) T h e t rea tm e n t d o e s n o t o b s tr u ct bu t o n ly lin es th e p o res , t h e reb y im p ro vi n g th e p ro du ct' s re si s ta nc e to w a te r. At th e s a m e t im e , itd o e s no t r e d u c e th e p o s si b ility o f e x c h a n g e o f g a se o u s e le m e n ts b e tw e e n t h e c o re o f t h e m a te ria l a n d t h e a tm o s p h e re .

F o r al l o f th e s e r ea so ns th e p e n e t ra t io n o fe p o xy c o m p o u n d s w a s c o n s id e re d s u c c e ss fu la nd w as us ed fo r t h e co ns o lid at ion o f a rch ae o-lo g ica l m at er ial at Lu ni.

Th e d is cu ss ion w hi c h fo llo w e d th is le ct u re

w ill b e fou nd o n p a g e 5 2 .

48



TH E R EM OV AL OF WE ED S F RO M O UT DO OR MO SA IC SU R FA CE S

b y A lbe rto Vi lla

Tra ns late d fr om the Ita lian by Cy n th ia R oc k w e ll

Arc ha elo g ic a l s truc tur es are co nst ant ly e n-d an g e re d b y a la rge v a riet y o f p la n t fo rm s , ra n g -in g in si ze f ro m tr e es do w n t o ti n y al g ae .

Th is is o ften on e o f t h e p rin c ip a l c a u s es of th e d e ca y o f ru ins , e sp e c ia lly if th e y a re co m -p o s e d of s tr uc tur e s w hi ch a re a lre a d y co llap s in g o r, like an cie n t m os aic su rfa c es , co mp os e d o fs ma ll te sse rae he ld by b ind ers wh ich fre qu e ntl yh a ve lo s t m os t o f the ir c o n s ist e nc y ( F ig s . 1 , 2 ).

C IV ith r eg a rd to th e p ro b le m o f th e c o ns e rv a -t ion of o ut d oo r m os a ic sur fac es, the pr ese nc e o f w e ed s c a n c lea rly c a u se pe rm a ne n t lo ss fo rth e r eas on s g iven be low :

P la n t r oo t s, w h ic h a re of t en ve r y t h ic k , a nd u p to s e v e ra l m et re s lo n g , "d ig e s t" th e b in d e rs ,cau sin g d isp ers ion of t he tes s er a e.

W a te r p en e tr a te s in to th e c ra c ks c a u se d b y the che mi c al a nd m e ch a ni c al a ct ion o f t h e roo tsa nd fr e ez es in win ter tim e, ca us ing fur the rdi s ru p tio n o f th e m os aic su rfac es .

O v er a p e rio d o f tim e, mo sai c pa ve m en ts c an be co m p le te ly o ve r-gr o w n b y v e ge tati o n w h ic hob s cu res the ir l egi bilit y.

A s id e fr om th is kin d o f m a cr o sc o pi c d am ag e ,th er e is al s o d am ag e fr om m o ss , al g ae an d l i-ch e n s w h ic h c an be eq u a lly s e riou s t o d iffe re n t

ex ten ts. I n a dd itio n t o c o rr o di n g a nd - s ta in ing th e t e ss era e, t hes e o rga nis ms , n o ta b ly lich en , ca n u n ifo rm ly c o ve r th e m o s a ic s ur fa ce , c a us in g co rro sio n da ma ge or at l e as t m icro -pe rfo rati o ns o f v ary ing gra vit y.

It h a s a lw a ys b e e n d ee m e d n e ce s sa ry t o u s ed iffe ren t ty p es of m a n ua l an d m ec h an ica l w e ed -in g to e lim ina te p lan t in fes tat ion s .

Ho we v er , it h as be e n o bv iou s fo r s o m e tim eth a t th es e s y ste ms do no t g u ar a nt e e t ruly po s i-tive r es u lts , d u e t o th e fo llo w in g fa c to rs :

Th e ro o ts o f li v in g p la n ts r e si s t e x tr a ct io n an d c ons ide rab le m e c ha nic al f o rc e is of ten re-q u ir e d to p u ll t he m o u t. T h is c a n c au s e q u it e s eri ous da ma ge to the en tire fou nd a tio n o f th em os a ic i ts el f. C o n sid e rin g th a t su c h o pe ra tio n s m us t so me tim es b e re p ea ted se v e ra l tim e s a

F igs. 1 , 2 - E x am p le s of d am a ge cau s ed by t he p res e nc e of w ee d s

4 9



F ig . 3 - C on d iti on o f a m o s ai c p a ve m e nt be fo re t re at m en t

y e ar , it is e a s y to im a gi n e h ow m uc h d a m a ge th is t ype of ma inte na nce ca n p rod uc e .

R o o t f rag me nt s re m a in in p la c e an d th epl a nt s re a pp ea r .

It is d iffi cul t to cle an up ina cce ssa ble ar eas .In c on tras t, c he m ic al h erb ici d es , as ide fro m

bri llian tly av o idi n g the tec h n ic al pro ble ms me n-tion ed abo ve , al s o s av e a gre at d ea l of tim e a n dla b o ur in t ha t a s im ple ap pli c at ion eli m in ate sth e w ee ds wit h ou t th eir ha v in g to be re m o v ed .

In a s im pl if ie d fo r m , w e c a n i nd ica t e t he ty p ic a l c a se s w h e re c h em ic al h er b ic id es b e c om eind isp e ns a bl e :

Pre -ex c av atio n d istu rba nc e s o ver are as w h e rees pec iall y d elic ate rui ns su ch as m os aic s a reex p ec ted to b e f oun d.

In fa c t, i t i s e a sy to im a g in e t he d a m a ge wh ich co uld be cau se d, e ven be for e e xca vat ion,

bu y p u lli ng tip l iv in g p la n ts w ith th e ir r oo ts de e p in a m os aic pa v em en t.

Pr eve nti v e w or k o n m os aic sur fac es dur ing ex c av a tio n . Du ring ex ca v at ion pro jec ts, a g o od de a l o f t im e of te n g o e s b y b ef o re i t is po s s ib le to c o n so li d at e o r d e ta ch th e m o s a ic s u rf a ce s th at a re bro ugh t to lig ht. Dur ing thi s tim e. we eds ca n b eg in t h ei r de str u ct ive act ion .

T he im m e d ia te u s e o f ch e m ic a l w ee d -k ille rs c a n c om ple tel y p res e rv e th e r u in s fr o m the ef -fe ct of n atu ral see din g b efo re c on s erv ati o n w or kb e gi n s.

M ain ten anc e w ork on m osa ic s ur face s k ep to utd o o rs . E s p ec ial ly i n th e c as e o f la rge a r -c ha e ol o gi c al a re as wh e re it is v irtu a lly im p o s -s ible to m a in t ain a con tin uou s l eve l o f re sto -ratio n w or k s, seq ue n ce s o f st ron g te mp era tur ech a ng es, me teo rolo gic al a cti o n, and so me tim es

p e de str ia n t ra ffic, pro du c e n um er o us fis s ure s i n w hi c h a ll k ind s o f ve ge tati o n c an tak e r oot .

U nd er thes e c ircu ms tan ces , in terv en tion wi thc he mi c al h e rbic ide s c a n p re v e n t t h e d am ag e,w hi c h m ay be lig ht a t th e o uts et, from a c ce lera t-ing in to s o m e th in g q ui te s e rio u s. T h e se da n ge rs, h ow ev e r, a re c le a rly ev e n g re a te r in the ca s e o fm os aic s in arc ha e olo gic al a rea s w hic h ha ve bee nex c av a te d a n d th e n ab an d on e d (Fig . 3 ).

n su c h a ca s e, c a re fu l d is in fes t at io n i s re -q u ire d b ef o re an y n ew w o rk is un d e r ta k en (F ig. 4).

T he use of ch e m ical he rbic ide s w hic h h ave b een m enti one d s o fa r m us t ne ver be att em pte db y a n a m a t eu r . S ele cti o n o f t h e p ro p e r ac t iv e e le m e n ts, d o s ag e s, a n d th e m o s t co n ve n ie n t a p -p lic a tio n t e c h ni q ue s a re vit a l f ac t ors in th e s u c ce s s o f th e o p er a tio n a n d i n p ro te c ting th e ruin s fr om ex p os ure to da n ge rou s s ubs tan ce s.

It is o pp o rtu ne to ex a m ine - th ou g h o nl y in pa ss ing , gi v en th e in for ma tiv e n a tu re o f t h is p a p e r - t he ca te g o rie s in w h ic h w e ed ki lle rs ar e g rou p e d . T h e re a re tw o cla s s ifi ca tio n s.

T h e firs t ca teg o ry (m o de s o f ac tion ) in clu des th e fo llo w in g ty p e s o f w e e d- k ill e rs :

An ti-se ed ling (a c t in th e in itia l ph ase s o f ge r-mi n at ion and sp rou t g row th) .

Co nta ct ( act dir ect ly o n th e a er ial o rga ns ofpla nts , w ith imm ed iate ef fec t).

P e n e tr a tio n - w h ich c a n b e f u rt he r d iv id e d in to t w o c at e go rie s :

b y ro o t a bs o rp tio n (w he n t h ey ac t p ri nc i-p a lly t hr o u gh th e r oo t);

b y f o lia ge ab s orp tio n (w he n t h ey ac t pr in-c ip a lly t hr o u g h th e f oli a ge ) .

In th e se co nd cat e go ry (me ch a nis ms of ac -tio n ), w e e d- k ille rs c an be di vi de d a s f ol lo w s:

Fi g. 4 - T h e s ame pa vem ent 60 days aft er a ppli catio n o fch em ical herb icid es

5 0



F ig . 5 - M os a ic su r fa ce p a rti al ly tr ea te d w it h ch e m ic al

m ea n s. N ot e th e p re c is e a n d we ll-d e lim ite d ac tio n o f th e h e rb ic id e

G e rm in a tio n in h ib ito rs A u x in o r au x in -lik e s u b s ta n ce s ho rm on e s )

P h o to s y n th e s is i n h ib ito rs R e s p ira tio n in h ib ito rs

W e h a v e s im pl y lis te d th e c at e g o rie s o f t h is

s e c o n d g ro u p b e ca u s e a m o re t h o rou g h e xp o s i-

t io n w o u ld l e a d u s in t o t e c h n ic a l d is c u s s io n s

w h ic h s e e m b e y o n d th e s c o p e o f th is p re s e n ta -tio n .

L e t u s e x a m in e t h e q u a lit ie s w h ic h a r e in -

d is p e n s a b le fo r a h e rb ic id e :

A b s e n c e o f a n y p h y s ic a l o r c h e m ic a l a c -tio n , d ire c t o r in d ire c t, o n th e r ui ns b e in g t re a te d.

T h e w e e d -k ille r m u s t b e c o lo u rle s s , tra n s p a re n t

a n d l ea v e n o s ta b le in e r t re s id u e s a fte r a p p li-c a t io n , o r a t le a s t n o n e w h ic h c a n n o t im m e -

d ia te ly b e d is p e rs e d b y ra in w a te r. T h e re fo re w e

m u s t e x c lu d e a n y fo r m u la w h ic h is c o lo u r e d ,

o ily o r w h ic h le a ve s p e rm a n e nt t ra ce s o f its u s e .C h e m ic a l n e u tra lity . N o n - t o x ic it y fo r h u m a n s , d o m e s t ic a n i-

m a ls a n d w ild a n im a ls . T h e w id e st p o s s ib le c o n tro l o f t h e ve g e ta -

tio n in fe s tin g th e a re a s to be cl e a re d. A b s e n c e o f m a te r ia l w h ic h m ig h t p o llu te

s u r fa c e o r s u b - s o il w a te r in t h e a r e a b e in g

tre a te d. G o v e rn m e n ta l r e g is tr a tio n a t th e a g e n c ie s

in c h a rg e o f p u b b lic h e a lth . S ta b ility o f th e a c tiv e b a s e , s o th a t it re -

ma in s w it h in t he lim its p r e sc r ib e d fo r t h e ap -

p lic at io n . Th e re s ho u ld b e no la te ra l s e e p a g e w h ic h m ig h t e x t e n d th e h e r b ic id a l a c t io n to

a re a s w h ic h a r e n o t m e a n t t o b e d is in fe s t e d

F ig . 5 ) . E v e n tu a l d e g ra d a b ility t h ro u g h t h e a c tio n

o f m ic ro -flo ra in t he g ro u n d .

A fte r le n g th y e x p e r im e n ta tio n in d is in fe s ta -

t io n o f h is to ri c s ite s c o n d u c t e d b y th e M ic ro -

b io lo g y La b o ra to ry o f t h e Ita lia n C e nt ra l R e st o -

ra tio n In s titu te , a n d ta k in g in to a c c o u n t th e re -

s u lts o b ta in e d o v e r y e a rs o f p ra c tic a l a n d e x -

p e rim e n ta l w o rk , w e c a n s a y t h a t th e fo llo w in g

h e r b ic id e s a r e to b e p r e fe r re d : th o s e o f th e p e n e tr a tin g ty p e , a b s o rb e d th ro u g h ro o ts o r fo li-

a g e , w h ic h in h ib it p h o to s y n th e s is . T h e s e m e e t

a ll t he re q ui re m e n ts w e h a v e lis te d s o f a r.

O b v io u s ly , fo r h o r iz o n t a l m o s a ic s s u c h a s

p a v e m e n ts , h e rb ic id e s b a s e d o n r o ot , or m ixe d

a b s o rp tio n a re p re fe ra b le b e c a u s e th e f o rc e o f

g rav ity k ee p s r es id u a l a m o u n ts o f ro o t a b s o rp -

t io n f o r m u la e i n th e m o sa ic b in d in g m a t e r ia l

F ig . 5 ) . In c o n tra s t, f o r v e r tic a l m o s a ic s , h e rb ic id e s

b a s e d o n fo lia g e a b s o rp tio n a re p re fe ra b le . h e

fo rm u la n e e d o n ly co m e in to c o n ta c t w ith th e

fo lia g e a n d is t h e n c a rr ie d in w a rd , th a n k s to th e p la n t s v a s c u la r s y s t e m , t o e v e ry p a r t o f t h e

o rg a n is m , d o w n to th e r o o ts ; o n c e th e la tte r a re

d e a d , th e y g e n e ra lly d is s o lv e w ith o u t t ra c e .

La rg e r r o o ts . a fte r d ry in g o u t, c a n e a si ly b e

p u lle d o u t w ith o u t d a m a g in g th e r u in s , fo r th e y h a v e g re a tly d im in is h e d in s iz e .

T h e tw o a c t iv e p r in c ip le s g iv e n b e lo w a r e

p a rtic u la rly e m p lo y e d in t h e c a te g o ry o f h e rb i-

ci d es w e h a ve in d ic a t e d . T h e y b e lo n g t o th e

c h e m ic a l g ro u p o f tr ia z in e :

2 -c h lo ro -4 -e th y l a m in o -6 -t e rt- b u ty la m in o- s- tr ia zi ne

C 9 H 6 C N 5 I

c N H 3

C H 5 N H C H H

C h lo r o tr ia z in e H 3

s o lu b ili t y i n w a te r a t 2 0 ° C e q u a l t o 8 .5

p .p .m .;n e u tra l c h e m ic a l r e a c tiv ity ;s ta b le in th e g ro u n d : p rin c ip a l a c tio n th ro u g h ro o t a b s o rp tio n ;

e ffec tiv e a g a in s t a v as t ra n g e o f p lan ts.

2 -m e th o xy-4 -e th y l a m in o -6 -s e c -b u ty l

am in o -s- tr ia z in e

C 10 H 1 9 N 5 C H 3

N j H 3

C H 5 - --- --N H H

M e tho x y triaz in e 2 H5

5



— s o lu b ilit y in w a t e r , a t 2 0 C C , e q u a l t o 6 . 2 0 p .p .m .;

— n e u tra l c h e m ic a l re a c tiv ity ; — p r in c ip a l a c tio n th ro u g h f o lia g e a b s o rp tio n ;— e ffe c tiv e a g ra in s t a v a s t ra n g e o f p la n ts .

T h e tria z in e s w e h a v e d e s c r ib e d , a s id e fro m t h e ir a c t io n o n t h e m a jo ri ty o f p la n t s fo u n d in ru in s , a ls o h a v e t h e a d v a n ta g e o f v e ry l im ite d m o b ility in th e g ro u n d . T h is c h a ra c te ris tic m a k e s it p o s s ib le t o u s e th e m w it h in s t r ic t ly d e f in e d lim its , w ith n o d a m a g e to a d ja c e n t a re a s o r to th e s u rfa c e w a te r .

S ix ty d a y s a fte r a p p lic a tio n o f th e s e h e rb i-c id e s , it is p o s s ib le t o s e e th e fu ll e ffe c t o f t h e ir a c ti o n ; a ft e r t h is t im e o n e c a n ju d g e w h e t h e r In te r t o u c h -u p s a re n e e d e d o n p la n ts o r in z o n e s w h e re th e h e rb ic id a l a c tio n w a s w e a k e r .

T h e b e s t t im e t o a p p ly t h e s e h e r b ic id e s is d u r in g p e r io d s w h e n th e w e e d s a r e g r o w in g

(s p r in g o r a u tu m n ). T h e c h o ic e b e tw e e n th e s e tw o p e r io d s c a n b e m a d e o n th e b a s is o f t h e b e h a v io u r o f th e n o rm a l c lim a te in th e o p e ra tiv e z o n e (a v e ra g e ra in fa ll, te m p e ra tu re , e tc . ) .

T h e h e rb ic id e s c o m m o n ly u s e d h a v e n o t a l-

w a y s b e e n fu lly e ffe c tiv e a g a in s t m o s s , a lg a e a n d l ic h e n s . In o rd e r to re s o lv e th is p ro b le m , th e Ita lia n C e n tra l R e s to ra tio n In s titu te h a s c a rr ie d o u t a lo n g c y c le o f e x p e rim e n ta tio n w ith d iffe -re n t a c tiv e p r in c ip le s . T h is re s e a rc h is n e a rin g s u c c e s s fu l c o m p le t io n a n d th e r e s u lt s w ill b e m a d e a v a ila b le a s s o o n a s a ll th e e x p e rim e n ts a re fin is h e d .

In c o n c lu s io n , o n e c a n s ta te th a t c h e m ic a l t r e a t m e n t o f in fe s t a t io n is a t r u ly u s e fu l a n d irre p la c e a b le in s tru m e n t, w h ic h m a k e s a r a tio n a l c o n tr ib u tio n to th e p re s e rv a tio n o f o u td o o r m o -s a ic s u r fa c e s f ro m a t t a c k b y w e e d s - a tt a c k s w h

ic h a re a m o n g th e m o s t a c tiv e c a u s e s o f p ro -g re s s iv e d e c a y .

D IS C U S S IO N

T h e s e n o t e s d o n o t a t te m p t t o r e p r o d u c e w o rd f o r w o rd t h e m a n y c o m m e n ts a n d q u e s -t io n s . W e h a

v e , h o w e v e r , t ri e d t o re c o r d t h e e s s e n tia l p o in ts , t h u s s h o w in g th e g e n e ra l d ire c -t io n o f t h e d is c u s s io n w h ic h fo llo w e d t h e l e c -tu r e s o f S ig . V il la a n d S ig . M a r in e lli.

S ig . U r b a n i: I w o u ld l ik e to a s k S ig . V il la to b e k in d e n o u g h to s p e c ify th e le n g th a n d th e fr e q u e n c y o f t h e s e h e r b ic id e a p p li c a ti o n s . It w o u ld a ls o b e i n te re s tin g if S ig . M a rin e lli w o u ld g iv e u s in fo r m a t io n o n t h e a p p lic a t io n o f c h e -m ic a l c o m p o s itio n s .

S ig . M a rin e lli: T h e s o lu tio n is a p p lie d w ith a p a in t b ru s h . T h is a llo w s y o u to fe e l th e s u rfa c e o f th e m o s a ic a n d m e a s u re th e s p e e d o f a b s o rp -t io n . T h is tre a tm e n t s h o u ld b e c o n tin u e d u n til t h e d e s ir e d d e g r e e o f p e n e t r a t io n h a s b e e n re a c h e d .

S ig . P a p a ra tt i: W h a t is t h e r e v e rs ib ility o f th e re s in s ?

S ig . M a rin e lli: H e a t-h a rd e n e d p ro d u c ts a re n o t r e v e r s ib le . A c o m p lic a t e d p r o c e s s u s in g fla m e w o u ld b e n e e d e d to r e m o v e th e m .

M . L a v a g n e : W h a t d o th e s e tr e a tm e n t c o s t? F o r e x a m p le , h o w m u c h w a s s p e n t o n th e tre a t-m e n t a rt L u n i?

S ig . M a r in e lli: I c a n 't g iv e y o u t h e e x a c t d e ta ils ; o u r c o m p a n y s e lls th e s e p re p a ra tio n s a s c h e m ic a l p r o d u c t s . H o w e v e r, t h e y 'r e n o t e x -

p e n s iv e , a b o u t L it. 4 ,0 0 0 a k ilo g ra m m e . T o t h is s h o u ld b e a d d e d th e c o s t o f a p p ly in g i t.

M . N o v is : I 'v e a tte m p te d tr e a tm e n ts lik e th is fo r y e a rs . H o w c a n t h e s o lu tio n p e n e tra te v e ry c o m p a c t m o s a ic s ? h a v e u s e d it o n th e b a c k s o f m o s a ic s b u t it h a s n e v e r p e n e tr a te d to th e irs u r fa c e s . W o u ld l o w v is c o s it y b e e n o u g h fo r p e n e tr a tio n ?

I h a v e a n o th e r q u e s tio n . In a n o th e r p a v e m e n t, th e st o n e s b e c a m e p u rp le . T h is m ig h t h a ve b e e n b e c a u s e o f c o n ta m in a tio n b y s e a w a te r , b u t in a n y c a s e th o s e m o s a ic s h a d t o b e d e s tro y e d .

S ig . M a r in e lli : A lt h o u g h 'm n o t a re s t o r e ra n d I h a v e h a d h a r d ly a n y e x p e r ie n c e in t h a tfie ld , I b e lie v e th a t im p re g n a tio n is o n ly p o s s ib le w h e n t h e re is a s u rfa c e a b le t o a b s o rb t h e p ro -d u c t. A v e ry c o m p a c t s u rfa c e w o u ld m a k e p e n e -tra tio n fro m a b o v e d iffic u lt. C o n s e q u e n tly , o n ly t h e l e s s c o m p a c t m o s a ic s c a n b e t r e a t e d in th is w a y .

In r e g a rd t o t h e c h a n g e in c o lo u r , th e re 's a la r g e v a r ie t y o f e p o x y s o fte n e r s a n d s o m e o f th o s e re s in s c o u ld h a v e th is e ffe c t. T h e a m in e s , fo r e x a m p le , k n o w n fo r th e ir c o lo u r s tre n g th e n -in g p r o p e r ti e s , e s p e c ia lly in fo o d c o lo u r in g s ,c o u ld b e th e re a s o n fo r th e c h a n g e . T h a t m ig h t b e t h e e x p la n a tio n o f w h a t h a p p e n e d .

M . B a s s ie r : I f y o u w il l p e r m it m e . I w o u ld lik e to m a k e tw o re m a rk s .

F irs t, o n e o n ly im p re g n a tin g p ro d u c t d o e s n 't e x is t, h o w e v e r e x ce lle n t i t m a y b e . T h e im p re g -

5



n a ting ma teria l sh o uld b e ch os e n a c co rd ing toth e na tu re a n d t he c h ar ac te ris tic s of th e su p -

p o rt, o f it s ch a ng e s. a n d th e ca us e s o f th e se

cha n ge s . Th e co m po s itio n of th e n u cle u s a n d th e ru d us a re n ot al wa y s p h ys ic ally t he s am e . W e

m u s t b ea r in m in d m an y di ffe re nt fa c tor s an d m a ke e xp e rim e nt s be fore b eg inni n g w ith i m -

p re gn at ion s. Im pre g na tio ns a re o pe ra tio n s w ith u n ce rt ain

res u lts, h aza rdo u s, a n d t o be avo ided as m uc h a s p o ss ib le. O ne pro d uc t alo n e c an' t res o lve

al l p ro ble m s. Sec ond ly, if the n ucle us is cha nge d, it s duc e

to old, con temp orar y or perm ane nt re aso n s. F is-s ures and mic ro-f issu res a re o nly s urfa ce p he-no m en a. It co u ld be d a ng er ou s to us e pr od u cts w hich see m t o so lve o bvio us p robl ems , the re-s ults of h idde n str e sse s, a n d th us t o cam ou flage

th e r e al r e aso n s o f th e tro u ble . Sig . Ur b ani : Wh a t ki n d o f str e sse s ?

M . B assi e r: C hem ical , phy sica l an d pa rticu -lar ly m ech anic al s t ress es, diffe ren ces in th e

ra te o f se ttlin g , th e pre s su re s o f ex p an s ion a nd co n tra c tio n , a nd t he d a ng e rs o f a ny f or m o fh um idity , esp eci a lly w he n it i s blo cke d by an

imp e rm e abl e lay e r.

S ig. U rba ni: I don t un d ers tand . Are you que -stio ning the valu e of any kind of i m pr e gna tion ?

M r. B ass ier: T he impr e gna tion of th e nu cleu s

se e ms a v a ry d elic a te, haz a rd o us o pe ra tio n ,w h en y ou c an t con trol a ll th e fa c tor s , es pec ia l-ly h u mi di ty.

Si g. T or ra ca : I w o uld l ike t o as k Si g. M ar i-ne lli s o me que stio n s o n th e for m ul a for soli d i-fica tion. You hav e sa id th ere a re n o by -pro duct sb ut t h e f o rm u la s how s th at s o me OH gro ups rem ain . Co u ld t h ey reac t wit h the so lidifie r an dfo r m w ate r ? O n th e o t her han d , if the y do n t

re ac t, th e fin al pr od uc t wo ul d be a bs or be nt .

Sig . M a rin e lli: T he s ol id ific a tio n re a cti o nc o nce rns o nly th e e p ox y gro u ps . The OH g ro u ps

a re di str ib ut ed in t he p ol ym e r an d do n 't h a ve ab s orb e nt c har a cte r istic s. P olym er i s trid ime n -sio n al a nd c ons e que ntly t he O H g rou p s ar e ca p -ti ve a n d c a n't d raw wa t er fr om t he a ir. T he s e

O H g ro up s are p ro ba bl y mo s t re s po ns ibl e for th e

a dhe sive pro pert ies of ep o xy resin s.

M . Gh o uj: In J or da n, we u se l im e an d cem e nt u nd er m o sa ics . W ou ld yo u re co m m en d th e us eof varn ish to pr o tec t the m fr o m r ese e din g aft erh e rbi c ides hav e be en u sed ?

M . V illa : A n y pr ot ec tiv e film ca n be a p pli ed a fter t he h erb icide . Va rnish sho uld b e u s ed first. I se e no thin g ag a ins t it.

S ig . T o rra c a: W ha t kin d o f var n ish d o y ou use ?

M . Gh o uj: A w h ite o r c o lou rless var n ish so

as n ot to e ffe ct th e co lo ur s- in th e m o sa ic.

M . Ba s sie r : I'm op pos e d t o us ing v arn ish o n m osa ic s u rfac e s, e spe c iall y on t hos e in s itu

fo r tw o rea s on s :

Fir s t, s e alin g hu m idi ty in to th e ski n of th e m o-s ai c spe e ds u p ph ys ic al an d ch em ica l c ha n ge s.

Sec o ndly , be caus e va rnis h ch a nge s th e loo kof the s urfa ces of t h e te sse rae. It s eno u gh toco m p ar e a pie c e o f va rn ish e d m arb le w ith a n -ot h er, clea n , p iece to u n der stan d th e ae s the ticda nge r.

S ig. U rba n i: I c an und e rst a nd y our poi n t of view . N e ver thele ss, perh aps a lig ht c o at w oul d act like a mi c ro- c rys ta llin e wa x an d p rotec t the sur face . We don t kn ow w ha t va rnish is u sed ; is it gu m -la c?

M. G hou j: Ye s.

Si g. U rb a ni : F o r la c k of tim e , w e h a ve t oclo se t h e d iscus sion her e . It c erta inly has show nth at p rese rving mo saics n s tu po s es g rea t pro -b lem s an d tha t co nsid e rab le re sear ch is nee ded in t h is f ield .

5 3



F ig . 1 - H a lf do m e v a u lt, d e ta il, o f G y m n a s iu m -Ba th C o m-p le x , S a rd is , T u rke y , 2 n d c . A .D . T h e p la s te r is

ap p lie d i n fiv e la y er s in a m a n n e r d e s c ri b e d b y V itru v iu s . A lth o u g h n o m o s a ic s a re in s it u th e d e p re s s io n s m a d e b y c u b e s in th e s e tt in g b e d a re vi si b le

TH E C L E A N IN G C O N S O L ID A T IO N A N D T R EA T M E N T O F W A L L M O S A IC S

b y L a w r e n c e M a je w s k i

O rig in a l te x t in E n g lis h

T h e te c h n iq u e s o f c o n s tr u ct io n o f w a ll m o -s a ic s a n d th e c o n s e rv a tio n o f m u ra ls m a d e f ro m te s s e ra e a s h e re in d is c u s s e d a re b a s e d o n th e p e rs o n a l o b s e rv a tio n s o f th e a u th o r d u rin g y e a rs s p e n t a s th e D e p u t y F ie ld D ir e c to r o f th e B y -z a n t in e In s t it u t e o f A m e r ic a in Is t a n b u l fr o m 1 9 5 6 to 19 6 0 a n d a s C h ie f C o ns e rva to r o f t h e A rc h a e o lo g ic a l E x p lo ra tio n o f S a rd is , T u rk e y , fro m 1 9 6 4 t o t h e p re s e n t. D u r in g t h e s e y e a rs o f fi e ld a c t iv it y t h e c o n s e r v a ti o n w o r k o n w a llm o s a ic s w a s c ar r ie d o u t in t h e f o llo w in g m o -n u m e n ts in Is ta n b u l: S t. S o p h ia , K a riy e D ja m i (C h u rc h o f O u r S a v io u r in C h o ra ) , a n d F e th iy e D ja m ii (C h u rc h o f S t. M a ry P a m m a k a ri s to s ) . A n u m b e r o f c o n s e rv a to rs a n d lo c a l t e c h n ici a n s , n o ta b ly E rn e s t H a w k in s , C e rr o W a le s, a n d C o n -s ta n tin e T s a o u s is , p a rtic ip a te d in th e w o rk w h ile th e a r t h is to ria n a n d a c h ite c t, P a u l U n d e rw o o d .w a s th e f ie ld d ire c to r o f th e B y z a n tin e I n s titu te . A t S a rd is w o rk o n m o s a ic s w a s p r in c ip a lly o n flo o r p a v e m e n ts in th e G re a t S y n a g o g u e o f S a r-d is , t h e G y m n a si u m c o m p le x , a n d th e se c to rs d e s ig n a te d P a c to lu s C liff a n d P a c to lu s N o r th . H o w e v e r, in e a c h o f t h e s e s e c to rs s m a ll f ra g -

m e n ts o f w a ll m o s a ic s w e re e x c a v a te d a n d o n s o m e m a s o

n ry w a lls m o s a ic s e tt in g b e d s r e -m a ine d i n s it u

A w a ll m o s a ic m a y b e d e fin e d a s a d e c o ra -ti o n e x e c u t e d o n a v e rt ic a l o r v a u lt e d s u r fa c e w ith t e s s e r a e o r c u b e s o f n a t u r a l s t o n e s c o -lo u re d a n d n e a r ly c le a r g la s s , g ild e d g la s s , o c -c a s io n a lly g la z e d c e ra m ic s , b r ic k s a n d, r a re ly , p ie c e s o f m o th e r-o f-p e a rl . T h e t e s s e ra e a re in a fo u n d a tio n o f lim e p la s te r . V it ru v iu s a n d P lin y d e s c r ib e th e p re p a ra tio n o f w a lls fo r p la s te rin g , th e p ro c e du re s fo r m a k in g lim e a n d im e p la s te rs an d th e ir a p p lic a ti o n to th e w a lls in se v e r a lc o a t s u p t o s ix o r s e v e n l a y e r s o f p la s t e r in s lig h t

ly d iffe re n t c o m p o s itio n s a n d c o lo u rs fo r a s u p p o rt o f m u ra l d e c o ra tio n s (1 ). H o w e v e r , th e n u m b e r o f p la s te r l a y e rs g e n e ra lly fo u n d a s a fo u n d a tio n fo r w a ll m o s a ic s ra re ly e x c e e d s th re e in n u m b e r a lth o u g h o n e e x a m p le d o e s e x is t a t S ar d is w h e re fiv e d ist in c t co a ts m a y b e o b se rv-e d . T h is i s a h a lf d om e in o n e o f t h e n ic h e s s u r-ro u n d in g th e l a rg e p o o l o f t h e S a rd is G y m n a -s iu m -B a th c o m p le x a n d p ro b a b ly d a tin g fro m t h e 2 n d c e n tu r y A . D . (F ig . 1 ) . T h e m o s a ic c u b e s fro m th e h a lf d o m e h a v e a ll fa lle n a lth o u g h im -p r e s s io n s o f t e s s e r a e r e m a in in t h e t o p th in la y e r o f w h ite p la s te r a n d t h e lo w e r f o u r l e v e ls a re in v a ryi n g s h a d e s o f p in k a n d

g re y .W a ll m o s a ic s e t t in g b e d s a re p r e p a re d b y m ix in g lim e p u tty , in e r t m a te ria ls s u c h a s s a n d , p u lv e riz e d s to n e s , s tra w a n d o th e r o rg a n ic m a -te ria ls a n d w a te r. T h e l im e i s p re p a re d b y h e a t-in g lim e s to n e a n d /o r m a rb le (c a lc iu m c a rb o n a te ) in a k iln to a t e m p e ra tu re a b o v e 9 0 0 °C a t w h ic h te m p e ra tu re c a rb o n d io x id e is e x pe lle d a n d c a l-c ite is c o n v e rte d in to c a lc iu m o x id e . T h e o x id e is s a tu ra te d w ith w a te r w ith th e e v o lu tio n o f a g re a t a m o u n t o f h e a t a n d c a lc iu m h y d ro x id e o r lim e p u tt y i s p ro d u c e d . T h is s lak in g o f li m e s h o u ld e x t e n d o ve r l o n g p e ri o d s in a lim e p it to e n su re c o m p le te c on v e rs ion

fr o m t h e o x id e to t h e h y d ro x id e . W h e n th e l im e p u tty i s m ix e d w ith in e r t fille rs a n d w a te r a n d t h e lim e p la s te r is e x p o s e d t o t h e a ir , c ry s ta ls o f c a lc it e a r e fo rm e d a s t h e h y d ro x id e c o m b in e s w ith c a rb o n d io x id e f ro m a m b ie n t a ir . T h es e c a lc ite c ry s ta ls

5 4



F ig . 2 - M o s a ic in a s o u t h - w e s t ro o m o f S t . S o p h ia .

T h e fi r s t l a y e r o f p la s t e r w it h t ro w e le d s u r fa c e

is v is ib le o n th e ri g h t

F ig . 3 M o s a ic o f S t . P a u l in t h e K a r iy e D ja m i Is t a n b u l

an d p ar t o f th e De is is . A r ea s of p ain te d p la ste r

a re v is ib le w he re c u be s h a v e fa lle n ou t

4 0 4 •• : •̀

4 • 1 4 A t •41.4 4‘xtr olec1 0 4 it l i a g it ; i lA r

F ig . 4 - D e t a il F ig . 3 s h o w in g c le a r ly t h a t a tr u e f r e s c o

w a s p a in t e d o n w e t pl a s te r t o g u id e th e m o s a ic

s et te r

b in d t h e in e r t m a te r ia ls t o g e th e r in t o a h a r d

a n d d ur a bl e s u r fa c e a n d lo c k t h e te s s e ra e r in p la ce .

T h e v a rio u s l a y e rs o f p la s te r , u s u a lly th re e ,

g e n e ra lly v a ry s o m e w h a t in c o lo u r a nd c o m p o -

s itio n . T h a t w h ic h is a p p lie d d ir e c t ly t o t h e m a s o n r y t o c o v e r i r r e g u la r iti e s in t h e s t o n e

a nd /o r b ric k w a ll o fte n c o n s is ts o f o n e p a rt li m e

p u t ty t o a b o u t t h r e e p a r t s in e r t m a te r ia ls o f

u s u a lly a m ix tu r e o f s a n d a n d b r ic k d u s t a n d

s o m e tim e s w ith t h e v o lc a n ic as h m a te ria l p z

z o la n a T h e p o w d e re d b ri c k im pr o v e s th e d u ra -b il it y o f t h e p la s t e r a n d po z zo la na m ak e s th e

p la s te r o f a h a rd n e s s lik e P o rt la n d c e m e n t. O n e

m a y a ls o fin d b its o f c h a rc o a l, s e a s h e lls , m ic a

a nd ot h e r e x tra n e ou s f ille rs in t hi s fir s t p la s te r

la y e r. S in c e th e m a s o n ry m a y b e q u ite irre g u la r ,

t h is p r e lim in a r y p la s te r c o a t in g m a y v ar y s in

t h ic kn e s s fr om o n e or t w o c e nt im e t r e s u p to

ten or m o re an d i s g e n e ra lly p in k or l ig ht g re y in c ol ou r . T h e s ur fa c e is o fte n t ex tu red w ith t he

tr o w e l t o p r o v id e a m e c h a n ic a l b o n d f o r t h e

n e x t c o a t F ig . 2 ). T h e s e c o n d p la s ter l a y e r is

o fte n r ic h in o rg a n ic m a te ria l s u c h a s s tra w , h a ir

o r o th e r f ib ro u s s u b s ta n c e s a lo n g w ith s a n d a n d

p u lv e riz e d ol d p la s te r a nd s o m e tim e s o ld m o s a ic

c u b e s t h a t a r e fo u n d in r e u s e d fa lle n p la s t e r

e m p lo y e d a s a n in e r t fil le r. T h is l im e s t ra w

in er t in or g an ic m ix tu re m ay b e q u ite th ic k a nd

is u s u a lly of a b ou t th e s am e th ic kn e s s ov e r th e

e n tir e w a ll p e r h a p s tw o to f iv e c e n t im e tr e s.

Th is i nt e r m e d ia te la ye r m a y a ls o b e g iv e n a

s lig h tly te x tu re d s u rfa c e to e n s u re g o o d a d h e-s io n o f t h e fin a l s e t t in g b e d p la s t e r . A lt h o u g h

it h a s b e e n re p o rte d th a t c o m p o s itio n a l s k e tc h e s

h a v e b e e n m a d e o n th e a r ri cc io th e a u th o r h a s

ne v e r o b se rve d s u c h e q u iv a le n ts o f th e s in o p ia

o f s o m e p er io d s of fr e sc o p a in tin g F ig. 2 ).

5 5



ie le o rm .r

.. •9. -- .. . -

-o w e s . 2 1 0 1

P;o mpo si;1 0 1..

T h e t o p la y e r o r in to n c o is u s u a lly . a fin e w h it e p la s te r c o m p o s e d o f a m ix tu r e o f lim e p u tty , m a rb le d u s t, a n d p e rh a p s s o m e f in e s a n d o r s if t e d r e u s e d o ld p la s t e r . T h is is a p p lie d in a g io rn to o r a n a re a th a t c a n b e s e t w ith te s -s e ra e in o n e d a y , a lth o u g h u n lik e t

h e p la s te rs in b u o n fr e s c o p a in t in g it is v e r y d if f ic u lt t o o b s e rv e w h e re o n e d a y 's p la s te r e n d s a n d th e fo llo w in g d a y 's p la s te r b e g in s . T h e in to n c o p la s te r is p a in te d in tr u e fre s c o v e ry s o o n a fte r its a p p lic a t io n , o ft e n w ith c o m p le t e m o d e lin g o f d e ta ils s o th a t t h e m o s a ic s e t te r h a s m e re ly t o m a tc h c o lo u re d c u b e s to p a in te d p la s te r a s h e s e t s t h e c u b e s o n e b y o n e u s in g a p p r o p r ia t e to o ls to b re a k a n d tr im in d iv id u a l c u b e s w h e re n e c e s s a ry to f o llo w th e b ru s h w o rk o f t h e p a in -t e r . In a n u m b e r o f m o s a ic s in B y z a n t in e m o -n u m e n ts in Is ta n b u l th e c u b e s h a v e b e e n lo s t b u t th e p a in te d s e ttin g b e d re m a in s , s o m e tim e s w it h t in y b it s o f th e b o t to m s o f t h e c u b e s s t ill in s itu (F ig s . 3 a n d 4 ). A n d in t h e F e th iy e D ja m i t h e r e a r e la r g e s e c t io n s o f p a in t e d in to n c o w h ic h h a v e b e e n s e t w ith o n ly a fe w c u b e s a s in th e f e e t a n d h a n d s o f th e V irg in a n d S t. J o h n th e B a p tis t in th e b e m a o f th e a p s e o f th e m o r-tu a ry c h a p e l. H e re p a in te d a re a s a re o u tl in e d w ith m o s a ic c u b e s a n d p e rh a p s t h e p la s te r w a s h a rd e n in g a n d in te rm e d ia ry , a re a s w e re n o t s e t .

T h e re m a y n o t h a v e b e e n q u a lity c o n tro l a n d th e m o s a ic s e tte rs k n e w t h a t t h e l a c k o f to ta l s u r -fa c e c o v e ra g e w ith c u b e s w o u ld n o t b e d e te c te d b y o b s e rv e rs a t s o m e d is ta n c e fro m th e s e d a rk v a u lte d a re a s .

In S t. S o p h ia , in th e m o s a ic o f L e o V I b e fo re C h ris t E n th ro n e d , th e m o s a ic is t ta k e s a d v a n ta g e o f th e l o c a tio n h ig h a b o v e t h e o b s e rv e r. H e re c u b e s a re w id e ly s p a c e d , p a r tic u la rly in th e g o ld b a c k g ro u n d , w h e re c u b e s a re s p a c e d fa r e n o u g h a p a rt th a t a d d it io n a l ro w s c o u ld h a v e b e e n i n -s e r t e d . T h e s e g o ld c u b e s a r e t ilt e d a b o u t 3 0 0 fr o m t h e v e r t ic a l s o t h a t f ro m th e f lo o r o f th e in n e r n a rth e x t h e g o ld b a c k g ro u n d a p p e a rs t o b e c o m p le te ly c o v e re d (F ig . 5 ) .

W a ll m o s a ic s h a v e b e e n c a lle d p a in tin g s e n -c ru s te d w ith b its o f g la s s a n d s to n e to s u g g e s t c o m p o s itio n s in p re c io u s g e m s a n d m a d e to la s t fo r e v e r . M a n y a r e s u r p r is in g ly w e ll p r e s e r v e d a ft e r c e n t u r ie s o f n e g le c t b u t lik e o t h e r w o r k s o f m u ra l' d e c o ra tio n th e y re q u ire c o n s e rv a tio n a t te n tio n fr o m t im e to tim e . W ith o u t d o u b t th e g re a te s t c a u s e o f t h e ir d e te r io ra tio n , o th e r th a n w a n to n d e s tru c tio n , is w a te r s e e p a g e u p fro m th e g ro u n d , fro m le a k in g ro o fs a n d w a lls , a n d w a te r c o n d e n s a tio n . W a te r w e a k e n s a n d d is -s o lv e s p a rts o f th e p la s te r s u p p o rt a n d a c ts a s a c a r r ie r o f d e s tr u c t iv e c h e m ic a ls a n d s a lt s .

F ig . 5 - D e ta il o f th e Le o V I m o s a ic in S t. S o p h ia s h o w in g w id e s p a c in g o f c u b e s in th e g o ld b a c k g ro u n d . T h e s e u b e s w e re s e t at a n a ng le t o th e ve rtic al . to g iv e a n illu s io n o f a s o lid

5 6



F ig . 7 - D e ta il o f a c ra m p be ing in s er te d in to a w a llm o sa ic

F ig . 8 - Dr a w in g o f a cr a m p in a w all mo sa ic

Fig . 9 - Di a gr a m of a cr am p in ser ted into a wa ll m osa ic

F ig . 1 0 - D ia g ra m o f a c ra m p ins e rte d i n to a w a ll m os aic

F ig . 6 - D o m e of the F e thi y e D ja m i in I s tan bu l du rin g c o ns e rv a tio n. C o v er in g p la s te r ha s b e e n re m o v ed fro m t he

lo w e r p a rt o f th e m o s ai c a n d c ra m p s h a ve be e n u se d t o re a tt a ch th e m o sa ic to t h e m a s on r y

O x ide s o f s u lp h u r co m b ine w ith w a te r t o p ro d u c e

su lfur ou s a n d sulfur ic a ci d s w h ich dis so lve ca l-

c ite a n d co n v e rt it in to g y p s um . G y p s u m o c -

c up ies a b ou t tw ic e t h e vol um e a s c al c ite an d inth e p roc e ss m osa ic c ub es as we ll a s w ho le a re asof pl ast er ma y b e los t. V a r iou s wa ter so lub le

s alt s tr an sp o rt e d thr ou gh th e s ett ing be d wil l

for m c ry s ta ls a s th e w at e r e v a po ra t es a t th e

sur fac e j ust be low th e c ub es wi th res ult ing mo -v em e n t a nd lo ss of cu b e s a s s alt cr y st a ls ar e fo rm e d.

Pro bl em s o f c on se rva tio n o f w al l m os aic s

in c lu d e : 1 . C on se rva tio n a n d r e p ai r o f th e w a lls ,v a u ltin gs a nd ro o fs . 2 . P ro v is io n fo r pr o p e r dr a in -

ag e an d w at e r b ar rie rs to p reven t w at er ris ing

in w a lls by c a pi llar y a c tio n. 3 . P ro vis ion fo r a d e -q u a te a ir c irc u la tio n t o p re v e n t co n d e ns a tio n a n d ma int ain m ois tur e e qu ilib riu m wit hin th e r oo mh o u s in g t h e m os a ic . 4 . In v e s tig a tio n a nd tr e a t-m e n t o f cl e a va g e o r p o s s ib le s e pa ra tio n o f th e p la s te r lay e rs fro m the m a so nr y . 5 . T rea tm en t of c lea v ag e b et w e e n the la y er s o f pl ast er. 6. Tre at -m en t o f d eca y, de sic cat ion an d d et eri o ra tio n o fse tti n g pla st e r. 7. Re att ac h m en t o f in div idu al

lo o s e cu b e s . 8 . C le a n ing of cu be s a nd in te r -

s tic es . 9 . C o ns oli d at ion of ed g e s o f lo s s. 1 0 Fil l-ing or ot h er tre atm e nt o f l a cu na e, and 1 2. F in alp re se n tat io n .

F ou nd at io n s o f s t ru c tu r es . w al ls a nd ro of s

m u st firs t b e r e pa ire d b ef ore a ny tre atm ie nt isa p p li e d t o t he w a ll m o s a ic o r i ts se t ti n g b e d .

Th is m ay in vo lve re p la cem e n t o r r ep a ir of lea d,ti le s or ot h e r ro o fin g or ev e n re p la ce m e nt or

re p a ir o f a rc h ite c tu ral e lem e n ts . D rai n a ge s ys -te m s m ay be in ne ed of rep air or ins tal lati o n an d w in do ws m ay ne ed to be ins ta lled o r re pa ire dto e s ta b lis h g o o d v e n til a tio n. Cr o s s v e nt ila t ion an d s uff icie nt m o ve m e n t o f a ir in a b u ild ing w ith wa ll m o sa ics is mo st im po r ta n t in p re ve n tin g

de ter ior atio n from m oi stu re pro ble m s.D et e rio ra ted p las ter su pp o rt s m ay ne ed to

b e c o n s ol id a te d be for e a n y c le a n in g c a n b e c o n -s ide re d. D e sic ca ted an d c ru mb ly pla ste rs ca no ft e n b e st r en g t h e n e d b y a p p lic a ti o n o f li m e

5 7



I A IV

a & IA

*

F ig . 11 - P la s te rin g in th e c ra m p in a w al l m o s a ic . B ra c e sa re ap p ly in g li gh t p re s su re to th e m os a ic in an a re a w h e re t h in n e d lim e p la s te r h a s b e e n in je c te d

F ig . 1 2 - R e p la c in g th e c u b e s th a t h a d b e e n r e m o v e d fo r • in s ta lla tio n o f th e c ra m p

w a t e r o r a lm o s t l iq u id li m e p u t ty b y in je c t io n a n d b ru s h in g . S u c h .a p p lic a tio n o f th in lim e p u tty re c o n s titu te s th e p la s te r s e ttin g b y , c re a tin g n e w c ry s ta ls o f c a lc ite to re in fo rc e t h e w e a k e n e d e le -m e n ts o f t h e o ld p la st e r. T h is ap p lic a tio n o f t h in lim e in je c tio n s m a y n e e d to b e a c c o m p a n ie d b y g e n t le p r e s s u r e o n t h e m o s a ic s u r fa c e u s in g p a d s a n d b ra c e s u n til th e p u tty h a s p a r tia lly s e tF ig . 1 1 ) .

C le a v a g e b e tw e e n t h e w a ll a n d p la s t e r o r b e tw e e n la y e rs o f p la s te r m a y b e re m e d ie d b y p la s te r in je c tio n s b u t a m o re s e c u re re a tta c h -m e n t i s o b ta in e d b y in s ta llin g c ra m p s th a t e x -t e n d in t o t h e m a s o n r y w it h w in g s t h a t lie ju s tb e lo w th e m o s a ic c u b e s . I n o rd e r to in s ta ll s u c h c ra m p s a f e w te s s e ra e a re r e m o v e d a n d p la c e d in a m a tr ix .o f a m a te r ia l s u c h a s p la s tic e n e s o th e y c a n b e r e p la c e d in th e o r ig in a l p o s it io n s a ft e r t h e c r a m p is in p la c e . T h e s m a ll a r e a o f p la s te r e x p o s e d b y re m o v a l o f a b o u t s ix o r e ig h tc u b e s is t h e n d r ill e d w ith a h a n d , d ri ll a n d b it t o a d e p t h o f a b o u t f iv e c e n t im e t r e s in t o t h e m a s o n r y w a ll. A c r a m p is t h e n m a n u fa c tu r e d fro m h e a v y c o p p e r o r s ta in le s s s te e l o r m o n e l m e ta l a b o u t t h re e o r f o u r m m th ic k ; i t is m a d e to it t h e d ri lle d o p e n in g e x te n d in g in to th e m a -s o n ry a n d w ith w in g s o v e rla p p in g th e rr ic c io p la s te r (F ig s. 7 - 1 0 ) .

T h e d r ille d h o le is f ille d w ith p la s te r a n d th e c ra m p is in s e rt e d in to t h e w e t p la s te r u n til th e w in g s r e s t o n th e r r ic ci o p la s te r (F ig . 1 1 ). A fte r

the p la s te r a ro u n d t h e c ra m p h a s s e t t h e c u b e sth a t w e re r e m o v e d to p re p a re th e d rill h o le a re re s e t in ne w p la s te r ( F ig . 1 2 ) .

If a re a s o f p la s te r a re lo o s e f ro m th e m a s o n -r y o r if t h e re a r e a r e a s o f i n t e r la y e r c le a v a g e b e tw e e n la y e rs o f p la s te r , in je c tio n s o f th in n e d lim e p u tty o f t h e c o n s is te n c y o f c re a m m a y b e m a d e w ith a s y ri n g e t h r o u g h t h e d r il le d h o le b e fo re in s e rtio n o f th e c ra m p .

T h e m o s a ic s u rfa c e is b ra c e d w ith m ild p re s -s u re t o a s s u re g o o d c o n ta c t b e tw e e n t h e c le a v -a g e a re a s w h il e th e li m e p u t t y i s s e tt in g ( F ig . 1 1 ). T h e c o m b in a tio n

o f c ra m p s a n d p la s te r in je c -t io n s h a s b e e n u s e d s u c c e s s fu lly b y t h e c o n -s e rv a to rs o f th e B y z a n tin e In s titu te o f A m e ric a o n s e v e ra l w a ll m o s a ic s in B y z a n tin e m o n u m e n tsin Is ta n b u l, C y p ru s a n d M o u n t S in a i.

T h e in s ta lla tio n o f c ra m p s g o e s h a n d in h a n d w ith c le a n in g a n d c o n s o lid a tio n o f s u rfa c e s . F re -q u e n tly m o s a ic s u rfa c e s h a v e b e e n c o v e re d in p a r t o r to ta lly b y a p p lic a tio n s o f w h ite w a s h o r p a in t a n d /o r p la s t e r. A ll r e p r e s e n t a ti o n a l m o -s a ic s in B y z a n tin e m o n u m e n ts in Is ta n b u l w e re w h it e w a s h e d o r p a in t e d o r p la s t e re d o v e r a t v a rio u s p e rio d s w h e n th e b u ild in g s w e re i n u s e a s m o s q u e s T h e la y e rs o

f p la s te r c o v e rin g th e te s s e ra e w e re s c ra p e d a w a y to e x p o s e a n a re a fo r c ra m p in s ta lla tio n w h e re n e c e s sa ry . E a c h c u -b e w a s c le a n e d in d iv id u a lly a s w e ll a s t h e in te r-s tic e s b e tw e e n c u b e s u s in g d e n ta l to o ls , o ra n g e w o o d s ti c k s , a n d to o t h b r u s h e s w ith a l it t le

8



F ig 1 3 - Po rtr a it o f t h e B y z an t in e E m p e r o r A lex an d e r

tes ser ae. G iorn ati jo in s c a n b e s e e n a lo n g

in S t. So ph ia. T h e b a ck gr o un d i s a

t he lef t si de of the fig ur em ixtu re of go ld a nd sil ver

w a te r. L a rg e a m o u n ts o f w a te r m us t b e a v o id e d as it so fte ns th e s e ttin g b e d . E a ch lo os e c ub ew a s re m o v e d a nd re s e t w ith fre sh p la s te r. W h e re c u b es w er e m is s in g t h e ex po se d p ai n te d s et tin g b e d w o u ld b e c a re fu lly c le a n e d b y m e c h a n ic a lp roc ed ur e s an d o fte n th e c le a n e d p a in te d s u r-fa c e w o u ld co m p le te t h e c o m po si tio n ( F ig . 3 -4) . W h er e s m a ll are as o f se tti n g be d w e re los t w ith ina m os ai c s ur fac e, th e l o s s e s w e r e fill e d w ith

lim e p la s te r m ix e d w ith m a rb le d u s t o r s ifte d o ld p la st e r - o ne p ar t li m e to t w o o r th re e pa rts

in e r t. T h e E m p e ro r A le xa n d e r p o r t ra it i n S t.

S o ph ia (Fi g 1 3) is an ex am p le of a m o s a ic t ha t

w a s p a in te d o ve r a n d so cl e a n e d a n d co n s o lid at -ed . T hi s m o sa ic i s o f p ar tic ula r i nte re st in tha t

gio rn a ti ca n b e ob se rve d to s o m e e x te nt in the

s e tting p las te r - the h e a d a nd u p p e r b u s t w e re s et in on e d ay , i n s c rip tio ns in o n e da y, an d t he u p p e r to rs o in a n o th er da y. O n e ca n o b s e rve w h e re o n e d a y o f p la s te r jo in s t h a t o f a n o the r. T h is m o s a ic is a ls o n ot e w or thy b e c a u s e o f t h e lar g e nu mb er of sil ve r c u be s in the ba ck gr o u n d -no d o u bt to ref lec t l igh t f rom t he d iml y l it a re aw h e r e t h is fi g u r e is lo c a t ed - h ig h up o n t he

no rth -w es t p ie r s up po rti n g th e g re at do m e o f

S t. S o p h ia .T h e co n s o lid a tio n o f t h e De is is p an el of th e so ut h g al le ry o f S t. S op hi a i s w el l de sc rib e d an dillu st ra ted in a pu bli ca tio n o f t he B y za nt ine In -s titu te ( 2 ). T h e p la st e r c o v e r in g a pp lie d b y t h e Fc sa tis in th e m id -1 9t h c en tu ry wa s r em o ve d,

c ram p s in st a lle d a n d e dg es re att a c h ed w ith ne w p las te r . H ol e s we re fil led w ith pl a st e r a n d t o n e d w it h n e u t r al gr e y to n e s . N o n e w c u b e s w e r e in s e rt e d .

In t h e la rge D e is is pa n e l o f th e K a riy e D ja m i lar g e ar e a s o f m o s ai c c ub es w e re m is s in g a nd te a tm e n t o f lac un ae p o s e d a d iffic u lt pr o b lem (F ig. 14 . 1 6) : M uc h p a inte d se ttin g b e d w as re -v e a le d in c lu d in g s o m e n e w in s c rip tio n s ( 3 ). T h e p ain te d s e t tin g b e d s ug ge st ed p r oc ed ur e for

fillin g lar g e los se s. Th es e a re as w e re p las ter ed w ith li m e p las te r a n d sm oo th e d to a fla t su rfa ce (F ig. 14 ). Th es e fla t a rea s w e re th en te xtu re dw ith a s m a ll c h ise l to re se m b le a rea s o f o rig in a lse tti n g be d a nd to ne d w ith w at e r- c ol o u r (F ig . 1 5 ).

W h er e la rg e r los se s e xi s te d , w a ter -co lo u r tin ting c o n n e c te d e x ist in g p a tc h e s o f c ol o u red s e tt ing b ed to c o m pl e te a la r ge p or t io n o f t h e de si g n

(F ig. 16 ). N o th ing n e w w a s in v e n te d. N o n ew cu be s w e re ins e rte d a n d a re as o f c o m p le te lo s sw er e t int ed in a fla t t on e wi t h no a t te m p t a trec on st ruc tio n o f m is s in g p a rts .

A fra g m e n t o f a 4 th c. A .D . w a ll m o s a ic fr o m th e G re a t S y n a g o g u e of S a rd is i s illu s tra te d in F ig . 1 7 . Th e p la st e r is in t hr e e la y e r s - a p ink

p la s ter o v er th e b ric k w a ll a b o u t o n e t o o ne a n d

o ne -h a lf cm . thi c k. T h e in ter m e di a te p las te r is ab ou t th re e c m . th ic k a nd co ns is ts o f a m ix tur e of lim e, sa nd an d s tra w . T h e se ttin g b ed is ab ou ton e a nd o n e -ha lf c m . th ic k a nd is co m po se d o flim e a n d m a rb le d us t. T h e c ub e s o f g las s a n d

9



F ig. 1 4 - De tail of t he D ei s is mo s aic of the Ka riye Dj a m i,Is tan b u l, du rin g c le an ing an d c o ns o lid a tio n. A n e w in s c rip tio n ha s b e e n fo u nd in t he p a in te d p la s te r w h er e c u be s h a v e fa ll en . H o le s h a ve b e e n fi lle d w ith l im e p la s te r

Fi g. 1 5 - He ad of Ch r ist of t he De isis af t er trea tm ent

F ig . 16 - T h e D e is is o f t h e K ar iy e D ja m i sh o w in g m e th o dfo r t re a ting l ac u na e

F ig . 1 7 - D r aw in g o f a fr ag m e n t o f a wa ll m os a ic f ro m th e S yn a go g ue of S a rd is , Tu rke y , s h ow ing co n -s tr uc tion te c hn iq u e

F ig . 1 8 - S am pl es p rep a re d a s a d e m o n st ra tion of w a ll m o s a ic te ch n iq u e . Th e b ric k o n t h e l ef t is c ov e re d w ith the fir s t tw o lay er s o f pl a st e r.The ce nte r br ick h as be e n p ain ted in t rue fre s co a n d a fe w c ub e s h av e b e en se t. T he bric k o nth e r ig ht i s c om p le t ed an d r e qu ire d o n e h ou r to se t th e c u be s in th e p a int e d in ton a co

n a t ur a l s to ne ar e s et in the p ain te d s ur fac es o m e w h a t s pa c e d to re v e a l a re a s o f th e p a in te dp la s te r . T h e f ra g m e n t is p a r t o f a d e d ic a t o ry in s cr ipti on fro m the fo rec our t o f th e S yn ag og u e.

W h ile at Sa rd is t h e au tho r p re p a r ed so m e s m a ll d em on st r at ion w all m os aic s o n b ri c ks to illu str ate th e t ec hn iqu es us ed in th e S yn a-g og ue (F ig. 18 ) . T he se tti n g o f th e cu b e s in th e pl a st er of o n e b ric k to ok th e a ut h o r o n e ho ur. At th a t r at e it is es tim at e d th a t it w ou ld tak e40 h o ur s t o s e t o n e s q u a re m e tr e . P e rha p s a s kil led m o sa ic wo rk e r c ou ld se t b e tw ee n o ne

6



ha lf t o o ne s q u a re m et re in a d a y - n ot co un tin gt im e fo r p re p a ra t io n o f t h e w a ll a n d s e tt in g

p la s te r .T h e a bo ve i s a b rie f d es cr ipt ion o f t rea t-

me nt of w all m os a ic s a s pra ct ise d by th e c on -

s er v a tor s o f t h e By za nt ine In sti tut e o f A m eri c a .

O b v iou sly m an y d e tai ls o f p ro c e d u re a n d t e c h -

n iqu e a re o m itte d in s uc h a c ur s o ry re p o r t. N o w ri tte n r ep or t c an ad eq ua te ly su mm a riz e p ro -

c e d ur e s in or d e r th at th ey ca n be fo llo we d b y a n o th e r w itho u t s u p e rvi s io n .

No tes

1 V it r uv ius , T en Bo o ks on Ar c hit ect u re N ew Y o rk, Do ve r, 196 0, VII , p. 20 4 ff .

2 T . W h it te m o r e, T he M o sa ics of H a g hia S o ph ia in I s tan -bu l F ou rth Pr elim in ary R ep o rt O x fo r d , U ni v er s ity

P re s s, 195 2.3 P . U n d e rw o o d , Th e K ar iye Dja mi v. 1 & 2 , B o lli n ge n

S e ri es LX X , N e w Y o rk , P a n th e o n, 1 9 6 6.

DI SC US SI O N

T h e s e n ot e s d o n ot at t em p t t o r e p r o d u c e w or d f or wo rd th e m a ny co m me nt s a nd q ue s-s tio n s . W e h a ve , h ow e v e r , t r ie d t o r e c o rd t h e e ss e n tia l po in ts, thu s s h o w ing th e g en er a l d ire c-tio n o f t h e d isc u s s io n w h ich fo llo w e d th e le c tu re of M r. M a jew s k i.

M m e . A n d ree sc u: A m I rig ht . s e e m to n ot ice

a ce rta in loo se ne s s in th e t e xt u re ? S o m e o f th es p a c e s b etw e e n th e t e ss er ae ar e w h ite .

M r. M a je w sk i: I t c o u ld b e th a t the tr e a tm e n t h a s n ot be en fi n is h e d .

M m e. A n d re e s c u : I s i t th e s e t tin g b e d w e

s ee be tw ee n the te ss era e?

M r. M aj e w s k i: T h a t 's po s s ibl e . P ro ba bl y t h e y h a v e n 't f in is h e d w o rk in g o n i t.

M m e . A nd re e s c u : H o w d o y o u pu t t h e cr a m -po ns in ?

M r. Ma je ws ki: T h e y're p ut in wh ile w or kin gon th e s u r fa c e .

M m e . A n d re es cu : D id yo u a n d E rn es t H aw -ki n s yo ur se lve s c ho o s e th is m e th o d of re c o n -s tru ct in g th e m o sa ic fo u n d a tio n s ? U p to wh at p oi n t ha ve yo u re m a in ed fa ith fu l t o t he s ur-

v iv ing t rac es o f th e o ri g in al w o rk - o r, in ot h e rw o rd s , s om e o f th es e line s w e s e e , h a v e t h e y b e e n dr a w n b y y o u ?

M r. M aje w sk i: I f y ou 'r e s pe a kin g of th e

C h ri s t o f t h e D e e s is , w e h a v e t he re s p e c if ic

p o in t s b e t w e e n w h ic h w e h av e d r a w n s o m e ,.

lin e s .

S ig . T or rac a: Th e c ra m p o n s , a re the y s et in m o rta r?

M r. M a je w s k i: Y es , e xc ep t in t he c a s e o f

sm a ll s u rfa c e s w h e re p la s te r o f P a ris w a s u s e d .

6



THE RESTORATION OF MOSAICS IN GERMANY

The first German mosaics were discovered

in the second half of the 19th century at Trier.At that time lifting procedures were not yetdeveloped; trained restorers did not exist, butrather manual workers were employed in varioustasks in the museums then being founded. Itmight have been a guard, for example, whoglued together scattered bits of ceramics, orwho made the excavations. Detaching and re-storing mosaics was also considered a part ofhis job. Considering the lack of technical meansand know-how at their disposal, these peoplesucceeded rather well. In breaking up the mo-saics, the motifs were preserved but it was im-

possible to save the surrounding decoration.These broke by themselves when the motifswere chiselled out. Wooden braces were putaround the fragments, and thanks to these, itwas possible to remove the sections intact withthe mortar, which was 12-20 cm. thick. The frag-ments were taken in this form to the museumfor display. Considering the weight of the com-bined mosaic and mortar, it was necessary toform very small fragments and thus the loss oforiginal work was immense.

At the turn of the century, the technique ofgluing mosaics was begun in Germany, havingoriginated in Italy. Bone-base glue was used,but it was still necessary to work with smallfragments because ground humidity preventedthe glue from adhering satisfactorily, and scien-tific means to dry large surfaces were not avail-able. (This problem was less acute in Italy dueto the dry summers). The mosaics were driedwith alcohol or an acetylene torch; but as theglue was very sensitive to infiltrations of water,one could not glue and remove smaller or largerparts of a mosaic without the loss of one or tworows of tesserae at a time to delineate thesefragments. Using a long, thin chisel the mortarwas split between two layers which permittedthe lifting of the mosaic; this method proved tobe satisfactory as long as the mosaics were

relatively small. If they were large, the difficul-ties persisted as it was nearly impossible toinsert the chisel under the surface of the mosaic,

by Rolf Wihr

Translated from the Frenchby Patricia Bonicatti

and still stay between the two layers. In effect,

small irregularities in the mosaic or the littlepebbles which were lodged between the twolayers of mortar caused the chisel to slip down-wards or, even worse, upwards. There was there-fore a great risk of piercing the mosaic. Theexcavated fragments were still extremely heavyand it was necessary to remove the mortar com-pletely in the workshop with hammer and chisel.Sometimes, due to the hardness of the mortar,there was also a danger of splitting the cubes.

This was the technique I encountered whenl began working as a young restorer. After awhile, I was able to replace the bone-base glue

with polyvinyl acetate diluted in ethylacetate(known under the brand name Mowilith 35/73 -Farbwerke Hoechst, Frankfurt-Hoechst, W. Ger-many). This glue was not soluble in water, butit was still necessary that the surfaces beabsolutely dry in order to adhere sufficientlyand to avoid water infiltrations which mightseparate the glue from the mosaic before de-tachment. In order to avoid this risk and to per-mit the removal of larger sections, we began todry large surfaces using 2,000 watt infra-redlamps. Even though the problems of drying werethus partly resolved, those of the hard mortar,

of the uneven surface of the mosaic, and of thesmall pebbles between the two layers of mortarremained just as acute. Also the detached frag-ments were still very heavy and it was veryoften impossible to avoid splitting the originalmaterial without cutting it with an electric saw,following the Bassier method". At that time,we were unable to saw the mortar as we hadneither the technical means to carry out the worknor any means of preventing accidents. Theseproblems led us to seek a new method.

While on a trip to Italy in 1951, I saw frescoesat the Central Restoration Institute, then underthe direction of Professor Vermehren, which hadbeen detached from a wall by being rolled off.Several years later, Stefano Locati used the samemethod on the mosaic of Dionysos at Cologne,after we had met at Trier. However, it was stillimpossible for me to remove a mosaic with this

62



Fig. 1 - Storage area with hanging mosaics (bedding made

of Araldite D, hardener HY 956 and 200 % sand,reinforced with fibreglass

Fig. 2 - Removal of a mosaic with a cylinder

method at Trier, because of the traditional na-ture of the work there. So I was obliged to waitfor another occasion. During this period, I wasable to make progress in the technique of layingmosaics. We had in our museum several hun-

dred square metres of mosaics still glued tocotton cloth, or others which were already setin plaster or cement, and kept in storage. Itwas necessary to arrange them so that eachfragment might be visible without wasting timeor labour. It was also necessary to assemble thefragments of the central motif. I resolved thisproblem by creating a fine bed of Araldite D,adding 200 /0 of sand and 15 % of HardenerHY 956 to it and reinforcing it with fibreglass.Next the beddings were hung on a rail: thismade it easy to handle the fragments by slidingthem along the rail, thus allowing assemblage

of the principle design. This took me years toaccomplish (Fig. 1).

At last I had the opportunity for which I hadwaited ten years A hundred years earlier ,exca-vations had been made in the Trier region, wherea Roman villa had been discovered. Five roomswere paved with mosaics. As they could not bedetached at the time, it was decided to leavethem in situ protecting them from the elementsby small sheds. A hundred years later (WorldWar II also doing its share of damage), the mo-saics had clearly deteriorated. Some of themhad a hollow ring; they bulged and threatenedto crumble at the first touch. Other pieces hadalready disappeared and the damage increaseddaily. It was urgent to solve the problem by de-tachment of the mosaics. The original Roman

mortar had to be removed and replaced by mo-dern mortar. Naturally we had to detach themin the traditional way, which we did for the firstfour. It was obvious that much of the originalmaterial would be lost, and we also knew that

after the detachment the real work would begin:transporting them into the workshop, removingthe mortar, laying the cleaned mosaics in plasteras we had always done, ungluing the cottoncloth, filling in the holes, assembling the frag-ments and covering up the chisel marks, re-se-parating the fragments, transporting them andreplacing them in their original locations, aswell as repairing the damage done to them dur-ing restoration.

I was given permission to proceed accordingto my own method with just one of these mo-saics (the smallest one, which measured 2 x 4

m). As all the mosaics had been kept sheltered,they were not particularly damp and so I tookthe risk of gluing mine in one piece. It was tobe replaced in its original location. These twofactors were important for the success of mymethod.

We built three wooden discs, each 90 cm iindiameter and 2 cm thick. In the center of eachdisc we made a hole. We spaced the three discsso that there was 1.5 m between them. Then weformed a drum by juxtaposing slats of wood 5 cmwide and 2 cm thick and attaching them to thediscs. This cylinder was light in weight and

could be assembled and dismantled easily. Themosaic was glued, in one piece, with Mowilith3 5 / 7 3 to cotton cloth. After it dried we install-ed the rolling wooden drum on the 3 m side ofthe mosaic, which we then began to split directlybetween the cubes and the mortar. The separa-tion proved no problem even where the mortarwas very hard (Fig. 2). Rather than removing it,we left the modern concrete from the previous

6



c e n tu ry 's re s to ra t io n w h ic h w a s 2 c m th ic k , o n th e ro lle d m o s a ic . A ft e r tw o h o u rs a n d t w o tu rn s o f the d rum , t h e 12 m p av em e n t w a s c om pl e te lyr o ll e d u p. W e p la ce d a s te el ro d in t he h o le t hr o u g h th e e n t ire c y lin de r, an d o n e a c h e nd w e a dd ed a ne w w o o d e n d is c a littl e l a rg e

r t h a n th e o ri g in a l o n e s . W e ins ta lle d s c re w s i n o rd e rto f a s te n th e t w o d is c s o n e a ch e n d . W e w ra p p -ed v ery s tro n g pa pe r a ro un d t h e m o s a ic on th ecy lin d e r a n d se cu red it w ith ro p e s .

A fte r t h a t w e w e re a b le t o r o ll it aw a y .A lm o s t a y e a r w e n t b y b e fo re w e a p p lie d a

la y e r o f r e in fo rc e d c o n c re te an d a n in s u lat ion a ga in s t s oi l d a m pn es s . D u rin g thi s t im e w e re-s to re d th e fo u r o th e r m o s a ic s in th e tr a d it io n a l w ay . F o u r a n d s om e tim es s ix m e n w e re bu sy a ll y e a r lo n g d o in g th is w o rk . In th e m e a n t im e .I w a s bu sy w ith o t he r p ro je c ts . A t t he e n d o f the y e a r w a n te d t o re p la ce th e m o sa ic i n the s a m e w a y in w h ic h it h a d b e e n ro lle d u p . W e p lac ed th e cy lind er in th e s a m e p o s itio n, the n w e a dd ed o n t he to p o f t h e re inf o rc ed co nc re tean o the r i n s u la tin g l ay e r to the c em en t m o rta r,3 c m t h ic k . T o m a k e th e m o r ta r ad he re a n d t o ins ur e it s f le x ib ili t y, I o rd e r e d th e a d d it ion o f 1 0 % di s pe rs ion o f M ow ilith. Th an ks to th e two larg er te rm ina l d is c s, th e c yli nd er did n ot tou ch th e fre sh m or tar . W e wo rk e d on a sm a ll b rid ge s p a n n ing th e m o sa ic w h ich a llo w e d u s to lev el a n d at tac h t he m o sa ic to the fr es h m o rta r e a si ly. T wo ho ur s l ate r ( inc lu d in g t he pr ep ar a to r w or k)t h e jo b w a s f in is h e d . W e ro lle d t h e c y lin d e r a s id e a n d l e t th e m or tar dr y . T h re e d ay s la te r, w e d e ta c h e d t he c lo t h w h ic h h a d b e en g lu e d w ith M o w ilit h . Th is wa s n o t d iffi cu lt a s, in th eme an tim e , a lo t o f d am p ne ss h a d ris en fr om t h e s oi l a n d ha d un gl u e d t he c lot h f ro m t h e m os a ic .

A fte r rep lac em e n t o n the g rou nd , o ur m o sa ic s ho w e d so m e im p e rfe c tio n : a t the p o in t w h e re w e ha d b eg un to u n ro ll t h e m o s a ic it s an k a b o u t o n e c e n tim et re. In ef fec t , its w e ig h t h ad c a u s e d t he fr es h m o rt a r to s lip an d th e r e w a s n o t e no u g h m o rt a r th e re to k e e p it le ve l. Fu rth er -m o re , it d id n o t a d h e re a s w e ll a s I h a d h o p e d an d I r e a li ze d t ha t th e m a n w h o p r ep ar e d th e m o rta r h a d ig n o red m y o rd e rs a n d h a d n o t a d d e d th e 1 0 % dis pe rs ion (t o i mp ro ve th e a d h e s io nof the m or tar ) . H e ha d a dd ed a pro du ct to liq uif y th e m o rt a r , an d the re su lt w a s e x a c tly t h e o p p o -s ite to th at wh ic h I ha d int e n d e d . H o we ve r, the te ch ni q u e w hi c h I u s e d m a y b e c on si d e re d s u c-ce ss fu l in sp ite o f th e s e s m a ll d ra w b a c ks .

A t th a t t im e, th e c o s t o f tr a d it io n a l r e s to r a -tion p er squ ar e m e tre of m osa ic ca me to e xa c tly 1 ,2 0 0 D e u ts c h m a rk s . T h e r e s tor a tio n co st p e r s qu ar e m e tre us in g t h e ne w m e th o d wa s a b o u t 1 1 0 D e u ts c h m a rk s : le s s th a n o n e -t e n th a s e x -p en s iv

e. P e rh a p s w e c o u ld im pr ov e t he te ch n iq ue o f rol ling a n d u n rol lin g th e m o sa ics , u s in g a m ix tu re o f A ra ldit e a nd sa nd a s a m ort ar be dd ing . I n th is c as e, it w o u ld be n e c e s s ar y t o u ng lu e t h e clo th

w ith s o lv e n t. T he b e d d in g m o rt a r w o u ld b e s ligh t-ly m o r e e x p e n s ive , b u t th is w o u ld b e a m in o rd isa d v a n tag e c om p are d to the e co n o m y o f th ism eth od as a ga ins t t he tra di tion al on e.

S e ve ra l w ee ks la ter an ot he r m o s ai c , 6 0 m , wa s d is c o v e red a t B a d -K reu

zn ac h . It w a s s u m -m e r ti m e , b u t i n G e rm a n y i t ra in s m o r e d u r in g t h a t s e a s o n t h a n i n I t al y s o w e e re c t e d a te nt to p ro te c t t h e m o sa ic . In itia lly w e b e g a n t o d ry th e firs t p a rt w ith inf rare d la m p s ; th e n w e g lu e d a nd re mo ve d it a cc ord in g t o t he tra di tion al m e-th o d . T h e m o rta r o f t h e m o s a ic w a s e x tre m e ly h a rd a n d s o w e m a d e v e ry s lo w p ro g re s s . W e c o u ld o n ly d ig u p v e ry s m a ll p a rt s a t a tim e a s d a m p n e s s ro s e ra p id ly fr o m th e g ro u n d . O n c e a g a in , w e l os t a g r e a t d e a l o f t he o r ig ina l m a -t e r ia l d u e to th e h a r dn es s o f t he m o rt a r . T h is m o s a ic w a s u n lik e t h o s e u s u a lly f o u n d i n G e r-m a n y (w hic h a re g e n e ra lly co m po s e d o f g eo m -etr ic m o tif s ) a n d m or e like th os e fou nd in N o rt h A fr ica w ith el em en ts fo rm ing a sc e n e , s o it h ad to be b rok en up in to la rge se ct ion s. A t t he s a m etim e , it w a s imp er at ive th a t the m os ai c b e a b le to p a ss th ro u g h th e m u s e u m d o o rs a nd th e re fo re w e h ad t o d ivi d e it int o s ec tio ns o f 2 x 2 m o r2 x 3 m an d ro ll t h e m u p .

A d eta ch m e n t p lan w a s es tab lis he d: we d e-c id e d to d iv id e th e m o s a ic in to s e c tio n s a n d d ry th em w it h o u r la rg e inf r a- re d l a m p s . A s th em o s a ic w a s v e ry d a m p , w e c o u ld o n ly d ry , g lu ean d r oll up 4- 5 m e a c h d a y o n o u r c y lin d e r . A tf ir s t, w e s e p a r a te d t he m o s a ic t e s s e r a e f r om t h e ir s u p p o rt b y ha n d a n d la t e r c o n t in u e d t h e w o r k wi t h a s m a ll pn eu m at ic h a m m e r , w h ich s a v ed a gr ••e at de al of tim e an d e ffo rt (F ig. 3) .

F ig . 3 - S e p a ra tion of t he te ss e ra e w ith a sm all p n e um at ic ha mm er

On ce de ta c he d, th e s ec tio ns we re pr og res siv ely ro lle d o nt o t h e dr u m . T h a n k s to th is w e co u ld a lw a y s s e e e x a c tly w he re to p la c e t h e p n e u m a -t ic ha m m e r t o s ep a r at e t h e te s s e ra e fro m th e m o rta r. T h e s ep ar a tio n of th e g lu e d fra gm e n ts

6 4



Fig 4 • A glued piece of mosaic, ready to be separatedAt the end, a glued strip of cotton at the edgesof adjacent sections

5 - A section of mosaic has been rolled. On theother side it has been pulled onto a board

Fig. 6 - Cleaning of the tesserae with an ultrasonichammer

Fig. 7 - The reverse side of a mosaic, cleaned by anultrasonic chisel. The design on its other sideis clearly visible

from the mosaic still remaining in place wasno problem. We proceeded as follows: on theedges of adjacent sections which were not yetbeing removed, we glued another strip of cloth5 cm wide from top to bottom at the level of

the demarcation line (Fig. 4). Then, over the cloth

strips, we placed straight pieces of wood ormetal which served two purposes: they actedas a support for rolling the cylinder on top of

the mosaic, and as a protection against splittingthe fragments along the demarcation line. Usingthis method, we could work without loss oforiginal material (Fig. 5). The sections which

we separated from the rest of the mosaic wereonly rolled a half turn of the cylinder, and onthe other side we gently pulled the section tospread it out flat. Having positioned the mosaic

face down and revel, we were still able to dis-tinguish the different scenes from the back andproceeded to cut up the mosaic, piece by piece.

65



Fig. 8 - Honeycomb support being placed on the reverseside of a section of mosaic

with a knife, without losing any of the originalmaterial.

We loaded the sections onto a truck andtransported them to our workshops where theywere remounted. Since then, they have been

waiting to be restored. Before leaving Trier, I wasable to direct the continuation of the restora-tion: cleaning the back of the mosaic whereverit proved necessary with an ultrasonic chisel of22 or 44 KHz (Ultrachall GmGh. D6148 Heppen-heim) as is done in restoring frescoes (Fig. 6-7)and laying the pieces in Araldite on a honey-comb structure of aluminium (Aeroweb - CIGA-Geigy, Basel, Switzerland), following the methoddevised by Claude Bassier (Fig. 8).

I foresee great possibilities in improving thetechnique of detaching and restoring ancientmosaics, in their removal, rolling and unrolling

without loss of original material and in cuttingtheir reverse side, in their cleaning with ultra-sonic chisels, and in their relaying in Aralditeon honeycomb aluminium structures.

I hope that I have been able to give yousome useful suggestions, and I thank you foryour attention.

The discussion which followed this lecturewill be found on page 81.

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SO M E PR OB LE M S IN T HE CO NS ER VA TIO N O F M O S AI C S

Fir s t o f a ll, I w o u ld like to tha nk D r. Fe i de n,IC CR O M , a nd al l its m e m b e rs fo r th e ir c o rd ia l h o sp ital ity. M o s t e sp e cia lly I w o ul d lik e t o th a n k m y fr ie n d G a e l d e G ui c he n f o r h is in it ia tiv e i n

o rga niz ing this sy mp osi um . Th an ks to h im , we a re g ath ere d t o da y t o st u dy th e pr obl e m s p o se d b y t he con ser vat ion of m os aic s.

Th e a rea wh ich w as for m e rly the an cie nt

Ro ma n w orl d is ric h in m osa ic p av em ent s, b utpo or i n c on s er v at ion tec h n ic ia n s. Fo r th is re a -so n , a t th e in sti g at ion o f M . C ha b er t (th en Dir ec-to r of th e F re n c h A n ti qu itie s S e r v ice ) , w e s e t

u p a pri v ate co ns e rv a tio n s tud io t o w ork ex c lu -s ive ly for t he st a te . Fo r th e p as t 1 2 y e ar s o u r

m a in ac tivi ty h a s co n s ist e d in s a vi n g, c on s e rv in g a nd tre atin g m os aic s an d m ur al p ain ting s.

W h er e c o ns e rv a tio n is co n c e rn e d, o ne m u st a u to m a ti c al ly d e a l wi t h d et e rio r at ion an d d e -

s tr u c tio n . E v e ry m om e n t o f t h ei r liv e s , fro m

c re a tion to f in a l d e st ru c tion , m o s ai c p av e m e n ts ar e s ubj ect to a n e vo luti ona ry pro ces s o f d e te -rior a tio n . O n e c an sp e a k of " co n s e rv a tio n " on lyf r om th is p er s pe cti v e.

T h e c on s e rv at io n o f m os a ic s is b a s ica lly c on -d it io n e d b y s oc io -e co n om ic a n d s o ci o -c u ltu ral fac tors . In Fr an c e, the se fac tors ef fec t pr oce s-se s w h ich ar e p a rti c ul a rly de trim en tal to m os a ic c on s er v ati o n:

1 . M or e t h an 90 0/0 o f th e m o s a ic s br o u g ht to l igh t a re d es tro y ed .

2. Ver y fe w mo sai c s a re con se rve d in s i tu

of tho se so co n se rve d, a ll a re i n a s ta te of a d -va nce d a nd irre ver sib le d ete rior atio n.

3. A m o n g the mo sa ics rem ov e d a nd tr a ns -fer r ed ov e r th e pa s t c en t ur y , m or e th an 90 0

h a ve su ffe re d g ra v e d e te rior a tio n o r h a ve b e e n los t.

Th u s , st a tis tica lly s pe a k in g, t he fie ld o f c o n -s er va tio n a s a te c hn iq u e t ou c he s o n ly a t in y p er -

c ent age of the m osa ics dis cov ere d.T h e a d m ini s tra t io n s in c h a rg e m u st b e i n-

fo rm e d o f t h e rea l pr obl em s an d s triv e t o u nify th eir eff o rts th rou g h e xte ns ive stu d y o f t h e fac -t o rs wh ich ar e re sp o ns ibl e fo r th is s ta t e o f a f-

b y C lau d e B as s ie r

Tr a ns late d f rom th e F ren c hby Ala n B on ica tti

fa irs . A n y e ffe c tiv e a c tio n m us t le a d to c h a n ge s in p res e n t l eg isl at io n , a d m ini st ra th ie st ru c tu re s ,a nd inte rve ntio n p roc ess es .

T e c h ni c al c on s e rv a tion int e rv e nt io n s , w h ic h ar e th e o n ly o n e s w ith w h ich w e a re c o n ce rne d h er e, m u s t a lw a ys be se en in t his co nte xt o r

th e y w il l en t ire ly l o se th e ir s ig n ifi c an ce .

Co ns e rv a tio n i s no t th e a pp lica tion of a c ol-le cti o n o f r e ci p es of pro ce d ur es. It i s fo un d ed

o n th e e x pe rie n ce p ro v id e d b y o ur p re d ec e s so rsa n d co lle a gu e s , on sy s te m a tic c rit ic is m o f o u ro wn w ork , on h isto ric a l r ese arc h a nd on th e

n at u ra l sc ien c es .Ev ery co nse rva tio n o p er a tio n m us t be ba sed

u po n t he c o llec tion an d int eg rat io n o f th re e k in d sof info rm atio n:

1 . C o m p le t e k no w le dg e o f t he na t ur e a n d

str u ct u re of m o s ai c s a nd ea ch of t he ir c o ns ti-

tu e nt p ar ts.2 . T ho rou g h k no w le d g e o f th e ca u s e o f d e te -

r ior a tio n, e vo lut ion a ry pro ce s se s, o r t h re a ts ofd es truc tio n .

3. Th e f u tu re p la c e m e n t a n d r ol e o f t h e m o -sa ic a fte r ev ent u al co n se rva tion an d r e sto rat ion w o rk . Te stin g o f te ch niq u es an d i n te rve n tio ns.

A ju d g em en t b a se d on th e m o s a ic 's f ut u re

is th e p r in ci pa l fa c to r in d ire ct in g t he pr o ce s se s o f co ns erv atio n or r est ora tio n T his ch oic e is e ffec ted by so c io -ec o no mi c a n d s oc io-c ult u ra l fa c to r s; the se alo ne sh o ul d b e t h e t op ic o f a m ee ting .

Let u s t a ke th e th ree po ints ab ov e :

1 . K n ow le dg e o f st ru c tu re

F rom th e g rou nd up , a mo sai c p a ve me nt isc o m p os e d o f th re e m a jo r s tr at a : a s u p po rt, in te r-m ed iat e la ye rs, a nd th e te sse rae .

— T he ac tua l su ppo rt i ncl u de s:

th e g ro u nd (n atu ral soi l),th e sta tum en o r s u pp ort . — T he int erm ed iate la yer s c ons ist of:

th e r ud u s or fou nd atio n,th e nu cleu s o r b as e .

67



Fig. 6 - T iv oli, a n u n prot e cted mos a ic i n sit u da m age dby w eathe r, mi c ro-o r ganis ms a nd ve geta tion

Fig . 7 - P iazza Arm e rina . an un p rot ec ted m os ai c n s tu

und er goi ng th e s am e cha n ges

F ig . 8 - Loup ian ( H era u lt). a n unp rotec ted m osa ic n s tu

und e rgo in g s im ila r cha n ges . No te a l o cali ze dde s truc ti ve p r oces s

a ge a t the h a nd s of a rch a eo lo gi sts a n d a d m i-nis trato rs. T he form e r a re of ten u nfa m ilia r wi th sim ple p reca utio ns f or im ped ing d ete riora tion; t h e la tter rea c t to o slo wly - if t h ey reac t at all.

M osa ics a re ru ined by the d estr u ctio n o f the s u pp or t, b y th e de te rio ra tio n of th e t es se ra e an dthe j cin ts be twe en th e m, b y d e te rio ra tio n of th e m at e rial in w ic h t h ey a re s et o r of th e b ond be-twe en t h e te sse llate d lay er a n d it s su p por t , an d b y th e d e stru ctio n of the actu al te sse r a la yer.

Th e la tte r c an o cc u r v er y r ap id ly if t he p av em e nt bo rd er o r l ac un a e ar e n o t k e pt in go o d re pa ir .

The orig ins o f th e se d iso rder s are : fir e , hu -m id ity , w a te r-b or ne c he m ica ls in th e at mo s ph er eor the grou nd, plan ts, a nim als, men , an d m a-ch in es . The s e a g en ts pr o vok e di ffere n t st re ss e sw hic h ac t bo th se p ara tely a nd t og et he r.

2 .1. 1. M ec ha ni ca l s tre s s: co m pre s sio n , sh o ck,

etc. Mec han ical stres s pe rpen dicu lar t o the sur -fa c e c au se s ho rizon tal c o mp re ss io n o f the upp e rpa rt o f the sup por t an d tra ctio n in the low e rp a rt. T he s e h o rizo n tal s tre s se s in o ppo s ite d i-r e ctio ns te nd to m ake the lay e rs s lide acr o ss

e a ch o the r; th e y a re lik ely to cr a ck the s upp o rtin its w ea k est poi n t - i . e. th e st ratif ic atio n b e dsin or d er o f fr a gili ty .

W h e n ve rti ca l s tr es s is ap p lie d to a p av e-m en t w he re th e su p po rt h as b ot h st ron g a nd

we a k r e sis t enc e ar eas , the sup por t bu c kle s c ra c ks . b re a ks , o r sin k s Su b ter ra ne a n w ate r

pr o duc e s th e sa m e p hen ome non .

La tere l str e ss h as th e s a me effe c t, bu t in an

e ven mo re p ro no un ce d m an ne r.

2 .1 .2. T herm al s tress : in th e pr e se nc e o f a wa te r v e cto r , th e th e rm a l s tr ess of fr os t pro -vok es s wel ling o f po rous ma teria ls. T ang e ntia ls tr es s es in cl ud e sp lit tin g, fl ak in g a n d sp lin te r-ing. H eat and fire prov oke dilat ion a nd c leav age

Fig . 5 - A typ ic al si te in whi c h an unp r otec t ed m osa ic is s lowl y dis ap pea r ing

in th e h e art of s trat ifica t ion lay e rs, a nd the d es tr uc ti on o f t h e t es s el lat ed l ay e r o r of it sc on s titu e nt m at er ial s.

2. 1.3 . B iolog ical stre ss: P lan ts a n d th e ir r o ots ,m icro -org a nis m s, b urr o win g an ima ls - o f wh ich

ma n is th e m os t dan g er o us s pec ies - all p art i-c ipa te in the d et e rio ra tio n an d d e str uc tio n o f

pa v em e nts a nd a cc e lera te th e de g en er at ive p ro -ces s ; th e te s sell a ted laye r su ffers t he m os t from thi s typ e of dete rior a tion (Fi g s. 5 to 8 ).

9



Fi g. 9 - M os aic tr an sfe rre d to re info rc ed ce m en t. B a dly ins ul ate d ste e l b ar s r us t a nd s low ly s plit th ec emen t and the mosa ic

T o giv e m a n h is du e , o n e n o tes t hat h e ca nb e co m e a w ar e of th e n eg a tive as pe ct s of h isa ct iv itie s an d ca n al so p a rtic ip ate in c o ns e rva -tion an d res tora tion.

2.1.4 . C h em ic al s tre ss : W ater vec tors carr y so lub le s al ts a n d o rgan ic a ci ds. T hr ou gh t he p ro-du cts of th eir c hem ica l or b iolo gic a l tra nsf o r-m a tio n , th e se a ge n ts d ireo tly a ttac k the pa v e-me n t's c ons titue nt e leme nts, par ticul a rly a t th e join t s a n d t h e s t rati f icat ion la ye r s. C hem ica l str e ss c on tri bu te s t o de te rio rati on o f m a te ria ls and the d est ructi o n o f pav eme nts.

2 .2. M os a ics tran sfer ed t o m u seu ms

E xp e rien c e h a s s h ow n tha t the c irc um s ta nc es fav o ura b le to th e co ns er va tio n of a m os aic in i ts o rig in al lo ca tio n ca n ra re ly be a ch ie ve d. C on se -

qu e ntly , th e be s t m e tho d of c on s erv a tio n co n -sis ts o f s ep a ra tin g th e m os ai c f ro m its o rig in a lsu pp o rt a n d t ra ns fe rrin g it o nto a n ew o n e. W ith thi s m e th od , t h e m a te ria ls a nd s tru c tur e of th et e sse llate d la yer, wh ich c ons titut e s th e m ainin ter e st o f a m osa ic, a re c o nse rved .

E ve n wh e n a mo s aic is lu c ky e no ug h to su r-v ive for trea tme nt, it st ill m ust rece ive the a tte n tio n of a su ff ici en tly qua lifie d te c hni c ian .M y fr iend Ro lf W ihr h as s how n us a r e mo valop e ra tio n d one wit h a l a rge r oll e r. T h is di ffic u ltop erat ion w as a com plet e su cces s be caus e R olfis a c a re fu l a nd h ig hl y q u al ifie d te ch n ici an . In

c on tr as t, th is sa m e te ch ni qu e em p lo ye d by a ninsu fficie n tly e xp e rien c ed r est o rer le d to va r iou sca tast rophe s in Sain t-Ro main -en- G al.

Eve n w h en a mo saic is n ot de stro yed by m e-ch an ic al ag en ts , c ar ele s s e xc av a tor s, ad m ini st ra-tive de lays , or inex p erie nce d te c hni c ian s , it isce rt ain ly n o t ye t ou t of d an ge r.

F o r th e p as t t we lv e ye ar s, nu m er ou s Fr en ch mus eum s h a ve sen t us thei r mo saic s, w hich w er t re s tore d i n the p er io d b e tw e en 1 814 an dn o w. A s y o u ca n se e in th e illu s tra ti on s, m o sto f th e m a re in a d is a stro u s s tat e of c on s er-v a tion .

T h e p ri nc ip al re as o n f o r th is s o rry s tat e of a ffa ir s a re d a ng e rou s re m ov a l a nd re s tor a tio np roce dure s, s u ch a s:

c ut tin g of sm a ll s e cti on s w ith o ver ly la rg ein c isio n s; in th e m os ai c of th e D run k en ne ss o fH erc ules , the cut s rep rese nt a bou t 25 0/ o f the total surfa ce a rea ;

cut ti ng w ith o ut r es pe ct f or th e m os a icp a tter n ;

uti liz at io n o f bit um e n, w hi ch im p re gn at es to th e h e ar t o f t he te s se ra e m a te ria ls a nd a lte rs th e m ir rev e rs ib ly;

utili z atio n of anim al g lues whe n tre atm e nt

is lo ng d ef er re d. B iol og ic al pr oc e ss es w e ak en th e glu e; t h e te sse rae are no l o ng e r h e ld t o -g e the r ; th u s t he m o sa ic s ar e l os t.

Ba si ca lly , tr a ns fe r o nt o i na de q ua te ne w s up -p o rts ( wa x , pla s ter o f P a ris, l ime mo rt ar, c em e nt)

b ea rs th e gr e ate s t re s po n sab ility f or d ete ri ora -tion . W ax c an c au se fi re s o n oc c as io n; p las te rh as p oor r esi s tan c e a n d is effe c ted by hu m id ity; th e m ech a nic a l re s ista n ce o f lim e m orta r can notb e ar p ane ls g reat e r th a n 5 0 cm /sid e , s o res to-re rs in c rea s ed th e th ic kn es s an d

, c or re sp on d -in gly , t he w ei gh t. D es pi te th is. th e pa ne ls b ro ke du ring tr an sp or t a nd m a in ten a nc e. Iro n or w oo d br a ce s we re a dde d, b ut o n ly incr e ase d th ew ei gh t w itho u t a vo id ing b re ak a ge a nd c rac k ing .

H ow eve r, th e gra v es t det e rior a tio n is d ue to th e us e of ce m e nt , w h eth e r i t b e m or ta r, re in-forc e d c o nc re te, o r g rout in g.

W h en reinf o rce d co n cret e is u sed on t h e b a cko f a m o sa ic , w h ic h ge n era ll y h a s b e en c ut u pin to sq ua re s o r re ct ang les. th e ce m en t s h rink a ge c a use s th e se s ma ller s e cti o ns to bu c kle . To r e-m e dy t his d ra w bac k , re s tor e rs ha ve l eve led th emo s aic s urf a ce by g rin di ng . A fter th is o per a tion , th e ce nt er te ss e rae i n ea ch s ec tio n a re so m e -tim es r educ ed t o ab out a mil lime tre in thic knes s.Th e c o ncr e te d oes not adh e re w ell to th e te s-se rae, s o th e sl ig hte s t m e cha nica l stre ss c aus e sth in p laq u es - the l as t v es tig e s o f the t es se ra e -to d ro p of f.

W h en e xp os e d t o he at , th e a rm at ur e s w el ls, p ro v ok in g t an g en tia l str es s b etw e en t he c on -c re te a nd th e te sse llate d la y er, w hic h se p ara tesfr o m th e su pp o rt; t he m o sa ic is lo s t. F o r e x -am ple , mo s aic N ° 12 1 o f th e R e cu ei l G e ne ra ld e la G au le, T o m e I L y onn a ise su ffere d fr o mthis pro b lem .

In the p re se nc e of hu m id ity, t he iron o xid iz es; th e inc re as e d vo lu me , du e to ru st (F ig . 9) pr o-vo ke s ta ng e nti al str e ss es w ith a r es ul t s im ila r•

7



\

F ig . 1 0 Mo sa ic fro m th e ea st of Fr an ce tr a n sfe rre d to

a s la b o f c e m e n t u n in s u la t e d f r o m h u m id s o il

u n d e rn e a t h . T h e e fflo r e s c e n c e o f s a lt s , e v id e n t

he re , v ery ra pi dly b r in gs ab ou t t h e de st r uc tio n

o f t he m os aic

Fi g . 1 1 - D e t ai l of F ig. 10

to th e p re c e d in g c a s e .Ut iliz a tio n of ce m en t pr o v ok es a no th er ty p e

o f i r r e v er si b le d e te ri o r a t io n . A s it s e ts , t he

ce m e n t lib e ra te s s ol u b le s a lts th a t m ig rat e to -w a r d t h e s u r fa c e , c o m b in in g a n d c r y s t a lli z in g

in to in s o lu b le c o m p o un d s in the u p p e r p o res o f

the te ss e ra e ; th is g iv es t h e te ss er ae a u ni for m lyg re y a p p e a r a n c e F ig s 1 0 -1 1 ). If h u m id it y o c -

cu rs , s a lt e f flo re sc e n c e s a p p e a r ; c le a n in g

th e m w ith hy d roc h lor ic ac id o nl y i n c re as e s t h e

d a m a g e :

A s lo n g a s n itra te s r e m a in in a m o s a ic , w e h av e a su b s t r a t um w it h a ll t h e c h a ra c t e r is t ic s

fa v ou ra b le to th e d e v e lo p m e n t o f a b io lo g ic a l

d e te rio ra tio n pr oc e s s .

3. In te r v e n t io n

3 .1 . T e ch nic al m ea ns :

U n fo r tu n a t e ly , r e m o v a l i s i n v o lv e d i n m o s t-in te rve nt io n s to s a v e m o sa ic s . S in c e t h e m o s a ics ar e of ten d is co v er ed b y ch a n c e, w e m us t b e

re a d y to m o v e q u ic k ly u n d e r a n y k in d o f a tm o s -

ph e ric c on di tio n s. Fo r th is pu rp o se , w e h av e

th re e tru c ks w hi ch c ar ry te n ts, c om p re ss o rs ,

he a tin g s y s te m s , a n d a ll the h ea v y m a te r ia l n e , c es sa ry fo r d o cu m en ta tio n pr io r t o r em o va l.

O u r v a s t w o rk sh o p p re m is e s in c lu d e : g e ne ra l

w o rk sh o p s (c ar pe n try , m e ch a n ic a l a nd e le c tr i-

c a l); a w o r k s h o p fo r p re p ar in g t he t r a n s fe r; a

lay e r in g w o rk s h o p; a de s ign s tu di o ; a ph ys ic o-c h e m ic a l la b o ra to ry ; a p h o to g ra p h ic la b o ra to ry ; a n d s to ra g e s p a c e f o r d o cu m e n ts , i n fla m m a b le p rod u ct s , bu lk y m a te ria ls . h e ate rs , s to n e, m ar -b le. . . a n d s o o n .

3. 2.1 . P ro tec ti o n

If a m o sa ic is n o t im m e d ia te ly re m o v e d a fte r its d is c o v e ry , c o n s e rv a tio n m e a s u re s m u s t b e ta k e n :

P ro te c ti v e b o rd e r s o f p la s t e r m u s t b e

m a d e a ro u n d th e e d g e s o f t h e p a v e m e n t a n d

th e la c u n a e . C e m e n t m u s t n e v e r b e u s e d . T h e m os a ic s u rf a c e m u s t b e p r o t ec te d

a g ai n s t i n c le m e n t w e a t h e r by c ov e r in g it w it h

a la y e r o f s a n d 5 c m t h ic k , u p o n w h ic h s u b s e -q u e n t la y e rs o f e a rth , 5 c m fo r e a ch d e g re e C b e lo w z e ro , a re a d d e d (F ig s . 1 2 to 1 7 ).

If p o ss ib le , a d ra in sh o u ld b e p la c e d o n a le ve l b e low t ha t o f th e b a se s up p o rt.

3 .2 . 2 . P r e p a r a t ion f o r lif tin g

Th e lif tin g p ro ce ss is p re c e d ed b y th e fo l-

lo w in g p re p a ra tor y m e a s u re s : W he n n e c e s s a r y , th e ar e a i s c le a re d,

c lea n e d , c ov e red , a n d s c af fol d e d.

R u n nin g w a te r, e lec tri cit y a n d h e at ing a re in s ta lle d; g ra p h ic an d p h o to g ra p hi c e q u ip m e n ta re s et u p .

Al l s tr a ti gr ap h ic an d a r c h it ec tu ra l d a ta

ar e co lle c t ed , an d s am p le s ar e g a th er ed f or

a n a lys is .

3 .2 .3 . T h e li ft in g p r o c e s s

A t e m p o ra ry c o h e s io n s y s te m (t o re in fo rc e t h e t e s s e lla te d la y e r) is c h o se n in v ie w o f th e

c h a ra c te ris tic s o f th e tes s e ra e a n d th e su p p o rt, c o n s id e ri n g a s w e ll t h e d e t e r io r a ti o n o f m a t e -

ri a ls a n d t h e s ite c on d itio ns - n o ta b ly hu m id ity .F or th e ad h es iv e, w e ev e r m o re c on si st en tly

re ly o n d u a l co m po n e n t e p o x y s y s te m s, fo rm u -la te d o n th e ba s is o f sy st em a tic te s tin g. (A d e -ta ile d d e s cr ip t io n of th e u s e o f e p o x y r e si n s ,

w ith n am e s a n d a d dr es se s of su pp lie rs , i s g iv en in th e ap p e n d ix ). T o e n s u re th e d im e ns io n a l s ta • b iliity o f th e m os a ic, w e u s e, de p en di ng o n th eci rcu m st an ce s, co tt o n c lot h, fib re gl a s s, or a rig id sy s tem - e ith e r s im pl e o r st ru c tu re d .

W h e n lo c a tion , tim e fa c to rs a n d fi n a n c es p e r-m it u s t o re m o v e a m o s a ic in o n e p iec e, w e u s eei th e r a ro lle r (se e R ol f W ih r s re p o rt ) o r a f la t fra m e w o rk m o u n te d o n ra ils , s u c h a s t h a t e m -

p loy e d a t Sa in t-P a u l- les -D a x.M o s t o f t he t im e, ho w ev e r , w e a re fo rc ed t o

c u t a nd d is m a n tle th e m os a ics b ec au s e o f sit eco n d itio n s , d el a y , d iffic u ltie s in o b ta ini n g c re d it,

7 1



F ig . 1 2 S a in t- P a ul - le s - R o m a n s, m o s a ic p ro t e c te d b y a p o ly e s te r s h e lte r , 2 0 c m o f s a n d , re in fo rc e d c o n cr e te s la b s 80 c m x 6 0 cm a n d 7 c m th ick ,a pla st ic sh ee t a nd a la ye r o f s an d 15 cm d e e p .A n u p p e r l a y e r o f s a n d 2 0 c m th ic k w a s a d de d th e e ig h th y e a r . A s to rm d e s tr o y e d th e p o ly e s te rc ov er ing th e fo u rt h y ea r. R o o ts of bu sh es h av eg row n th ro ug h t he s p a ce s b et we en t h e ce m en ts la bs , t h e pl as tic sh ee t, an d h a ve go n e t h ro ug h th e s a n d to p e n e tra te th e m o s a ic

- Sa in t-P au l-le s- Ro m a n s , roo ts ha ve g row n th rou gh th e t es se lla tu m an d the n uc le us

F ig . 1 4 - S a int -P a u l-l e s -R o m a n s , r e m ov in g the c e m e n ts la b s , w e d is c o v e r a n e t w o rk o f r o o ts a n d t u n n e ls d u g b y f ie ld m ic e

1 111• •••

F ig. 15 - Sa in t-P au l-le s -R o m an s, tu n n e ls d u g by fi e ld m ice in t h e sa n d a n d i n t h e te ss el lat u m i t se lf

in e s tro ye d

• A t. E ;A t

Fi g . 1 6 S a in t- P a u l- le s -R o m a n s , a m o s a ics pi t e of pr ot e c tiv e m e as u r es

•••• r

• 0 - • fit iod ,

74 . , . • • :

Fi g . 1 7 - N a rb o n n e , m o s a ic d e s tr o y e d by roo ts

7 2



• 41ffijm• VV • _r_ • .2

22 _ • ` ••`..•

4 •

D E T A C I-IN E N T . F L E X IB L E S Y S T E M

V V VVV V VV V VV V VV V VV V VV V V V V V V

p 77 t r 4•••••11 - • - • • • -

•g • •

. 0

e a r a it i t e r a is i t

d e t c h m e n t

tu rn in g e rr s

) m o s a ic u p s id e d o w n

Ag it s M il n in o n it n in c lin is a n e t • • • • • • , •••••••• ••••• ••••••••• ••••• •••••••• •• •\ wks••••• • ••• ••••••••••• ••.• • •w••••••.• O •• •••••w

; /

7



D E T A CH M E N T . R IG ID SY S T E M

ed ge pr ot e ct i on r

im eW SIF E 111 11•1 1 1 1 1 /11 /1avi ltinim i 1 rum

R IG ID R E IN FO R C E ME N T S YS TE M

up pe r r ig id s ys t em fr m e w or k dh es i ve i m p re gn t e d f ib r eg l s s ho ne y co m

I // / /

7

th e n e ed to tra n sp ort the m o sa ics hu n d re d s o fm ile s • fro m the sit e to th e w or ksh op , an d t he n e ed to st o re th e m s o m e t im e s t en ye ar s o r m o re .

C u tti n g m u st b e d o n e in r e la tion to t he m o -s a ic pa t te rn a nd wi th a b s o lu te r e s pe c t fo r th e

f igu red de sig n, wh a te ver its siz e; if p oss ibl e ,w e a ls o tr y to m atc h t he dim e n si o ns of th e m o s a ic s ec tio n s w ith th e s iz e o f t h e tem po rar y su p p or t pa n e ls o n h an d : 10 0 x 1 5 0 , 1 2 0 x 1 70 , o r1 5 0 x 30 0 c m .

C u tti n g is a lw a ys ba s e d o n a pr e lim in a ry stu dy an d a 1/1 0 p lan , c a lle d th e r em ova l p lan .

T h e c u tti ng m e th o d d e pe n d s o n th e a d h e r-

e n c e o f th e t e ss e r ae to t h e s u p po r t an d th e h ard ne s s o f th e s up por t.

W he n t h e t es s el la te d l a ye r is no lon ge r a ttac he d to its su pp ort , a sim ple in cis ion be -tw e e n tw o ro w s o f te s se rae is s u ffi ci e nt ,

Wh en the tes se rae a dh ere to the nu c le u s,b ut the la t ter ha s s e pa rat e d fro m t h e rud u s, ar ow o f te s s e ra e m u st b e l if te d o u t a n d t h en u cle us cu t or sa w e d .

W h e n t he te s se r ae an d su p p o rt fo r m a so lid, v er y h a rd ma s s , th e y m us t b e c o mp let e ly s aw ed thr o ug h.

On ce the se ctio ns ha v e b ee n c ut p er p en di-cu lar to the pa v em en t u s in g o n e o f t h es e m e-



N E W S U P P OR T s t L A YE R P R E P A R A T IO N F O R T R A N S F E R

im p r eg n a ti o n

r em o v a l o f o ld su p p o r t

r e s i n m o r t a r —

f ibr eg las s7 7

re in f or ce m e n t s y s t e m

t e m p o r a ry s u p p o r t f o r m o v in g

th od s, we ca n d eta ch the m os aic fro m the lo w er p ar t o f th e s up p o rt. E v e n w h e n th e te ss e lla te d lay e r s ee m s to ha ve se p a rat e d c om p le te ly fro m

the n u cl eu s, it is e x tre m ely da ng er ou s t o a t-

t em p t to d e ta ch it w it h o u t lift in g at le a s t th e

nu cle us at th e s am e t im e. A n um b e r o f t oo ls

ca n b e u se d to d eta ch a m o sa ic: s te e l b lad es of va rio us len gth s o r ( d ep en din g o n the na tur e a nd h a rd ne s s o f t he su p po rt) an ele ctr t o r p n eu ma tic h am me r, or an ele ctr ic o r p ne um at ic s aw fit ted w ith ca rbo ru ndu m or dia mo nd di s cs .

It m u s t b e s ai d th at m o sa ics ar e n o t th e on lykin d o f p av em en ts t ha t w e e nc ou n te r; w e al s ofi n d u n d e c o ra t e d op us su gn in u m te rra zz o

d ec o ra ted w ith c ru s t e or tes se rae , o pu s s e ct ileo f v ari ou s s ort s, e tc. In ea ch ca se, ap pr opr iat etec h ni q u e s m u s t b e d ev elo pe d.

In thi s re ga rd , th e m os aic o f th e G an ag o b ie.p r io r y p re s e n te d a g a m ut of sp ec ial ch a ra c-

te ris tic s a n d c o m p lex d e te r io rat io n pr o ce ss e s .T he tr e at m e n t o f th e s e m o sa ics is th u s a n e x -a mp le o f c on ser vat ion m eth od olo gy. It too k s ev-e ral m o nt h s to b ec om e tho rou gh ly a c q ua in te d w ith the wo rk to ob s er ve phe no me na an d u nd er-st a n d t h ei r c a u s es ; f u rt h er m o n th s pa ss e d in

te st s a n d lab ora to ry e xp eri m e n ts be for e p rep ar -in g a n d p lac ing a t e m p o ra ry su p p o rt sy s te m ,

w hi c h w a s a ls o a n eg at iv e m o ul d . T he re m o v a lits e lf to ok on ly e ig ht h o u rs ; th e p re p a rat io n for re m ova l t o ok s ix m on th s a nd the p lac em en t o f

th e fir s t la y e r o f t he s u pp or t lu st f o r ty h o u rs .3 .3 . Tra n sf er t o a te mp ora ry su p p o rt

W h e n a m o s a ic i s lifte d fr o m t h e g ro un d, i tis ta k e n t o t h e w o rks h o p . T h e re , c o n se rv a tio n

ta s k s m a inl y c o n s is t o f cl e a r ing a w a y t h e l as t

v e s tig es o f th e o ld su p p o r t fr o m th e b ac k o f

th e m os aic a n d e n s u r in g th e c o h es io n o f th e

te ss e ra e o f th e m o s a ic l ay e r b e for e i t is t ra n s -fe rre d o nt o a ne w sup po rt.

W e w ill n o t d w e ll o n t hi s a p p a re n tly s im p le o pe rat ion , w h ic h i n re al ity is e xtr em ely de lic ate

.a n d t e d io u s ; it e ffe ct s t h e e v e n tu a l a dh e re n ce o f t he ne w s up po rt t o th e bac k of t he tes se rae .

W e h av e at te m pt e d to s pe c ify n e w su p p o rt s w it h t h e fol low in g q ua liti e s: pe rfe ct ad he s io n

to the te ss era e, hig h me ch an ica l re si s ta nc e ,

lig h t w e ig h t , c h e m ic al an d p hy sic al n e u tr a lit y ,

and c o m ple te rev ers ib ility .

W e h av e t e st e d a n d u s ed sc or e s o f d iff e re n tty p es o f su pp or t s: p la ste r, s tu c c o , w o o d, lim e

mo rta r, c e m e n t, m e ta l, r e s ins , le tc. W e h av ec o m e t o p re fe r e p ox y re s in m o r ta r r e in fo r c e d

wit h f ibre gla ss fo r th e p rim ar y la ye r. T he ad va n -tag e s of t hi s s o lu tio n ( w h ich m o re ov e r h a s n o d ra w b a c k s ) co m pe n s a te fo r h ig h e r m a te ria l e x -pe ns e s in c om pa ris o n w ith w ate r-b as e d b in de rs.W h e n th is f irs t la ye r h as be en po sit ion ed , th e

m o sa ic s ec tio ns ar e s tab iliz ed ; b e in g in a co n -d it io n of co n s e rv a t io n , th e y ca n b e s to r e d f o r

y e a rs w ith o ut di ffic u lty .

3 .4 . Re st o ra t io n a n d r es tit u tio n

R e s t or a ti o n o f m o s a ic s is o ft e n r e qu ire d

in ord er to de mo ns tra te t he im po rtan ce of sa v-in g th e s e w o rks . R e s tora tio n in vo lve s t h e tra n s -fe r o f th e m o sa ic s e ct io n s in a c o n d iti o n o f c on -s er v a ti o n o n to p e rm an e n t s u p p o rt s, ev e n t ua l

re stit uti o n of lac un a e, an d t rea tm en t o f th e p a-

7



c l o t h g lu ed o n

t e s s e r a e

la c lay e r

fi br eg la s s

b e d d in g m o r ta r

a s se m b ly jo in t s

a er o w e b

Fi g. 18 - L y o n , J e u x d u Ci r qu e tra ns fe rre d t o c e m e nt .F ou rth q u a d ri g a , s t at e a fte r d es tru ct ion b y f ire

F ig . 1 9 - Ly on , J ea ux d u C ir q u e , a ft e r b e ing t r an sf e re dt o a s a n d w ic h a n d r es t o r e d

v e m e n t s u r fa c e a ft e r t h e c o h e s io n s y s t e m h a s be en r em o v e d.

3. 4 .1 . Ne w p e rm a ne n t s up po rt sAm o n g t he v ar iou s pe rm a ne n t s up p ort s tha t

w e ha v e t es te d for m u se um d is pl ay o f m o sa ic s ,s a n d w ic h s tru c tu r e s o ff er th e b es t t e c h ni ca lch a ra c te ris tic s, d e s p ite the ir hi g h c o s t . T h e y a lso c a n b e u s e d fo r o n -s ite d is p la y ; i n th is c a se t h e y p r o t e c t t h e m o s a ic s f r o m h u m id ity a r is in g fr o m t h e s o il. G ive n th e ir t h e rm a l in e rt ia an d w ea k h e at tr a n sm is si on .c o e ff ic ien t. th ey a lso r ed uc e t h e r is k s o f c on d e n sa ti o n .

3 .4 .2 . R e s t itu ti o n Re s t itu ti on o f l a c un a e m e ri ts m uc h di sc us -

s io n b y i t s e lf . I n t h e o ry , n o re s t it u ti o n s h o u ld e ve r be m a d e; h o w e ve r, w e ar e so m e t im e sfo rc e d to fil l c er ta in la cu na e fo r t ec h nic a l, h is -to r ic a l o r a e s th e ti c re a s o n s . In t h is c a s e o n e m u s t b e ca re fu l n o t to b e tray t h e a n c ie n t m o sa ic . T es se ra e ma te ri a ls m u st be r es pe ct ed - i.e . t he

c u t t in g t e c h n iqu e a n d t h e a v e ra g e s ta ti s ti c a ld im e n s io n . T h e e le m e n ts w h ic h c h a ra c te r iz e t h e la y in g te ch ni q u e m u s t b e co ns id er ed : r eg u lar ity or ir re g u la r it y , d im e n s io n s , a n d t h e f o r m o f joi n ts . O u r wo rk sh o p t ec hn ic ia n s a r e no t a u th o-r ize d to fi ll l a c un a e u n t il, th ro ug h p r io r p ra ct ice ,t h e y ac qu ir e a " to uc h " w h ich h a rm on iz es w it hth e o rig in al te ch ni qu e . O n e ca n al w a ys e a sil yd is tin g u is h th e a u th e nt ic f ro m th e r e p la c e d p a r tsb e c a u s e a n e ss e n t ia l p a rt o f o u r w o r k c o n s is t s in e

s t ab li s h ing , d u rin g e a c h o p e r a t ion a l p h a se ,a ll th e g ra p h ic r e c o r d s n e c e s s a r y t o m a k e th is d is tin ct io n : d ra w in g s , p h o to g ra p h s , a n d pe rh ap s m o u ld s . T h e Ly o n C irc u s m o s a ic , w h ic h y o u s e e p ar tia lly d e str o y e d by f ire (F ig . 18 ) an d n ow re st or ed ( Fi g . 19 ), g iv e s e v id e n c e of th e ca re th at w e br in g t o th is op e r a t io n.

m ig h t a d d t h a t th e n e e d fo r re s ti tu ti o n h a s le d u s to d ee p e n o u r k n ow le d g e o f a n c ie n t t e c h -n o lo g y a n d to b a s e a n e w a p p ro a c h to m o s a ic st u d y o n th e st a ti s t ic a l t y p o lo g y o f t e s s e r a e .

7 6



3 .4.3 . F in a l t re a tm e n t o f t h e m o sa ic la ye r

A fte r re stit utio n o f la cu n ae ha s b een m ade ,t he las t s t ep is t rea tm en t an d/o r p olis hin g o f

th e m o s ai c s u rfa c e. Po lish ing is a c o nt ro v e rs ia ls u bj e ct; ho w e v er, we mu st d iffe re n tia te b e tw ee n thr ee cas es:

— T re a tm en t of a h ea lthy su rfac e.

W h en the su rfac e is in go od con dit ion, fre efro m a dv a nc ed ph y si c o- c he m ic al o r b iol o gi c alpro ces se s , s imp le p ol ishi n g w ill su ffice . B y p o-lis h in g , w e m ea n t rea tme nt of t he sur fac e w ith ab ras ive po w de rs (gr a in size 22 0 t o 4 2 0) mi x ed w ith w a te r, u s in g fe lt o r cl o th p a d s m ou nte d o na d isc wh ich rot ate s a t lo w s pee ds . Th e a im ofpo lish ing is to i ncr eas e th e c on stra st of v alu esan d t o h eig hte n t he bril lian ce of the co lou rs.

A t th e s a m e t ime , s ide di f fra cti o n o f l igh t is re du c ed by fla tte nin g t h e m ic ror elie f. In a nti -

q u ity , th e p o lis hi n g o pe rat io n a lw ay s fo llo w e d a fte r th e m os aic had be en pu mic ed wit h s and -s ton e , s an d , o r o the r a b ra s ive s.

— Tre atm en t of a d ete rio rate d s urfa ce .

If th e s urf ace of the tes ser ae is d ete rio rate d,it i s s o m e ti m e s n e ce ss a ry to cle an , re m o ve

sp ots , w a sh , ri n se , re du ce oxi d es , o x id ize or-

g a ni c bo die s, fix s olu ble sa lts , an d r e st ruc ture at a s ca le bet we en a f ew m icro ns to so me

te nt h s o f a m illim ete r.— T rea tm e nt of a v e ry d e te rio ra te d s ur fac e .

D ra s tic m ea s u re s a re r eq u ire d w he n p h ys ico -ch em ica l or bio log ica l pr o ce s se s (o r s om e tim es b o th to g e th e r) h a v e ra d ic a ll y a nd irr e v er s ib ly

a lte re d th e te ss e rae m a te ria l a n d t he ap p e a r-an ce an d le gib ilit y o f a m o s ai c . J ust as a s ur -

g e on am pu tat e s a ga ng ren o us le g , s o th e t e ch -n ici a n m us t re mo ve t he aff lict e d p ar t. T h is m u s tb e d o ne ev e n th o u g h th e a e st h et ic o r h is to rica la s p e c t s u ffe rs , o r w h e n p ro t es t s a ri se fr om

th ose w h o a re mo re c on c er n ed wi th f o rm al p ro -bl em s th an wit h te ch nic al r eali ty. Thi s re mo va lis o fte n d o n e b y g r in d in g ; b y t h is w e m e an a

su rfac e t rea tme nt w ith lar g e g ra in c a rb o ru n du m, c o ru n d um o r d iam o n d g rind in g w h e e ls , t h en w ith m ed ium an d f in a lly f in e g ra in w he els . Th es e ro -ta te mo re r api dly tha n in po lish ing an d a re u se du n d e r w ate r. I t is ne c es s ar y to be gin tre atm en timm ed iat ely af t er g rin di n g in o rde r t o fi x th e

sa lt s a nd bl o ck ult e rio r b iolo gic a l p he n o m e n a. F or th is w e u s e , fo r e xa m ple , a bu ffe re d s o lu -tio n a t 1 / 1 0 ,0 0 0 o f z inc an d m ag ne s iu m f lu o -si lica te. Af t er rin s in g w ith dis tille d w at er, we

gr out the jo ints wi th l ime m orta r.

T he fin a l o pe ra ti on is a m ild p o lis h in g , in s uc h a wa y a s t o a v oi d s h in e a n d r ef le ct ion s .

Cl ear ly, the me tho ds or pro ced ur e s 1 ha ve o u tlin ed ar e n e ith e r ru le s n o r re ci p es , b u t s im p -ly ex a mp les of the app lica tio n o f a m et hod . G iven th e s oc io- e co n om ic an d s o ci o -c u ltu ral circ um -s tan ce s , th es e 'e x am ple s c o ns titu te a pr o vis ion a la n d p a rti a l r e sp o ns e t o ce rta in p rob lem s.

O ne thi n g a lo n e is im po rta n t: the pu rsu it o f re sea rch , of ex p eri me n tat ion , of dia logu e. T ha nks to IC CR OM an d a ll o f yo u, the dia log ue i s o pen .

T he dis cu s sio n w hi c h foll o we d t his lec tur e

w ill b e f o un d o n p a ge 81 .

7 7



AP P EN DIX

Exa mp le o f t r ea t me nt w ith ep ox y re sin s

L if tin g o f a m o s a ic is a p ro c es s w hi c h c on -sis ts o f e n su rin g p e rfe ct c oh e si o n o f t h e te s s el-lat e d la y e r w ith an a dh e s iv e s y st e m a n d th e n s e pa r a tin g t h is la y e r fr o m i ts o ri g in a l s u p p or t. B e fo re ap p ly in g t he te m po rar y c o he s io n s y ste mto t h e m o s ai c, o n e m u s t c a re ful ly e x a m in e th e s u rf a ce of t he te s se rae .

T h e t es s e ra e m a y b e c o v er e d w ith c on c re -t ion s w hic h m us t b e re mo ve d; a s t he ir s t ruc -t u re ma y b e a lte red th e y m u st b e r ein for c ed .T his rei n for cem en t m ay be ac h ie v ed in s ev era lw ay s . If th e m o s a ic is c o m p le te ly d ry it m a y b e im p re gn a te d w ith a s ol u tio n o f e t hy l s il ica te. Th is p ro c es s i s n o t a lw a ys ea sy. On a da m p mo sai c , w e h ave ob tai n ed go od res u lts by usi ng

a 1 % so lu tio n in a n o n -p o la r s ol ve n t co m p o s ed o f: D Y 022 , 1 00 P/w t. * , h a rd e ne r H Y 2 95 4 . 4 5P /w t. O n a d ry m o s ai c w e u s e a s o lu tio n c o m -p os ed of: AY 1 0 3, 10 0 P /w t ., a nd h a rd e n e rHY 99 1, 8 P/ wt. , wh ich ha s a ve ry l ow Ga rdn erin d ex .

Th e c oh e sio n s ys tem is s el e ct e d a cc o rd ing to th e hu mi d ity an d t h e h ar d ne s s o f t h e o rig ina l s up p o rt . It m u s t b e e x tr e m e ly a d h es iv e , e ith e rfle x ibl e o r rig id d ep en d ing on th e s itua tion , a nde as y to re mo ve afte rw a rd . W hen th e m os aic isd ry , a nd th e or igin al s up p o rt is no t to o h a rd , w e us e a fle xib le p ro ce s s. We a ppl y a la y er of

adh es ive an d a she et of c ard bo ard . If the ori gi-o f a d he siv an d a sh e et of c ard bo a rd . If the ori g i-n al su p po rt i s h a rd an d f rag m e n te d , w e u se as h e et o f fib re gl a ss i n st e ad of c a rd b o ar d . I f th e o ri gi n al s u pp o r t is e x tr em el y h a rd w e us e t h efirst m et hod . W e d ivid e t he mos aic int o s tan dar dsi ze se c tion s b y c u tt in g p er e p e nd ic u la rl y to its s u rf a ce , a n d th e n b in d t h e se c ti o ns on t o ri g id p a ne ls.

A ft er so m e ex p e ri m e nt a tio n , w e n o l on g e ru s e o rg a n ic a d he s iv e , or m o s t of t he co m p o si te on e s. On a d ry m o s ai c , w ho s e s up p or t do es n ot p re s e nt d ifficu ltie s , w e u se an ad h e s ive m a d e fro m a d is p e rs io n of c op ol y m e r-v iny l-m ale ic(Rh odo pa s A M 0 41 ) an d a n e mu lsio n o f un pla s-t ifie d p o ly v iny l a c et a te (Rh od opa s A 0 1 0) . Th ep ro p or tion s o f th e m ixt u re are va rie d a c co rdin gto t h e c irc u m s ta n c e s. W e fir s t a p p ly a la y er o fa d he siv e . W he n i it h a s d rie d w e a p pl y a s ec on d lay e r o f a d he siv e o n w hic h w e p lac e a pie ce ofc o tt on c lo th 0 .75 x 1 .50 m . W e u s e a co tto n cl o th o f th e t y pe 24 /18 - 5 6 /7 4 . W e the n ap ply an o th e rla ye rrof ad h es ive to t he clo th a nd le t it d ry . O n th is la st la y e r w e a p p ly a s h e e t o f k ra f t p a p e r(9 0 g /m ). T his co h es ion me tho d h as the adv an -tage of bei ng eas ily rem ove d a fte rwa rds , as we lla s b ein g in ex p en s iv e a n d u nc o m p lic a ted . O n t h eo th e r ha n d , it d oe s n o t ad h e re to a d a m p s u p -po rt, an d it s s t re n gt h is in a de qu a te if t he re -m ov a l e nt a ils gr e at m e c h a ni c al s tr e ss on th e

* P/ W t. = P a rts by w e ig ht .

te s se lla t ed la y er . It a ls o c a n n ot be us e d i f a w a te r-co ole d d iam on d sa w m us t b e e m pl o ye d to r e m o ve tra c e s o f ol d m o r ta r fr om a v e r y h ar d s up p or t.

On a d ry mo sai c, w he n re mo va l en tai ls p ar-tia l de m o liti o n o f th e o ri g in a l s u p p or t, w e u s e a l a ye r of a d h es iv e c om po s ed of A ra ldi te P Y 8 8 0 a n d a p o ly a m id e h ar d en e r H Y 8 0 0 . F o r a ra the r r igid m ixtu re we us e 5 0 % w eig ht o f e po xid e h ard en er, an d f o r a fl e xi b le mi x tu r e w e us e 1 0 0 % h a rd e n er . O n th is la ye r o f a d he s iv e w e ap p ly a la y e r o f c o tt o n c lo th i d e n tic a l to t h at us ed wit h th e v iny l a d he siv e. In c ert a in ca s es we ap ply a s eco nd lay e r o f a d he siv e w ith a la y er o f R ov ing fib reg las s 1 5 0 g /m .

O n a we t m os aic , o r on e e xp ose d t o c on -s ta n t h um id it y, w e ha v e u se d s ev e ra l te c h n i-qu e s: GY 25 0, 1 00 P/ w t. , ha rde ne r HY 8 5 0, 20 P /w t. + H Y 83 0 , 4 0 P /w t. , w ith a la y er o f R ov ing fib reg las s .

G Y 2 5 0 , 1 0 0 P /w t., ha r de n e r H Y 2 9 58 , 15 P /w t ., a nd ot he r fo rm u la e d eri v ed fr o m th e la t te r w it h th e ad d it io n o f h a rd e n e r 94 3 . B u tth es e s y st e m s a r e r igi d a n d n ot ea sily re ver -s ibl e . D es p it e th is, b e g in n in g w ith th e la tte r for m u la , w e h a v e b e en ab le to s p e c ify a c on -tr o lla b le a n d e a s ily r e ve rsi b le a d h es iv e p roc e -d ur e f or a da m p su p p o rt.

Re ce n tly , w e w ere ca lle d u po n to m o ve am os a ic w h ic h h ad be e n c em en te d in 19 3 2 d irec t-ly o n to a 4 0 c m s la b o f ve ry h ar d co nc re te . T h ere m o va l se em ed im p os sib le a nd on ly th e c rea -ti on of a r ig id co h e s io n s y st e m e n a bl e d u s to ca rry it o u t. W e e s ta b lis h ed a s ch e m e f o r c u tt -in g it i nt o p ie c e s, an d f ix e d th e m o s ai c o n to c otto n c lot h w ith the 88 0 a dhe siv e s yste m. W eth en cut the m o sa ic a t ri g ht ang les to its s ur face w ith a w at e r-c o o le d d ia m o n d s aw . W e le t i t dr y ,th e n c ut ou t a n d p re p a r ed wo od sl a t p a n e ls 0 .7 9 X 1 .49 m a nd 20 m m th ick . W e s e ale d t h em o n to t h e c lo th f ix tu r e u si n g a n A ra ldi te m or ta rco m p o se d o f th e f ollo wi n g m a teri a ls :

C o m p on en t A a rt/ w t. A ra ld ite G Y 2 6 0 00

GY 2 6 0 thix o tro pic 0 F lam me x 5 A nti m o n y d iox ide 5Q ua rtz s an d 10 1)

3 5 0

C o m p o ne n t B a r t/ w t.H ard en e r H Y 8 40 0

50

T h e m ixt u re i s c om po s ed of 50 Pa r ts /w t. ofcom po nen t B to 35 0 P a rts /w t. o f co mp on e nt A,i.e . a p ro p o rtio n o f 1 : 7. T o p u t it a no t h er w a y ,4 5 P ar ts /w t. o f h ar d en e r a r e u s ed fo r e v er y 10 0 o f G Y 2 60.

(1) G ra n ul om e tr y: 0 .1/ 0 .5 m ill im et e r.

7 8



A fte r 2 4 h o u r s a t 2 0 ° C . w e we re a b le t o w or k o n th e c o nc ret e w ith p ne um a tic ha mm er s .

In o the r c a se s , af te r th e m o s a ic s ha v e b e e nf ixe d t o t h e clo th , w e e sta bl is h a p la n f o rc u tt in g t h e m u p an d m o vi n g th e m , w h ich is

tra c ed on th e c loth. T h e mo sai c is cu t a t rig ht

a n gl e s to i ts s u rf a ce , a n d if it i s to o h a rd , it is

sa we d . T he s e c tio n s a re d et a ch e d from th e o rigi -na l su p po rt u sin g s tee l bla de s o f va r iou s l e ng ths w ith ha n d le s w h ic h c a n b e h a m m e re d . T h es e bla de s m ay b e u se d m an ual ly o r w ith e lec tric or pn eu m a tic t o ol s . T he sec tion s w hic h h av e b e en re m ov ed are pla ced on te m po rar y su pp orts ma de of c o m p re s s e d w o o d fi br e t re a te d w ith f un g i-

c ide , an d a re the n tr a ns po rted to t he wo rks h o p .

T o e n su re th e c on s e rv a tion of t he de tac h ed m os aics , on e m us t co mp lete ly r em ove an y tr ace so f th e o rig in a l su p p o rt a dh e rin g to t h e b a ck o f

the tes sel late d la yer, a nd rep lac e it wit h a ne w

s upp or t . T he old mo rta r is sa we d a wa y to th e

le ve l o f th e te ss e ra e la ye r in su c ce s si v e c ris s -c ros s r o w s a t rig h t a ng les to t he su rfa c e, w ith a d iam on d s aw . In th is m an ne r it is p os sib le

t o o bt a in sm al l bl o ck s w hic h m a y b e s a fe ly

bro ke n o ff w ith a h an d o r e lec tric ch ise l. D e-

p e n d in g o n th e h ar d n e ss of t he m o rt a r, t hi s

pr o ce du re i s re pe a te d se ve ral tim e s. In c er tain c a se s, the m e c h a nic a l re a c tio n s o f t h e o ld m o r-t a r m a y b e g r ea t er t ha n t h e a dh ere nc e o f th e

t es s er a e t o th e s y s te m o f c o he s io n . It is th e n

n ec es s ar y to co ns o lid a te th e s u pp ort an d t h e

tess era e u sin g an Ar ald ite i m p regn ati o n. De p en d-ing on the cir cum sta nc es, we ch oos e o ne of t hefo llow ing co m b ina tion s :

G Y 2 5 0 , 10 0 P /W t. + HY 8 4 0, 4 5 P /W t. w ith o r w itho u t s ol ve n t;

G Y 2 5 0, 90 P/ W t. + G Y 2 5 0 th ixo tro p ic, 10 P/W t. + H Y 8 30 , 3 0 P /W t. + HY 85 0, 3 0 P /W t.;

G Y 25 0 , 9 0 P /W t. + D Y 0 2 1, 1 0 P /W t. + H Y8 3 0 + H Y 8 5 0 , 60 P /W t.;

A Y 1 0 3 + H Y 99 1, R e s in M + H Y 9 56 , C Y

2 21 + H Y 8 3 7 , e tc.

W e the n c o mp let ely rem ov e th e o rigi nal su p -p or t wi th p ari n g a nd pu mi c ing m a ch ine s, u sin gg rin d st o ne s o f g r ai n 2 4 to 36 .

T h e n ew su p p o rt w ill c on s is t of a l a ye r m e an t t o in s u re t h e c oh e s io n o f t he ba c k s u rf ac e o f

the te s se rae to a r ig id st ru c tu re . T h e firs t st ra-tu m i s fo r m e d b y a l ay e r o f A ra ld it e m o r ta r o f

id e nt ic a l fo rm u la to t h at i nd ica ted on pa g e 7 8 ,to wh ich we ad d A ral d ite pig me nts of t he se r ies DW 0 1 1 t o D N 0 1 8 to g ive i t th e c o lo u r a n d a sp e ct of the or igin al m or tar , an d b y a lay er of R ov ing fib r e g la ss 25 0 g/ m o f th e e po xy- sila ne typ e.

T h e s e ct io ns of mo sa ic a re h ea ted be fore ha n du n d e r in fr a -r e d li gh t s to 3 5° C .; th e Ar a ld it e m o rta r is als o h e a te d t o 3 5° C . in a w a rm wa ter ba th a nd th e n c at a ly z ed at 4 0 ° C . un d e r in fra -re d l ig h ts . T he se c tio n s o f m o s ai c p re p a re d in

th is w ay m u s t ha v e a u ni fo rm t h ic k ne s s f or

ea ch p a v em en t.T his firs t la yer is sol id e no u gh to pe rmi t th e

c on s er vat ion of the mo sa ic s ect ion s - in a m u -s e u m s to re ro o m , fo r in s ta n ce . O n th e o th e r ha n d it is in s uf ficie nt ly s tro ng to a llo w t he res tor a-

tion of the m osa ic. The m o sa ics ma y b e p rep ar-e d fo r re sto ra tio n by s e a lin g t h e s ec tio n s o n to a s u p po r t w hi ch h a s a ll th e n e c es s ar y q u al it ie s. Th e nu m e r o us di ff ic ul ti es en c o u nt e re d i n th e

« per ma nen t" s ett ing of mo saic s h av e le d u s to p refe r tr a ns fer ring mo sa ic s o nt o lig ht a nd las tin g s u p po r ts . F or t h e n e w s u pp o r ts w e g e n e ra lly

u s e p a ne ls co m p o s ed of a l ig ht , ce llu la r h o n e y-com b lay e r s an d wi che d b etw ee n t w o stra tifi e ds he e ts of f ib re g la s s a nd A ra ld ite , ca lled A e ro -we b o r A e ro lam . T h es e s up p or ts a re m a n uf a c-tu re d b y Bo n d e d S tr u ct u re s a c co rd in g t o th e sp ec ific atio ns for th eir par ticu lar ap pli cat ion .

W e u se sup po rts from 3 5 to 55 mm th ick , m e as -u r in g o n t h e a ve r a g e 1 .5 x 3 m , th o u g h i t i s p o ss ible to ob tain an y t h ick ne s s o r d im e ns ion .T h e r e si n s o f t h e o u t er s h e et s a r e fi re p ro o f. Th e se su pp o rt s a r e c ut w it h a n e lec tr ic s a b er

sa w , w hi c h h as sp e cia l b la de s f o r h a rd ma ter ia ls ,the n g lu e d to g e th e r to o bt a in p a ne ls of th e s a m e d ime ns io ns as th e m os a ic be in g res tor e d.

T h e g lui ng of t h e s an dwi ch elem en ts is d one w ith an Ara ldi te b as e a d he siv e u sed at 20 °C .,h av ing the fo llow ing co mp osi tion :

C om po ne n t A - E po xy ar t /wt .G Y 2 6 0 00T hi x otr o pi c a g en ts 10 F lam m e x 20 An tim o ny di o xid e 20 C o lo ur ing ag e nt s 2

DW s erie sS ilic a te s a nd 1 ) 24 8

4 00

C o m p on e n t B - Ha rde n e r a rt/w t.

H Y 840 5 T h ix ot ro p ic a g en tsCo lou ring ag e n ts

DW s eri e sS ilica te san d ( 1) 50

200

T h e c o m p o n en ts a re h e a te d t o 3 0 °C . a n d ar e m ixe d .i n a pro por tion of 2 p a rts A t o 1 par t B ,th e p ot life bei ng app rox im ate ly 4 0 m in u te s . In th is wa y w e a ss e m b le t h e s up p o rt p a n el s in to a s ing le s up p or t e le m e nt m e a s u rin g 3 .50 X 7 .0 0 m . If the mo sa ics are ev en larg er tha n th is, we m a ke s e v e ra l p a n el s w h ic h a re t h en co n n ec te d w ith s pe c ia l jo ini ng e le m e n ts .

W e the n tr ace th e la yo u t o nto th e se pa nel s

w ith a m ar g in o f e rro r o f ap p ro x im ate ly 0 .3 m m .A fte r th is w e c he ck t he se c tio ns of m o s a ic s e tin th eir firs t la ye r o f A r ald ite m o rt a r b ac k e d

1) G ra n ul o me t ry: 0 .1/ 0 .5 m ill im et re .

79



w it h fi b r e g la s s , t h e f ix in g c lo t h h a v in g b e e n re m o v e d , a n d d e te rm in e th e ir fin a l p la c e m e n t .Th e s u p p o rt p a n el s a re t r e a te d to r e m o ve t h e a g en ts u s e d to s e pa ra te th em fro m th ei r m o u ld s . T h e m o s a ic s e c tio ns a re w el l p o s itio n e d , a lig ne d a n d le v e le d , a n d th e n s e a le d o n to t h e A e ro w e b p a n e ls w ith a n A ra ld ite m o rta r i d e n tic a l to t h a t u s e d fo r t he f irs t lay e r .

T h e te m p o ra ry c o h e s io n s y s te m is r e m o v e d ei th e r m e c ha n ica lly w h en t h e p a n el s h a ve s et , or b y he a tin g th e fix in g c lot h w ith h o t a ir a t1 0 0 ° C . fr o m L e is te r ty p e t h e rm o s ta t tu rb in e s .

L a c u n a e a n d s m a ll h o le s a re r e p a ir e d w ith a n tiq u e te s s e ra e w h ic h h a v e b e e n re s to re d a n dc le a n e d , or w ith n e w t e s s e r a e id e n t ica l t o th eo ld o n e s - u s in g a n A r a ldi t e b a s e a d he s ive o fth e fo llo w ing c o m p o sit io n :

C o m p o n e n t A - E p o x y a rt b y W t.

G Y 2 50 e po xi d e 5 0 T hi xo tro pi c a g en t 0 F la m m e x 0 A n tim o n y d io xi d e 0 C o lo u rin g a g e n ts 0

Q u a rt z s a n d (1 ) 00

1 0 0 0

C om p on e nt B - H a rd en er P ar t b y W t.H Y 8 4 0 h a rd e ne r 5 0 B e n ton e 0 0 C o lo u rin g a g e n ts 0 Q u a rt z s an d (1 ) 3 0

1 0 0 0

T h e m ixi n g o f t h e t w o c o m p o n e n t s is p r o -p o rtio n a te ly 5 p ar ts A to p ar t B , an d is ef fe c-t u a t e d a t 2 0 ° C . T h e p o t lif e is a p p r o x im a te ly on e ho u r. P e rm a ne n t h ar de ni ng b y c a ta lys is o f t h e m ix t u r e is o b ta in e d b y h e a ti n g it fo r o n e h o ur u nd er in fra -r ed l igh t at 50 ° C.

N ex t, if n e ce ss ar y, th e mo s a ic m u st un d e rg o p h y s ic a l o r c h e m ic a l t re a t m en t t o co n s o lid a t et h e s t ru c tu r e o f th e m a t e r ia ls w h ic h c o m p o s e t h e t e s se ra e . W e t h e n gr ou t t h e joi n t s w it h a

m o r ta r id e n t ic a l to t h e o r ig in a l. T h e m o s a ic i s p o lis h ed a n d p u m ic ed w it h su p pl e d is c s of 3 2 0 gr ai n . F ina ll y t he m o sa ic is i m p r e g na te d w it h a f lu id s ilic o n e o il, su c h a s S I 2 0 0, to i n -c re as e th e c o lo u r co n tra st , p re ve nt s o ilin g . a n dfa c ilita te e v e n tu a l up k e e p.

A n o th e r e x am p le of th e us e o f re si n s is gi v e nb e lo w . A fl o o r o f lim e c o n c r e t e a n d b ri c k w ith a v e r y in te r e s t ing d e c o ra tio n o f b la c k m a r b le te s s e ra e is di s c ov e r e d b e n e a t h a 5 t h c e n t u r y m o s a ic . T h e lo w e r o n e m u s t b e s a v e d fr o m im m e d ia te d es tru c tio n. Th e co n c re te o f t he fl o o ris f r a g ile a n d th o r o u g h ly s o a k e d . W e c o v e r i tw ith a c l

a y p a s te , a n d th e n a p p ly a s tro n g l a y e r o f r e in fo r c e d p la s te r. W e th e n s e p a r a t e th e lo w e r p a r t o f t h e p a v e m e n t a n d r e p la c e i t w ith

(1 ) G ra n u lo m e tr y : 0 .1 /0 .5 m illim et e r .

a la ye r o f re inf or ce d pla s te r . O n th e p las te r w e se a l a g ri d of 4 0 m m iro n T b ar s. T h e n th e m os a ic , w ra p p e d in th is m a n n e r, i s b o lte d b e -t w ee n fo u r s ta nd a rd I be a m s , ea c h 2 0 0 m m t hi ck . T h e w ho le th in g w ei g h s 3 m et ric to n s, a n d is lifte d b y a cr a n e a n d

tr a n sp o r te d to th e w o rk sh o p . W e l a y it u p s id e d o w n o n t h e f lo o r, re m ov e th e iro n ar m a tu re a nd re in fo rc e d p las te rfr om th e b a ck , a n d le t i t d ry . T h e co n c re te i s to o ro ug h an d fr a g ile to b e de m ol ish e d wi tho u tgr ea t c a re . W e im p re g n a te it w ith a so lu tio n o f.A ra ld ite B Y 15 6 (1 0 0 P ,iw t.) an d H Y 2 .9 9 6 (2 6 P /w t. ) . T h e n w e c u t it w ith a s to n e s a w , a nd im p re g n at e it a g a in . W e re p e a t th is p ro c e d u re te n tim e s . A ll t h a t re m a in s is 2 0 m m o f th e o ld co nc re te , w h ich is p er fe ctl y a tt ac he d . It is c lea n-e d , p u m ic e d , a n d l e v e le d w ith A ra ld ite m o rta r. W e th e n se a l it on to a n A e ro w e b p a n e l. T h e m o -s a ic is tu rn e d o ve r, an d w e fin is h un d re s s ing it. It i s n o w i n t a c t a n d s o lid w it h n o c h a n g e in a pp ea ra nc e.

C on cl us io n

T he p re vi ou s ind ic at ion s ar e e x am p les o f t he m os t fre q u e n tly u s e d p ro c e d u re s, b u t th e re a re ce rt a in ly o th e rs . T h e g e n e ra l a p p ro a ch o f o th e r m e th od s of c on se rv at io n a n d res to ra tio n co u ldb e d ra w n fr o m th is fr a m e o f r e fe re n c e . N e v e r-th e le s s , I w o u ld I, ike t o a d d th a t, th a n k s to th e e xt ra or di na ry p ro pe rt ie s o f th e ep o x y re s in s ,w e h a v e b e e n a b le to d e ve lo p a s e r ie s o f p ro -c e d ur es w h ich h av e pe rm itte d u s to s av e la rg e n u m b e rs o f m o s a ic s p re v io u s ly c o n s id e re d a s g o o d a s lo st . T h e t e s tin g a n d u s e o f e p o x y r e s in s c on s t itu te s a fo rm o f te ch n o lo g y p a rt icu la rl y s u ited to c on s e rv a tio n t ec hn ic ia n s an d re st o re rs .

Na m es an d ad d re ss es of su pp lie rs

B ran d ro d u c t up plie r

Ara ld ite e s in a n d roc h a l Ae ro w e b ar d e n e r p a ne ls , rue B e llini

9 28 06 Pu te aux ,F ra n ce

R ho d op as in y l e m u ls ion s h o n e P o u le n c 25 , q ua i P a ul .D o u m e r9 24 00 Co ur bev oie ,F ra n ce

fir e p ro o fin g a g e n t N o b e l H o e c h st To ur N o be l 9 28 00 P u te a u x ,F ra n ce

fire p roo fin g a ge nt S o ci e te d e s m ine sde la Lu ce tte 4 , r ue de R om e7 50 0 8 Pa ris , F ran ce

pro du ct fo r rom e c om eh ar de n in g s to n e 8 , a ve n u e d u

G e n er a l M ic h e lB iz o t 7 50 1 2 P ar is F r a n c e

F lam m e x

An tim o n y -d io x id e

E th y l s ilic at e

80



DISCU SSION

Th ese not es d o no t att emp t to rep rodu cew ord fo r word t he many c omme nt s and qu es-tio ns. W e have, ho weve r, tried to r ecord th eess enti al po ints, thus sho wing the gen eral direc -t io n of th e discus si on wh ich follow e d the le c-tu res of H err Wih r and M. Bassier .

M. Enn aife r: W e th ank you ver y mu ch for

this in teresting presen tation.Mlle . Ga mso u: woul d lik e to ask Herr Wi hr

w hat i s th e pre fer able adh esiv e fo r mo sai cs,Vinavil?

H err W ihr : We us e a s olu tion o f p olyvin ylc h loride. It s trade n ame is Mowilit h 35/73. I t'sa com pl etely tr an spare nt produ ct which h oldswell a n d is fle xi ble bu t n ot too m uch s o.

Mr. N ovis: I w ould like to cong ratulate HerrWihr for having tried this techniq u e. I've n everh ad the co urag e a nd be sid es I k no w som eo ne

who fa iled in t rying it. D oes the p avemen t stretchwhe n it is ro lled bec a use of p articles slipping bet w een the tessera e ?

H err W ihr: I kno w w hat y ou mean . I'v e as kedSt ef ano Lo c ati the sa me q ue stion a n d he to ld m e there' s no dan g er. I've n ever n o ticed a n yen larg eme nt. I've n ot l ost a sin gle te sse ra. B e-si d es, the s paces b etween the tess e rae are n 'th ar d to c lea n.

Mrs. Al ex ander: H ow do y ou use yo ur rolli n gm eth od o n a room mo saic whe n th e pa vem entgoes rig h t up to the wall? How wo uld you p lace

yo ur dr um in su ch circum st ances ?

Her r Wihr: W e remo ve a ban d of 10 cm allaro und the e dge of th e m osai c, glu ing it on clot hbefore h and, so that the re will b e enough spacefor the whe els of the d rum.

M. E nn aifer : H ave y ou ever cu t a m osa icafte r y ou've ro lled it on the dru m?

H err Wih r: Y es, i n th e se con d ex am ple in my tal k I show e d how w e cut th e mosa ic afterrolling it. By t h at meth od we a voided t he losso f te ssera e.

M. En n aifer: I w ould like to than k M. Bas sierfor his e xtremel y interes t ing rep o rt. Arch a eo-logists a nd art h istorians warmly welcom e thea ssista nc e of sk illed tec hn icians a nd wis h t hat

th er e were m ore o f them. I'd like to a sk wh a tthe se opera tio ns co st.

M. B as sier: B ef ore ans w ering y o ur ques tion,I 'd like to make c lear th at my stu d io, alth o ughwo rkin g ex clus ively for the M ini stere de la Cu l-ture, is a priva te works ho p. It h as total resp on-sib ility for a ll the op e rating c o sts: the buildin g,

ins u rance, in vestme n t, the pu rchase o f tools an d ma terials, r e search , the trai n ing of s ta ff. It ha s to pay du ties and taxes. :t h as to pa y suppli e rs,a nd ab ov e all, it has to p ay a h ig hly qua li fiedteam an d thei r s ocial b e nefits as well. U nderthe se c ond itions , the wor k of savi ng, cons ervin gand re storing mosaics to muse um con ditionscan c o st, in tim e, from. 40 to 60 hours a squaremet r e. Add t o this ou r suppli e s and m aterials a nd the a m ortiza tio n of o ur facilit ies and you rea ch the a mo unt of 4,0 00 to 10 ,000 Fra ncs th esq u are me tr e. I mi gh t add tha t we w ill work on m o saics a s far aw ay as 70 0 k m from o ur stu dio .

M. Ennaife r: Is it d ifficult - in some coun-tries - to get th e nece s sary m a terials?

M. B assier: The ma n ufactur e rs of th e pro-d ucts we use se ll them in all th e count rie s ofth e worl d, but so m e coun tri es pre ve nt the pu r-cha se of th ese pro duct s in diffe ren t wa ys, i norder t o avoid p aying fo r them in hard cu rr ency.

M. Enn a ifer: I w ould like to know whethe r,af te r fiftee n y ears o f using s y nthetic re sin su p-p orts, you have no ticed an y problem of stab ilityor dur ab ility? A nd also, ca n you te ll us w he thery ou find a ny dis ad vantag e s in us in g olde r m e-thods ?

M. Bas si er: I wo u ld reply that we h ave us e da n d tried a ll know n meth od s and th at we a reco n tinuing t o exper im ent wi th new m e thods. It 'sthe proje ct and th e means a vailab le which d e-term ine the meth od to fol low . Cer tain prod uct san d pro ces ses shou ld b e av oide d, •i n the ir tr a-di tional us e, or fo rb idden . T here a re proce ss esc heaper than thos e I've sh own you , and jus t asefficacio us, with certain reserva tions. If youc ould b e absolu te ly sure o f the f ut ure sta te ofa mos a ic, prot e cting it from all d ampne s s and,a ll mech a nical st ress, lim e mortar w ould b e theid eal ma te rial for a suppor t. You ca n also tr a ns-fe r parts o f a mo sa ic, wit h a first co at of e po xyre sin st ren gthen ed with fib reglas s. onto s la bso f reinfo rced con c rete wh ich cou ld have b e en

8



prefabricated independently a year earlier. Thesurface of the slab would have to be adjustedto the individual mosaic placed upon it. Usuallytechnicians don't pay enough attention to thedistortion of reinforced concrete slabs. When webegan to use epoxy resins, we made the samemistake. The mosaic of the Athletes Vainqueursat Vienne curves inward 0.02 m every 7.40 mm;in 1977 we tried to correct it with heat but that'simpossible on a cement slab. To prevent theproblem of contraction and sagging, we no longeruse elements having a surface greater than 15square metres and we balance the pressuresequally on both surfaces of the element.

M. Laffont: Here's a problem: Even if thesurf7cTTIFT mosaic is perfect before beingdetached, should it be polished?

M. Bassier: The decision to pumice or topolish a mosaic is very difficult to make. Firstof all, in antiquity, mosaics were pumiced andpolished. Texts of the time tell us this. We havefound mosaics which still partially preserve theiroriginal polish. The appearance of a mosaic whenit is discovered is most often that of a mo-saic altered by physico-chemical and biologicalagents, particularly when humidity is present.Some people think that this appearance shouldbe preserved for historical reasons. We shouldnot forget that this is not what the mosaic lookslike but what the factors that have changed itfrom its original state have eft it looking like.Examination with a microscope enables us to de-termine the importance and depth of these chan-ges. When they are irreversible, when they hin-der the legibility and the preservation of the do-cument, they must be removed. That's what adentist does with his drill to "restore" a toothwith cavities. We're sometimes forced to do that.It can mean removing one or two mm from thethickness of a tessera. We don't systematicallydo that. It's a drastic operation which we tryto avoid if at all possible. When it is necessary,it must be done in such a way that it will neveragain be necessary to repeat it. Sometimes weonly polish them, using stones wrapped in cloth

and very fine powder, in order to preserve therelief of the mosaic and improve,the contrast

and the brightness of the colours. To pumice amosaic is less dangerous than to leave it toweather unprotected for ten years. At Tivoli I'vefound that some tesserae are only 4 to 5 mmthick, half of their original thickness.

To reply to your question, M. Laffont, if amosaic is perfect before it is laid down, there'sno reason for pumicing it. We've just relaid amosaic of the 1st century B.C. at Perigueux andwe've saved its mortar and natural patina.

Mr. Schwartzbaum: Don't you sometimes alsoremove the layer of resin, polishing the surfacemechanically, or do you have reagents or specialsolvents?

M. Bassier: We use resins which soften at60°C. Although we don't use them to removeepoxy resins from mosaics, there are solventsspecifically for epoxy resins, called Wehasolve.

Sig. Mora: I can't agree :that an electric sawshould be used for cutting.

M. Bassier: You're perfectly right. We usethe saw only when it is absolutely necessary.But we have to face the facts. When you're re-moving a mural, which is rare, it's because,usually, the support is in a very bad condition.Because of that, the painting comes off veryeasily. In the case of mosaics, the mortar isoften in an excellent state. it measures 10 to20 cm in thickness. Removing the mosaic isnecessary and urgent because of factors whichare going to destroy it. The mosaic has to be

loaded on a truck, moved and stored perhapsten to 15 years before receiving any treatment.We have more than 1,000 m of mosaics in ourstudio awaiting restoration. We have to be pre-pared to saw when the circumstances require it.You've just now seen mosaics destroyed by amosaicist who didn't know how to use the sawand we've seen here in Italy mosaics cut outwith a saw.

M. Ennaifer: I thank everyone who has takenpart in this discussion. A great number of pro-blems have been raised, new supports, the costof treatment, pumicing, etc., which centainly

must be brought up again and studied furtherat another meeting.

82



Fig. 1 - A suggestion of the general plan

THE PROBLEM OF LACUNAE IN MOSAICS

by Paul Philippot

Translated from the Frenchby Elizabeth Schwartzbaum

Introduction

The specific characteristics of mosaics - bothwall and pavement mosaics - obviously do notinvolve a different method of approach to theproblem of lacunae than that formulated in ge-neral terms by the modern theory of restoration.The principles already outlined for monuments inthe 1931 Carta del Restauro and in the 1964Venice Charter, as well as the fundamental con-siderations of Cesare Brandi (1) are, in fact,applicable, in the current viewpoint, to all formsof artistic creation. Nevertheless, the means ofapplying this method vary according to the typeof object under consideration, and each domainrequires, in order to meet in an adequate fashionthe general fundamental exigencies, the perfect-ing of special formulae. Although there existtoday dominant methodological principles. westill lack any universal recipes. We will brieflyoutline these fundamental principles at thispoint, before attempting to sketch those aspectsof the problem which are particular to mosaics.

General theory of the treatment of lacunae

In accord with the modern theory •of restora-tion such as is generally accepted today, andsuch as is practiced more and more in fieldswhere restoration, thanks to a longer criticaltradition, has become more rigorous (we referespecially to paintings and archaeological ob-jects), the problem of lacunae must be con-fronted with the basic need to reconcile thehistorical viewpoint, according to which the workof art is essentially a document, with the aes-thetic viewpoint, according to which it is aformal creation. Only by reconciling these twomethods of approach, both of which compel re-

cognition because of the double historic andaesthetic quality of the work of art, can theauthenticity of the work of art be respected.

From the historical point of view, nothing can

justify an intervention on the lacunae. whichconstitute a document, because such an inter-vention would necessarily entail an alteration ofthis document. If the document is to be inter-preted, if a good comprehension of it requiresa conjectural reconstruction, this should alwaysbe done separately, in the form of an explanatorydocumentation, and never on the work of artitself. Similarly, even when the philologist hypo-thetically completes the lacunae in a mutilatedtext, he does it in the editing of the text, ac-cording to precise conventions intended to avoid

all confusion, and never in the original manus-cript.

On the other hand, from the aesthetic pointof view the lacuna, interrupting the continuityof the form, renders the reading of the formmore difficult, and it is henceforth evident thatan intervention on the lacunae should, in cer-tain conditions, allow the re-establishment of abetter reading of the original However, in orderto respect the authenticity of the original, theintervention must be limited to carrying out thesuggestions implicit in those parts preserved(Fig. 1), stopping as soon as hypothesis begins,

83



Fig. 2 - A suggestion of the plan and of the figures

and adopting a process which allows that bycareful examination one can always easily dis-tinguish the intervention - critical interpreta-tion - from the original. To this end, various for-mulae have been experimented with in differentfields with varying degrees of, success (Fig. 2).There evidently does not exist any universalrule which could automatically be applied. Therequirements of the theory can be realized ineach actual case only through a sensitive inter-pretation of the individual work.

Lacunae in mosaics

Generally speaking, the specificity of theproblem posed by mosaics derives on one handfrom the special ties with the architecture ofwhich it is an integral part, and on the otherhand from the technique which characterizes itand which determines its texture and its reac-tion to light. The first condition is analogous tothat which applies to mural paintings; one couldtherefore extend to mosaics the considerationsdeveloped for the treatment of lacunae in muralpaintings (2). The second condition, however,is strictly peculiar to mosaics and will requirea special examination.

The first distinction necessary, which permitsthe application of the same criteria for mosaicsand for mural paintings, is the distinction be-tween the lacunae which cannot be reintegratedby a reconstruction and those for which suchan intervention can be envisaged.

The principle according to which reintegra-tion is justified only when it involves no hypo-thesis, must be completed by the following con-siderations:

1. Even when the reconstruction is not hypo-thetical, as in the case of a solid group or ofa decorative motif which repeats itself exactly,the extent of the lacuna must nevertheless betaken into consideration. In effect, even themost nearly perfect reconstruction cannot passcertain quantitative limits, without asserting it-

self on the general impression and thereby dis-torting the original instead of setting it off.

2. Lacunae are appraised differently whenthe work has remained in situ and when it hasbeen transported to a museum or warehouse.

In situ the work naturally presents itself as anintegral part of the architectural ensemble, andthe lacuna must therefore be appraised in rela-tion to this context. Thus, a lacuna perfectly ac-ceptable in a fragment which presents itself assuch in a museum, can become very offensiveif it gives the effect of a hole in a decorativesystem framing the architecture. Such a situa-tion could then, exceptionally, justify a more ex-tensive reintegration. We refer here to the prin-ciples developed for mural paintings (3). In thecase of wall mosaics special attention must begiven, in this regard, to the luminous quality andto the methods of lighting of the interior space.Old systems of lighting were generally muchweaker than that to which we are accustomed.It would be catastrophic to project our modernrequirements into ancient interiors, all the moresince, as one can easily ascertain, as light growsweaker, the forms become more integrated intothe ambient space, while as the light growsmore intense and more directed, forms andthings become more isolated in their materiality.Thus, colour reproductions of mosaics made,for technical reasons, under a lighting muchmore intense and oriented than the originallighting, completely falsify the effect sought bythe artist. In the same way, modern lighting can-not help making lacunae conspicuous, whereasthe half-light of the ancient lighting systemsintegrated them much more easily into the unityof the interior atmosphere, where the image inmosaics reveals itself slowly, like a progressiveapparition. One should therefore attempt to makethe best of the lighting before deciding upon anintervention on the mosaic itself.

Reintegratable lacunae

When, within acceptable limits, it is decidedto reintegrate the lacuna, the problem arises ofreconciling this reintegration - justified only asa setting off of the subsisting original by a re-establishment of continuity - with the require-ment of historical criticism which holds that theinterpretation can be distinguished as such undercareful examination, in order to avoid all riskof falsification.

An immediate result of the preceding con-siderations is the fact that today one can nolonger accept a reconstruction executed withold tesserae or even with modern tesserae which'attempt to be indistinguishable from the original.Indeed, this type of retouching, of which themosaics of Rome offer numerous examples, ap-pears today, less than a century later, as a"romantic" falsification.

84



E ve n w he n i t is a q u e s tio n o f a u ni fied su r-fa ce - s u ch a s w h ite , b lu e, g re e n o r g o ld g ro u n ds -o ne sh o u ld r e m e m b e r th a t t h e p la c in g o f th e

tes s er a e i s d e te rm in ed by t he cre ati o n o f e ffec tsof lig h t r e fle ctio n, a n d th a t m o d er n s e tti n g c an ne ver re cap tur e th e in fin itel y su btl e p lay of the

o rigi n al s et ting bu t a lw a y s s tan ds o ut off e ns ive -ly b e c au s e o f i ts m ec h a ni ca l, h a rd qu a lity .

T h e a tte m p t to r e co n c ile r e co n s tr uc tio n w ithv is ib ili t y o f re tou ch ing by sk e tc h in g th e f o rm s

w ith m as s e s o f so ft c o lo u rs , ap p lie d in p a in t on a sm oo th s ur fac e a t th e le ve l of the te s se rae ,

a s in the na ve o f S an ta M ar ia M ag g io re, is h a rd -ly sa tisf yin g, f or i t cre ate s a re al o ptic al d iso rde rw hic h e x te n d s to th e o rigin al w ith ou t, h o w e ve r ,re in teg rat in g t he lac u n a .

G iv e n the imp ort a nc e i n a m o s ai c of the pl a yof t he su rfac e t e xt u re o b ta in e d b y m e a ns of the tess era e ( cut , fo rm, ma ter ial, an gle of set ting ),it s e e m s t ha t re se a rc h s h o u ld b e o ri e nt e d t o-wa rd a s o lu t ion an a lo g o u s to t h at o f trat teg g ioin p ai n tin gs , th a t is , to wa rds a u se of tes se rae a n al o go u s t o th e o rig in a l b u t n ev e rt h el e ss dif -fe ren t, c a pa ble of ass uri n g a s u ffic ien t in teg ra-ti o n w h ile a t t h e s am e t im e r e m a in in g s lig htl y

d isti n gu ish ab le b y t h ei r m a te r ial . A dis tinc tio n

in th e m at e ria l ra th e r t ha n i n t h e sy s te m o fse tting s e em s r eq uir e d , si n ce it is p r ec ise ly

th e sta cca to res ult ing fro m the se ttin g o f th e

t es s er a e t ha t is th e d e te r m in in g f a ct o r i n th e

r hy t hm o f a mo sa ic, t he co nti n u it y o f w hi c h

m u s t b e re -e s ta b lis he d b y t h e re in teg rat io n o f

the la cun ae . O n ce th e d istin ctio n h as be e n a s-s u re d b y t h e m a ter ial i tse lf lw h ich co u ld , fo r

e xam p le, g iv e a so ften ed re flec tio n o f lig ht) ,

th e re i s n ot hi n g to o p po s e a v e ry h ig h ly d e ve lo p -e d r ein te g ra ti on , a s lo n g a s i t i s a q u e st io n o f

a sm al l la c un a, t he re inte gr a tio n o f w h ic h in -

v olv es no hy p ot h es is. T o our kn ow led g e, how -e v er , no ex pe r im e nt s ha ve ye t be en att e m p te d in th is d ire c ti o n.

N on re inte gra tab le l a cu n ae

W he n , b ec a us e o f it s d im e nsi o ns or its lo-

ca tion , a lac un a is no t re int e gr a ta b le , th e re re-m ain s th e p ro b le m o f p r es ent atio n. sin c e o ne

m us t a lw a y s r ed u ce a s m u ch a s po ss ible th e

d is tu r ba n c e c a us e d b y t h e la c u na in o rd e r to

re in fo rc e t h e u ni fie d ef fe c t of t he wh o le . O n c e a g a in , ins p ira tio n is dr a w n f r om th e g en e ra l

co ns ide rati o ns on the tr e at m e n t o f la c un ae de -v e lop e d b y C e s ar e B ra n d i b a se d o n th e P s y ch o -lo gy of F or m a c co rdi n g to w hic h o u r p erc ep tion s a lw a ys tak e t h e s ha pe of r el a tio n s b e tw e e n a f ig u r e a nd the gr ou n d a ga ins t w h ic h it sta nd s

o u t ( 4 ). N on -in teg rate d la cu n ae sh o ul d th e re for e b e t rea ted so tha t th ey do no t "c ut a fig ure " o nt he im a g e a s a w h o le , w h ic h t h en re c e d es t o

th e s ta tu s o f a b ac k g ro u nd , b u t o n t h e c on tr a ry 's o th at they co nst itut e th e g rou nd aga ins t w hic hth e frag me nts of the im age st and ou t re un ited .In p ra c ti ce , o n e c o ul d d ra w in s pi ra ti o n in t h is

re g ar d d ire c tly fro m the ex per im e nt s c arr ied

o u t in t he do m a in of m u ral p a in ting s ( 5 ).

W he ther it i s a q ue stio n o f p a ve m e n t m os a ics o r w a ll m o s aic s, the mo st s at isfa c to ry s olu tio n d e fin ite ly a pp ea rs t o c on sis t in tre at ing the la cu na like a laye r o f a rric c io u nc ov e re d b y th e

f alli ng of t he in ton a co a n d t he te s se rae . T h eslig ht re c es s i n re la t ion to th e p lan e o f t h etes se r ae , a s w e ll a s t he tex tur e a n d c ol o ur of

th e m a te ri al , ju d ici o us ly ch o s e n in i m itat io n o fo r in s pi re d by th e o ri gi n al ar ri cc io a llo w s the p e rc e p ti on of all the la c u n ae as pa rts of the sam e g rou nd pla ne in fr o nt o f w h ic h the m o sa ic im ag e s tan d s o u t cl e ar ly , w ith o u t ris k o f in ter -fe re nc e o r of co n fu s io n (F igs . 3 , 4) . It is t h er e -fo re n e c e ss a r y o n th e o n e h a n d to ta k e c ar e

to t re a t al l of t he n on - re in t eg r a te d l ac u n a e in

t he sa me wa y, in o rd e r t o in su re t he un ity of

the gr o un d p la n e, wh ich be co m e s th e m u r al

pla ne of r ef e re n ce ; a n d on the o th e r ha nd to pr e ve n t a t a n y c os t th e ne ce s sa ry r e in fo rc e m e nt of t he ed g e s o f th e la c u n ae fr om s ta n d in g o u ta s a n in de p e n de n t fig u re b e tw ee n t h e te ss e ra e a nd th e g ro u n d. In r e ga rd to t h e la tte r, e s p ec ia llya s c o n ce rns w al l m os a ic s , it sh o u ld p re se n t a co lo u r a n d te x tu re w h ic h a llo w it to b e a s w e ll

F ig . 3 - M is s ing te ss er a e le av e th e o ri gin a l s e ttin g b e d

exp o sed

85



ha s n ot b ee n fi lled an d le ave se xpo s ed

Fig . 6 - T he lac una is fille d w ith a g los sy sur face

F ig . 7 - Th e la c u n a i s fi lle d w ith a r ou g h s ur fac e

F ig. 4 - T h e la c un a i s fi ll ed wi th a sl ig ht ly d ep r es s ed

su rfac e r e se mb ling a s etti ng b ed

in te g r a te d a s p o s si b le , s li gh t ly re c e s se d , i nt o

th e o p tica l w e b cr e a te d b y th e t e ss e ra e i n th e p ro pe r b igh tin g . T hi s i s a m att e r, as on e can

ima gi ne , of a ve ry d el ica te ch oic e, wh ich re -

q u ires a g re at ae s th et ic s en s it iv ity o n t h e p a r to f the re s to re r , a n d w h ic h is m ad e e ve n m o red iffic ul t b y th e m o d ific a tion s o f t o n e th at o c c u ra s th e pr e p a ra tio n d ri e s. A n e r ro r o f t e xt u re

o r o f c o lo u r - a s i n t h e c a s e o f t h e b r ic k -r e d

la c u n a e o f t he ro t u n da o f S t. G eo r g e i n S a lo -

n ica - i n e v ita b ly re s u lts in d isp lay ing th e l a cu na a s a fi g u r e in s t ea d o f m a k in g i t re c e d e to t he

s ta tus o f ba ck g ro u n d .Tw o f or m u lae o fte n m et ar e , i n o u r o p in io n,

to b e a v o id e d b e c au s e th e y d o n o t a llow in an y ca se th e s pa tial so luti on jus t d es c rib ed . T he se ar e :

1 . T h e rev e a ling of th e w a ll in la c u na e . s ho w-in g st o n e o r b ri c k in its b ru ta l a n d d ire c t m a te -r ial ity, in vio len t c on tra s t w ith th e f o rm al re a lit y o f t h e o p tic w e b c re a te d b y the te s se ra e , w ith the re su lt t h at th e w al l, in st ea d o f s erv ing a s

g ro u n d , cu ts a f ig u re , to th e d et rim e n t o f th e m o sa ic ima ge . T his ca n b e s ee n in c e rta in pa rtso f K a ri y e D ja m i w h e r e r es t or a tio n h a s le ft t he

b ric k w o rk ap pa ren t ( F ig . 5 ) .

2 . T h e t rea tm e n t of la c un ae w ith a s m o ot h p rep ar a tio n, wh ich re fle c ts th e li g ht to o h ars hly in r ela tio n to th e d iffu sio n c au se d b y t h e m o sa ict e s se r a e , th u s c a u s in g a c o nt r as t d e tr im e n ta l

to inte gr ati on . T his so lut ion w as als o trie d a t

K a riy e D ja m i, w h e re it i s a ll t h e le s s s a tis fy in g be ca u se it i s a dj a ce nt , in c oh er e n tly, to the pr e -ce d in g s o lu tio n ( F ig . 6) . It s h o ul d a ls o be po int e d

o u t th a t th e a d d it io n of a p a in t e d c o lo u r g e -n e ra lly ru n s th e r is k o f a gg ra v at in g th e s itua tio n w ith a gl a ze d eff e c t . O ne m us t a lwa ys tr y t o

8 6



ob tain the d esired o ptical v a lues in the colo u rand t extu re o f the pre para tion itse lf, by se lect-ing th e prope r in ert su bs tance .

In th e c ase o f p aveme n t mosa ics , treat m entof non -reint eg rated lac unae is o bviou sly simpl er

bec aus e th e co nst itutio n o f the pla ne o f th elacu na as the grou nd plane of the im ag e is l ess subt le and le s s delica te (Fig. 7 ). On th e otherha nd, one c ou ld cov er t he arricc io with a layerof grad ed grave l a dapte d to the dim ensio ns ofthe te ss erae, in order to reinfo rc e the ide a ofearth (Fig . 8). Thi s sup pos es, h owe ver, that thev isitors w ill not w alk on th e mosa ic.

Th e d iscus sion whi ch follow ed this lect urewill be found o n page 8 8.

Notes

1 C esare B randi, Teor ia del Rest auro, Rom e, Ed izion i diS toria e L et teratura , 1 963.

2 Pao lo an d Lau ra M ora a nd P aul P hilip pot, La C on-serva tion d es pe intur es mu rales , Bologn a , Compos ito ri,1977, C h apter Xi a nd bibliog raphy.

3 Ibi d.4 Cesare B randi, II tra ttamen to delle lac un e e la G es talt-

psy cholo gie XX I nter nationa l Co ngres s of the His tory of Art Ac ts Prob lem s of th e 1 9th and 20 th Cent uri es.IV Stud ies i n We stern Art, New York, 1961 .

5 See note 2 ab ove.

8



DISCUSSION

These notes do not attempt to reproduceword for word the many comments and questionswhich followed M. Philippot's lecture. We have,however, tried to record the essential points,thus showing the general direction of the dis-cussion.

Siq. Mora: The method of approach to theproblem of lacunae in mosaics doesn't • differfrom that expressed in general terms in thetheory of restoration. These principles are ap-plicable to all artistic disciplines.

But even if we have methodological princi-ples, we don't have universal formulae. We mustapply theory to practice and. in the specificcase of wall or pavement mosaics, there areproblems which differ from those of other artforms.

Speaking generally, the theory of restorationhas aquired a certain rigidity regarding theproblem of lacunae in paintings and archaeo-logical objects. We must face the problem ofreconciling the •historical point of view, forwhich the work is a document, and the aestheticpoint of view which sees it as an art object.Only by reconciling these two diverse ways ofapproaching the work can we be sure that itsauthenticity will be respected.

There are no new formulae to follow, onlygeneral outlines.

I would like to ask Mr. Novis how he handleslacunae.

Mr. Novis: In the case of mosaic pavements,I normally fill little gaps with tesserae takenfrom the outer borders. In this way, the tesseraearound these internal lacunae are reinforced. Thistechnique avoids a moth-eaten appearance andalso prevents the loss of, other elements. Thissystem has already been accepted by othersand I hope that it will be here too.

Sig. Mora: That seems very logical to me,rather than filling these spaces with other ma-terials. But it would be better to do it withtesserae whose original placement is unknown.

Mrs. Alexander: Some future discussion onlacunae in mosaics in situ would be a great help.In Tunisia, the situation is such that there arehundreds of mosaics which cannot be removed.I hope that you will give this problem yourattention.

Mr. Novis: I've often judged it necessary andconvenient to set three new rows of tesseraalong the destroyed edges of mosaics in situor around lacunae, in order to prevent furtherdeterioration. It's a way of helping, can be donefri very little time and costs little but it shouldbe done only on a mosaic in good general con-dition.

Sig. Robotti: In regard to the preservationof mosaics at their sites, and the restoration ofmissing parts, I think it's essential that we referto the basic recommendations contained in the.

International Charter of Restoration, that is, theCharter of Venice 1964, and in the Charter ofRestoration 1972. In regard to the first problem,we should resort to transferring a mosaic to amuseum only in case of absolute necessity. Thisbrings up several preservation problems, be-sides those of legibility and of presentation. In

treating lacunae, we should exclude the restora-tion of images because that would mean a re-turn to the practices of the 19th century. Thedifficult and really urgent cases however, shouldbe studied by a committee of experts to decideon the best way to avoid the errors of the past.

Mr. Schwartzbaum: Perhaps you could applyto certain problems encountered in Tunisia thesame method Mr. Novis uses in England on amosaic pavement preserved in situ. A generalconsolidation was done and the mosaic was re-covered with earth after documentation.

M. Bassier: It's always desirable to preservemosaics in their archaeological context when-ever possible. Unfortunately, we often have onlya few hours before they're destroyed by bull-dozers. Besides, they must be protected againstthe weather and against dampness coming fromthe soil. That's why moving mosaics is unfor-tunately o en the .only solution.

M. Enn ifer: We encounter similar conditionsin Tunisia.

M. Bas ier: The problem is simple. Eithermosaics are exposed to the destructive agentsdescribed by Dottoressa Veloccia in her paper,

and the mosaics keep changing under their ef-fects until they are totally destroyed, or themosaics are protected from such damage andtheir preservation in a museum or in situ canbe assured.

Some conservation methods in situ aretoo often an absence of method. They tend tohide the causes of change without remedyingthem. In less than a century,if we don't takecare, the mosaics exposed to the weather with-out any protection will have disappeared. Con-servation in situ should require two conserva-tion operations first: removal and transfer to anew and appropriate support; protection againstthe weather and against biological damage.

M. Ennaifer: From the cultural point of view,moving a mosaic from its site is regrettable.

M. Bassier: Either you remove the mosaicsto preserve them, or they're lost.

M. Ennaifer: I would like to be optimisticand I hope that some future method will resolvethis problem.

Sig. Robotti: From the different points ofview expressed during this discussion, it's clearthat a new approach to problems of mosaicpreservation is needed. This approach should bebased, above all, on control of the environmentand on the definition of the most efficient means'of treating mosaics, so as to guarantee thesurvival of our civilization.

88



THE RESTORATION AND CONSERVATION OF MOSAICS IN TUNISIA

The Importance of mosaic collections

Tunisia possesses the most remarkable mo-saic collection in the world today. Its wealth inthis field greatly surpasses its means of con-servation. The National Institute of Archaeologyand Arts (I.N.A.A.) makes every effort to developthe study, the restoration and the appreciationof these pictorial documents. For this purpose,the Institute has undertaken the long and dif-ficult task of compiling the Corpus of Mosaicsin Tunisia. A first volume in three parts, devotedto the region of Utica, has already been publish-ed. The mosaics which have been preserved andstudied only represent a small percentage ofthose excavated during the course of the lastcentury, and of those continuing to be dis-covered. The spread of urban development, mie-chanized agriculture and industrial plants is pro-viding countless discoveries. Thus, the Institutemust intervene without delay and throughout thecountry. The scarcity of qualified personnel, thelack of appropriate equipment. the climatic con-ditions (the humidity level being generally high),erosion and the fragility of the mosaic pave-

ments are all factors which contribute to theloss of these often unrecorded art works.

Method of conservation

Tunisia continues to use the method of layingthe pavements on a support of reinforced con-crete or plaster. It is true that this system pre-sents certain problems. But the laying of thepavements, being done in workshops and theirdestination being usually a museum, thereforesecure from bad weather conditions, the pro-blems engendered by reinforced concrete standsare somewhat reduced. We are, however. in

favour of the use of synthetic resins. Our recentattempts at creating a stratified "sandwich"

by Mongi Ennaifer

Translated from the Frenchby Patricia Bonicatti

reinforced by layers of fibreglass have beenrather successful. Our main problem in usingthis effective method is the difficulty of import-ing fibreglass.

Restoration

In the field of restoration we are tryingequally hard to improve our techniques, whichare still at a handicraft level. Our concern is toprotect the homogeneity of the work, intervening

cautiously, both with mosaics remaining in situand those preserved in museums. At Thuburbo-Majus, where the work on the Corpus of theMosaics of Tunisia is currently going on, wetried to fill in the important lacunae by usinga lime mortar of cement and sand, inlayed withpolychrome pebbles. This method has been usedelsewhere, notably in Algeria, but is not wellproved yet. In the field of museum exhibits, wehave recently eliminated a good number of theold "reconstitutions". Their colours were farfrom adequate, and the reconstitutions of thechronology and of the scenes were sometimesinexact and even fantasied. One example is thecase of a doorstep of a house at EI-Jem with apattern of five rings decorated by a fish, crown-ed by the digit 5 . As the rings were mistakenfor a part of the frame, the restorer ,thought itwas logical to continue them. He did not estab-lish the connection between the digit "5" andthe sodality of the Pentasii. This poor recons-titution is not unfortunately an isolated case.Thus, one should only reconstitute the motifsof which one is absolutely sure and should com-plete them as much as possibile in the sametones as the mosaic. When important lacunaeare involved it is sometimes useful to unobtru-

sively suggest the composition lines to facilitatecomprehension by the public.

90



T HE AC TI VIT IES O F T H E DE PA RT ME NT O F A N T IQU IT IES O F TH E H A SH EM IT E K IN GD O M O F J O R D AN

O n b e h a lf o f th e D ep ar tm e nt of An tiq u it ie s o f th e H as h e m ite K in g d o m of J o r da n a n d th e

Di rec tor of A n tiq u iti e s, D r. A d na n H a d id i, I w is h to ex p res s m y g ra titu d e f o r be in g in v ited to pa r-ticip ate in th is v er y im po rta nt inte rn a tio na l c o n-fe re n c e . I es p e c ia lly w o u ld l ik e to th a n k th e

D ire c tor of t h e IC C R O M C e n tr e , a s w e ll a s i ts

m em be rs. As y o u k no w , J9 rd a n is l o ca te d in th e g e o -

g ra p h ic c en tre of th e A ra b w or ld. It c on ta ins

s o m e o f t h e m o s t a n c ie n t a rc h a e ol o gi c a l s ite s in the wo rld - f rom t h e be g in n in g o f c ivili za tion ,s u c h as th e n e o lit h ic ci t y o f J er ich o, t o t h e

fl ow eri n g of an c ie nt c ul tur es in suc h s ite s a sN a b a te a n P e tra , R o m a n J e ras h , B yz an tin e M a -d a b a a n d Is lam ic Je ru s al e m , w ith i ts D o m e o fth e R o c k , as w e ll a s t he Is lam ic ca s tle s in t h e J ord an ian de ser t.

O u r c on fe re n c e t od ay de al s a b o v e a ll w it h

th e p re se rva tion o f m o sa ic a rt . It g iv e s m e gr e at p le as u re to b e a b le to r e tu rn to IC C R O M a s a rep res en tat ive of the D e pa rtm en t o f A nti q ui ties o f J o rd an , fo r I fir s t s tu d ie d m os ai c p r es e rv a-

tio n in I taly in Ro me an d R av en n a in 1 96 4. S in c ere turn ing to Am m a n , I h av e b e en e n ga ge d in th e re s tor a tio n o f a ll m os a ic s d isc o v e re d i n J o rd a n . I wo uld li k e t o s ay a wo rd ab o u t th e a ct iv it ies .

o f t h e Jo r da ni a n go ve r nm e n t in t he fie ld of

m osa ics .T h e re ar e th ree o u ts ta n d in g e x am p le s o f m o -

sa ic a rt in J or d an . T h e fir s t i s th e i n co m p ar a b ly b ea uti ful a nd im po rtan t M ad a b a m a p of P a le st ine J ord an , S ina i an d p ar ts o f. E gy pt. Th e s ec o nd is th e M u k h a y a t m o s ai c p a v e m e n t; a n d t he th ird is th e T re e o f L ife an d B a th H a ll p a v e m e n t s

a t H ish am 's Om m a yy ad Pa lac e in J e ric ho . A ll of the ab ov e m os aic s h av e b ee n k ept in the ir o rig i-na l lo c a t io n s b e c a us e th e l a n d h a s b e e n p u r-

c ha se d b y th e J or d an ian go ve rnm en t.T hr e e m o sa ics , t h e M a d a b a m a p, t h e M u -

kh a y a t a nd M o u n t N eb o p av em en ts a re un de rthe pr o te c tio n o f C hr isti a n reli g io u s g ro up s . T he go ver nm ent ha s b ee n m os t a ctiv e i n p urc has ing

by Mo ha m m ed G h ou j

O rig in a l te x t in E n g lis h

pr o p e rt ie s co n ta ini n g m o sa ics in o rd er to p re -se rve th e m fo r po st e rit y. F or ex am ple , fo ur pr i-va te h ou s e s c o nt a in in g m o s a ic s w e re p ur c h as e d in M ad aba a lon e.

F un d s f or th e d e ve lo p m e n t of t he c o ns e rv a-tion pr ogr am me an d t he tra inin g o f yo un g m os aic e x pe rts m u st b e r ai s ed in o rd er t o s ol v e J or d a n 'sim m e d ia te p ro bl e m s . O n e o f ou r m os t p res s in g n e ed s is f o r s ch ol a rs h ip s to a llo w p ro m is in g

can di dat es in mo sa ic stu die s t o p ur sue th eir

res e ar c h . Th es e s c h o la rsh ips wo uld e n su re o u rco un try sp e c iali s ts of i ts ow n in t h is im p o rta n tar c ha eo log ica l fie ld. In a dd itio n y ou ng Jo rda nia n

s tu d en ts wo uld ha ve the op po rtu n ity to lea rn the la te st tec h n iq u e s o f m o s ai c c o ns e rv at io n .

T h e fa m ilia r m e th o d o f g lu in g m o s a ic s a n d u si n g ce m e n t a nd st ee l fra m e s for tra n sp or t ing th em l e av es m u ch to be de sir ed . W e i n J o rd an a re v er y m uc h i n n eed o f as sis tan ce an d info r-m a tio n i n th es e m at ter s . T he An tiq uiti es De par t-m e n t h as re c o g n iz e d th e fa c t th a t o u r c o un try is ve ry r ic h in m os a ic s .

J or d an h as the ra re ho no ur of hav in g tw o

m us eu ms fo r m os aic s. Th e l a rg er of the tw o

co lle c tio ns is in the R o m a n t he at re in A m m a n ,w h ic h h as be en de sig n ed to di s pla y a nd pr e se rve

in d ivid ua l m os a ic s d isc ov e re d th r o ug ho u t t he ki n gd o m . T h e s ec on d m us e um lo ca ted in Je ras h c o n ta in s R om an a n d B y z an tin e m os a ic s e xc lu -si v el y . A n e w w in g o f th e m u s e um a t M a d a b a wil l so on co nta in mo sa ics wh ich a re f req ue ntl y u n c o ve re d d u rin g b u ild in g a n d roa d c o n s tru c tio n.

I h av e t r ie d t o p r es en t b r ie fly t o y ou s o m e

o f th e re c en t a c tiv itie s i n w hic h t h e De pa rtm en t o f A n tiq uit ies ha s b ee n e n ga ge d a nd to d e s cr ib e a fe w o f th e w a y s in w h ic h I C C R O M m ig h t a s-s ist u s in fu r th e ri n g t he d e v e lo p m e n t o f th is

im p o rt a nt b ra nc h o f c o n s er v at io n . W e w o u ld b e g ra te fu l for an y f u rth er he lp tha t y o u mi g h t be a b le to pro vid e.

A s w e s a y in A r a b ic , s h r u kr a n j a ze e la n -

th a n k y ou ve ry m u c h .

9 1



F ig . 2 - Glu in g cloth to the face o f the mo s aic in or de rto hold tesse rae i n plac e du ring t he pr ocess oflifti ng

THE TRE ATM ENT OF MOS AIC PAV EME NTS IN S YR IA SIN CE 1939

by Raif Haf ez

Tr a nslated f rom the Frenchby Pa tricia Bo nicat ti

S yria is o ne of th e world s riches t reposi-to rie s of a nc ient m os aics. I w ould like brie flyto t ell you a bout the metho d of. det a chmen t and r estora tio n of fl oo r mosa ic s used in Syria since 19 39.

Li fting

1. C lea r awa y t he de bri s, rei nfo rce th e l a-cu n ae and w eak ed ge s with m ortar.

2. C lean th e mosaic pavem e nt with w ater,u sing bru s hes, sp at ulas an d pointed t ools. So m e-tim es a be d of lime and ea r th accum ulates o nthe s urface o f the pa v ement. In this ca se, thesurfa ce must be clean ed with h yd rochlo ric acidd iluted w ith wat er . The c le aning m ust be a de-qu ate. It ca n be do ne in the mos t co nven ien t

w ay.3. Phot ogra ph th e m osai c pa veme nt, its sit e,and the detai ls of the pan els.

4. D ra w a g en eral s ite plan a s well as ad eta iled plan of t he m osa ic p anel s. Th en cutthe m osaic p avemen t into pan e ls (Fig. 1 ).

F ig. 1 - Mo saic p ave ment cut into p ane ls to a llow itsremoval

5. T he size o f the pa n els sho u ld be de c ideda ccording to nece ssity but should n ot exce ed220 x 180 cm .

6. Wa sh th e b indin g c loth, cu t it in to t hes izes ne e ded, an d then ro ll it up.

7. Spre ad white synthetic glue on the surfa c eof th e p anels (ap prox ima tely 1 /2 m , de pendingo n the wi dth o f th e clot h. Lay th e cloth dow non the g lued su r face an d slap it w ith bru s hesto inc rease ad hesio n (F ig. 2 ).

8. W hen the glue drie s, cu t th e pa vem enta ttache d t o the clot h alo ng t he pr evio usly esta b-lish e d cuttin g lines. I d entify th e fragm e nts and the m o saic pa nels wit h letters and num bersa ccordin g to the p lan.

92



Fig. 3 - A cem ent m ortar is ap plied over the m etal f rame -work attac hed to the bac k of t he m osaic

9. Prob e un der the p ane ls w ith lo ng c hise lsin o rder t o separa te the p av emen t f rom th e earth . Sandw ich the p a nel in a woode n framean d the n tu rn it ups ide-d own .

10 . Pa ck as ma ny panel s in to cra tes as po s-sib le an d tra nsp ort t hem to th e wo rks hop.Resto r ation

One can sum marize th e r estor atio n wor k a sfollo w s:

1. R emo ve t he ol d ce men t wit h poi nted tools and c hi sels.

2. L ay out th e pane ls, face d own, o n theg round ac cording t o the or iginal pla n.

3. On to p of t he pane ls, lay a w ire me sh reinfo rc ed wit h s ix 10 mm diam et er stee l b ars,accordi n g to the dimensi o ns of the panels.

4. Pin e metal or wood en strips s hould be pl a ced bet w een the panels in order to conta inth e w et ce me nt.

5. T he back of the mo sa ic is th en moist en ed

w ith wate r a nd co ver ed w ith a mi xtur e in t hefo llowing p ro portion s: cemen t 1, grave l 1, sand 2 (Fig. 3).

6. A fter ev er ything is dry, lif t u p the pa nelsa nd turn them fa c e up. D etach th e cloth f r omthe p aveme nt surfac e. Clean th e pave m ent and wash it w ith w ate r. No w t he m osa ic is r ead y tobe disp laye d in the desi red l ocat ion.

7. In t he ch ose n loc atio n, ay the pane ls s ideby side a cc ording to the o rig inal pl an , eithe r o nth e g round or on a wa ll (wh ere they wo uld b eattache d with sm all meta l hooks).

8. Al l lacu nae sho uld be f illed with app ro-p riately c o loured t e sserae o f similar size.

9 3



TH E M OS AI C O F THE G OOD S HEP H ERD

(Th e autho r did n o t furn is h illu s tratio ns ).

I h av e th e h on our of pre se ntin g t o y ou anill us trati on of t he rec on stru ct ion of a 5t h c en-tury A. D . pave ment f ragme nt, disc overed in 189 0in Mon te cilla s, Hue s ca, S p ain. Th is w or k wa s car rie d ou t b y th e Istit uto de C ons erv aci on yResta uracio n de O b ras d e Arte i n Mad r id.

F irst t he fig ur e ide n tifie d as T he G o odS hephe rd wa s stud ied, as well a s the related in s crip tio n. B y mea n s of se ver al lette rs stil lvisib le , we re cons tr ucted the w o rd a d ornav it .

In t he sli d es, w e can s ee:T he da mag ed are a s of th e m os aic b ef ore

work b egan. P rep ara tory d raw ing s fo r th e re co nst ruc tion

of t h e figu re.P repa ra tion o f the su ppor ting pa n el wi th the

use of Ara ldi te.

R esin i s add e d.V ie w of th e fib r eglas s .

Rolling the m osaic, the tes serae becom e at-ta ched t o the s uppor t.

Th e fig ur e w as reco n struc te d wi th tess er aefound in si tu Th e bor der wa s finis hed w ithdeta ch ed fr ag men ts from the o rig inal w ork. Fo rth e lette r s of t h e ins c riptio n ado r navit , andfor t he blue a nd g ee n ba c kgrou n d, we u sed te s-

by J e ronim o Esca lera Ur e na

O r igina l text i n Eng lis h

serae of a p lastic m ateria l colou red wi th spec ialm inera l pigm e nts. T h ese te ssera e were used t o obtai n colo ur s wh ic h wo ul d mo s t clos e ly ble n dw ith th e orig in al tes s erae .

The fin ishe d p ane l. L acun ae in t he figu re were fill e d wit h a dra wing

A t p res ent, th e pa ne l wi th i ts w oo den fra me is on d isplay in the Archa eologi cal Mu seum ofH uesca .

D ISCU S SION

M. B assie r : Can y ou t el l us h o w yo u mad e syn thetic tesser a e?

Sr. Es calera Uren a: We have s evera l syn-thet ic elem e nts A fter e x perim entin g with v a-

rio us ma teri als , w e h ave tr ied to use th em ins uch a way th at yo u can te ll the y are m oder n. T h e mo sa ic pi ec es a re mad e of A ra ldite, m ixed wit h pigm e nt in th e m ou ld. It is eas y to cr e atea wid e rang e of c ol ours s imila r to tho s e fou n dlin Ve nic e o r R om e. I th ink it's int ere stin g b e-cause it is h ard to find m ateria ls res emblin gth e or ig inal on es. Sy nthe tic sub s tanc es see m diff e rent, w arme r to the touch of the hand .

94



F ig. 8 - T he G rea t Pa v em e nt, W oo dch e ste r . Th e su rfac e ha s be en c ove r ed w ith s crim fol lowin g th e pa ttern line s,

A se ct io n ha s be en c ut o ut an d lif te d. T he ri uc le us h as b ee n de ta c he d, d isc lo si ng a fr ac tu re in th e b as e

a nd thic k. T he pav ing ha d co llap sed in t o th e

h ypo c au s t. N o m os a ic w as fou nd in th e tr e nc h so it m us t ha ve fall e n in w hile th e vi lla w as still occ upi ed.

Th e S e a G od mos aic from Ca rtha ge w as also re b ac k ed f or d isp la y in T h e B ritis h M u se u m . T h eo rig in al p an e l w a s ve ry he a vy ab o ut 1 8 0 m m th ick . Th e ne w p a ne l is a bo u t 8 0 m m t h ick a n d

o n e-q uar ter th e w eig ht. T he bac k o f the mo sai c w a s cle a ne d a fter th e o ld b ack ing w as rem ov e d,t he n do p e d w it h ep o xy r e si n. A n a lum in iu m

fr am e w a s p rep a re d an d b e dd e d on to the ba ck o f th e m o sa ic . T h e s pa c es i n th e fra m e w h ic hwer e sp ann ed by r ein forc eme nt n et w ere th e n

fil le d in w ith a m ix tu re o f ep o xy r es in a n d ve r -m ic u lite th u s f o rm ing a n e xtr e m e ly st ro n g b u tlig h t p a ne l.

The las t ex am ple is o f the Gr eat Pav em e ntc f W oo d ch e st e r a n d s h ow s h o w c ert a in re pa irsw e re c ar ri ed ou t wh e n th e p av e m e nt w as un -co v ere d a few ye a rs a go . It i s e x po s ed ev e ry

ten yea rs. T he old m or tar i n th ese sec tion s w a sr e mo ve d an d a ne w b ed u se d to ref ix a rea swh ic h h ad b ec o m e un s ou n d F ig . 8 ).

l w elc ome co mm ents on the se a ctiv ities and I a m w illin g to a n sw e r qu e st io ns t o fu rt he r e x-p lain any de tails .

9 7



acanthus mosaic. The slide on the right, a viewfrom the east, shows most of the acanthusmosaic after cleaning. The borders of the mosaicin the slide on the right were beneath thebedding in the slide on the left at the pointwhich I indicate. The existing strips of mosaicin the slide on the right correspond to theselines in the slide on the left. The threshold inthe slide on the left remains in situ in the slideon the, right.

The lifting of the mosaic was accomplishedby the carpet method in the existing strips andsections. The problem of cleaning was twofold.First, most of the floor had to be cleaned gentlyand carefully in order to uncover the tesseraewhich were still in their original arrangementand leave the remaining disturbed tesserae intheir places with the hope of obtaining an ideaof the former arrangement. On the other hand,

the existing areas of the border were coveredby a very hard, compact grey mortar whichobscured the pattern and colours of the tes-serae. These areas needed more radical treat-ment.

The next slide on the left is a detail of astrip surrounded by the disturbed tesserae mixedwith the mortar, after cleaning. The position ofthe mixed tesserae made it necessary to goextremely slowly using dental tools and softbrushes. In other places, the arrangement ofeight or ten tesserae was only apparent afterthis cleaning. An area of the border which wascovered with mortar is shown on the right.Notice how the tesserae are obscured andadhering together. These areas were cleanedwith various abrasives and instruments. Scal-pels, dental tools, and knives were effective inplaces. For larger areas, the Tunisian workmensuggested two methods which were tried. Thefirst was to rub the area of the mortar withlumps of the local Amilcar sandstone, a coarse,loosely packed rock which acted like sandpaperand wore down with use. We used it both wetand dry. The other suggested method was rubb-ing with wet beach sand. Our success with thesewas limited. We then tried steel brushes, steel

wool, and hammer and wood chisels. With prac-tice, the hammer and chisel would pop off themortar leaving the tesserae clean and separated

from each other, sometimes in blocks. Since thistechnique is quite drastic, it was used to deter-mine the colours only. The single uncovered tes-serae in the slide on the right were cleaned thisway. The combined abrasive techniques servedto clean the sections well enough so that theycould be lifted. The PVA adhered well to themortar.

The last pavement which I will discuss wasuncovered during the 1977 season in the peri-style house. It is shown in these two slides - theone on the left illustrates its present situationbetween excavated areas. Its fragmented stateis clearly visible as is its precarious situation.The mosaic appeared early in the season. Scien-tific excavation techniques which demand ac-curate recovery of information dictated the treat-ment of the mosaic. Later intrusive robbingpits - where early walls had been - were ex-

cavated first, since this procedure is necessaryfor accurate dating. At the end of the season,the mosaic was left standing up on an islandof stratified material which represents a seriesof occupation levels which will be excavatedin 1978. One was faced with a dilemma. Either(1) leave the exposed, uncleaned mosaic in situover the winter and risk its deterioration, or (2)clean and lift the mosaic and risk losing somearchaeological evidence for its dating, or (3)clean and document the mosaic. consolidate thesurface, and put a layer of earth over it. Sincea watchman guards the site during the winter,and since we had been successful with a similartreatment in 1976, we chose the last option.First the surface of the mosaic was cleaned.It was coated with a tough, compact ayer ofcalcareous soil which yielded only to scrapingwith a scalpel or scrubbing with steel wool.After thorough documentation, the surface wascoated with two layers of polyvinyl acetateemulsion and covered with a layer of earth whichwill be renewed as it weathers.

I have presented the three most importantmosaic finds of the current University of Mi-chigan excavation at Carthage, the problems ofconservation which they raised and some solu-

tions. I hope more light can be thrown on suchproblems by a sharing of information at a gather-ing of this sort.

99



ON THE NEED TO TRAIN MOSAIC RESTORERS

Beginning now, a school of restoration mustbe established to train skilled craftsmen towhom one can entrust mosaics without fearthat they will be harmed".

This statement - unfortunately still valid to-day because nothing has changed - is by GiovanniBattista Cavalcaselle. It is taken from the me-morandum letter of 1862 that he addressed toMatteucci, the Minister of Education of the time.In 1863 it was published under the title "Onthe Preservation of Monuments and Works ofArt and the ReForm of Academic Teaching .

It was first reprinted in• Florence in 1870 ina version consisting of the essential chapterswith the addition of some later observationsand an introduction by Francesco Dall'Onoaro.A complete edition was republished in Rome

in 1875.Chapter 14 is devoted to methods of train-

ing mosaic restorers . In it, Cavalcaselle wrote:Before touching a mosaic, the future restorer

should have a perfect knowledge of ancienttechniques .

Reconstruction of an original work in factrequires a profound knowledge of the old tech-niques used to express different tastes. Fromantiquity to the 19th century, the history of mo-saic art shows a remarkable complexity of aes-thetic expression. He adds later:

"Whenever the restorer has to work on a

mosaic he, or another skilled artist, should makea copy of it, that is, a facsimile, containing alsoits lacunae. The restorer should then fill thelacunae, in the imitation mosaic, as he wouldin the original. In this way, the restorer willshow that he knows the style, the characterand the technique of the work which he intendsto restore. Furthermore, this way of workingwill soon provide a collection of examples ofmosaic techniques of all periods and schools.Arranged in historical and chronological order,these facsimiles would make up the teachingmaterial of the school. A professor could givelessons directly from the mosaics or the fac-similes. These courses would be printed, inorder to serve as references for the student.Students would be required to make coloured

by Ciro Robotti

Translated from the French

copies of these models. Later, they would workon actual mosaics, copying the various ways ofworking in antiquity ".

Cavalcaselle thus maintains that manual workcarried out in the studio (after the close studyand copying of examples from different periods)is a necessary prerequisite to the acquisitionof a deep knowledge of mosaics.

For Cavalcaselle, the most important exer-cises for the student were preparing the cartoonand transposing it in the place where the mosaicwill be set; spreading the setting bed; prepar-ing, placing and orienting the tesserae.

Whenever a teacher restores a mosaic, thestudents should climb up on the scaffolding tostudy the original and to see how the masterworks. Where the best examples of mosaics of

different periods and schools are found, mobilescaffolds should be built so that students maystudy the works at close range. Students shouldalso be concerned with the preparation of thematerials needed in their craft, such as colours,vitreous pastes, polishes, etc. The school shouldhave a laboratory in which a professor of chem-istry would give a course of applied chemistryrelative to mosaics".

Finally, Cavalcaselle points out the need toknow the elements of which a mosaic is made:mortar, marble and stones, vitreous pastes, si-nopie. These are necessary to a diagnosis in

cases of deterioration. They are the basis ofappropriate interventions whether for conserva-tion or restoration. Yet mosaics, judging by thematerials of which they are composed, seemalmost indestructible. In fact, they often areattacked by vibrations from traffic, wearing bypedestrians, humidity, plants and micro-organ-isms, the aging of supports, atmospheric pol-lution which slowly but progressively producesgrave damage.

These destructive factors cannot be studiedby traditional methods. Modern research meth-ods must be used, based on physics, chemistry,etc. By determining the reasons for the losses,it will be possible to fight against them in thefuture.

Modern instruction should include training in

100



Mu s eum , Ostia : Marb le bas -relief show in g cra ftsme n cutti n g tes s erae

th e his to ry a nd c o nno isseu rship of m osa ic s,k no wl edg e of the fu nd am e nta l p rin cip les fo un din th e inte rnat io nal r esto r ation agr e eme nts, a s cien tific k n owl e dge o f the cau se s o f dete r iora -tio n, an d a s y stem atic w ay o f wo rking . Also tob e s ou gh t is m anu al de xte rit y t hro ug h d ire ct an dco nst an t c on tac t w ith th e m a ter ial . It sh ou ld be re me m be re d t ha t si n ce a n tiqu it y a pp ren ti ces we re in th e w o rks ho ps an d lea rn ed th eir cr aft b y w or kin g dir ect ly w ith th ei r m as ter s. Th us the ylea rned to re c ogn iz e th e par t icula r typ e of s u r-fa ce a m osa ic re qu ires a nd ho w to res to re mo -sa ics w hic h h av e nee d of re sto rat ion .

C a valc a sell e' s re co mm e nda tions a re s tri king -ly rel evant today whe n disc ussio ns on the s ubjec ta re b ein g held in It al y a nd in o the r E ur op ea nco un tri es un de r t he au sp ic es of int er nat io nal org a niza tions.

He re we w ou ld like to e xp res s t he wi sh th atth is ass embl y wou ld pr o pose the p rom p t est ab-li sh me nt of sc ho ol s fo r mo sa ic re sto re rs an dwo uld r eco m me n d a ve ry sp eci fic dis c iplin e , in both histo ry an d tec h niqu e. In Italy, the p roblem of tra ining rest o rers has been the subje ct of co n tinu a l dis c uss io n s inc e t he na tio na l a ss em -bly , A F ut ure fo r R es to rat ion , wh ich w as he ld

fr o m th e 23 rd to th e 26 th of S ept e mbe r 197 6 inN ap les a nd R av el lo. In th e gro up A r ts a n dCr aft s i n. R e sto ra tion , the p rob le m of pre se rv-ing a rchi te ctur a l pro p ertie s (m a rble d eco ra tion s ,pla st er, wo o d, e tc .) w a s p art icu la rly dis cu ss ed. T he fin al re sol ut ion of th e m e eti ng st ate s tha tth e ir p re ser v atio n dep e nds o n th e re co gni tionof t he la ck of re sto ra tio n t ec hn ici ans t rain e din the ri go rou s sc ien tif ic m e tho d s o f t his pr o-fe ss ion .

Wh a t is n eede d is a chan ge in ment a lity. T hismus t beg in at th e p rim ar y or s e con da ry l e vel o f e duca tion i n wh ich, u p to t oday , eve r ythin g isgea red t ow ard crea tion a n d n ot hing t owa rd co n -se rva tio n.

C o nclu ding this b rief addr e ss i n a fi e ld in whi ch Vt iollet- le-Duc , Rus kin, C avalc asell e, Bo itoand Beltr a mi - to nam e on ly som e of the g reate s tt heor e ticia ns a n d pr a ctic ti oner s - h a ve d istin-gu ished them selv es, w e wo uld lik e to expre ssthe wish that a co u rse f o r m o saic ' tech n icia n sbe e s tabli s hed a s ra p idly a s po s sible . Ifs a vas t and com p lica te d ar e a w h ich n eeds not o nly t h e

com m itm e nt of a q ua lifie d tea m of • p ro fes so rs an d ex perts but a lso ad equa te fun ding from thegov e rnme nt.

1 0 1



ES T AB L IS HM E NT O F A N IN TE R NA T IO N AL C O MM IT T EE F O R TH E C ON S ER V A TIO N O F M OS A IC S

In o rd e r to c on tinu e the wo rk w h ich h as b eg u n w ith t h e F ir st In ter n atio n al S ym p os iu m o n th e C onse rvati on o f Mo saics , a C om m itte e ha s be e n fo rme d . Th e m e mb e rs o f the Boa rd a re th e foll owin g:

T h e D irec tor o f IC C RO M ( e x o fficio ) or h is re pre s en tativ e sH en r i L av ag n e o r a re pr es en ta tiv e of A IE M A (e x of fic io) Irin a A nd re es cu Cla ude B as s ierM o ngi Enn a ifer La wre n ce M aje wsk i Pao lo M o raW illiam E. N ovi s M ari a Lu is a V e loc c iaA lb er to V illa Ro lf W ih r,

ICO M , I C OM O S a nd IIC w ill b e inv ited to se n d o b se rv ers . Th e Co m m it tee w ill w or k in co nt ac t w ith t h e I nt ern a tio n al A s so c iati on fo r th e Stu d y o f An tiqu e

M o sa ic s ( A IEM A ) a n d w ill s e ek, to d et erm ine a rea s of c oop e ra tio n w ith th e A s so ci atio n .Coll a bor a tion with UN E SC O, IC OM , ICO MO S an d IIC will be in ves tigate d. D r. Fe ilde n wil l disc uss

p o ssi b ilitie s w ith th e or g ani z atio n s, w ith the p arti c ula r goa l of s har in g i n form atio n a n d c o ord in ati n gpr oje c ts.

ICC R O M ha s ag re ed t o s e rve a s t he C o mm itte e's S e cre ta ria t un til No v em b er 19 78 .P a olo Mor a ha s be en e lecte d Pr esid ent o f th e Bo ard.

T h e C om m itte e ha s de c ide d on t he fo llo w ing g oa ls :1. Pu b lic at ion , in F ren c h a n d E n gl is h, o f th e pro c ee d ing s of th e S ym p osi u m. 2. C o llec tion o f s u gg es tio n s f or a fu tur e co u rse o n th e c o ns e rva tion o f m o sa ic s w ith t h e v ie w

to es tabl ishin g a p rog ram. 3 . Esta blish men t of an a nnu a l dir ecto ry o f peo ple w ork ing o n th e co nser vatio n of mos aics .4. Rec omm end atio n, w hen a m o sai c is g oin g to b e d etac hed , tha t a c omp lete cros s-se ctio n

(s tat u me n , ru d us, nuc le us , and tes s era e ) be pre s erv e d.5 . En cou r age men t of the docu me n tati on o f sp ecifi c ca ses of d e stru ctio n, s a lva g e, a nd r e-

s tora tion . A se c on d m e et ing of th e B oa rd to o k pl ac e fro m 6 - 8 J u ly 1 97 8 at T un is a n d Ca rt h ag e

a t t he i nv ita ti on o f t he I ns tit ut n at ion a l tu n is ien d a rt e t d a rc he ol og ie D u rin g th e m ee tin g , t he q ue s tion s inv o lve d in t he s afe g ua rd of m os a ic w ere stu d ied . The ad va nt ag es o f d iffer e nt s u pp o rtsw e re a lso c om p a re d. Th e pr oc e ed in gs o f t he m e et ing w il l b e pu bl ish e d un de r th e t itle : M os ai cs ,N o . 2, Safe gua rd.

1 2



PR E SS R EL E AS E

A t th e en d of the mee ting , the Se c ret a riat sen t to t he p rinc ipal Itali a n n ews pap e rs, and to

th e ne w s s e rvi c es, th e f o llow ing p res s re le as e in E ng lis h, F ran c h a n d I ta lia n :Fif ty sp eci a list s fro m s ixtee n co unt ries hav e me t in Rom e t o dis cus s th e co nser vati on o f

mo s aic s in t he c oun t ries of t h e a n cie n t R o ma n em pire .

The y ar e co n cer n ed a bou t the gre a t da n ge rs pa v em e nt m osa ics a re s u ffer ing f rom the d ama ging

effe cts o f ne w co nstr u ctio n , e x cav a tion , an d en g ine e ring pro jects . Th e y a ls o w ant to em pha size tha twa ll mo saic s ar e en d an g ere d as w ell by p ollu tion a nd b y th e de cay of th e w a lls b ehi n d th e m.

T h ese dan gers are even mo re a c ute beca use few spec ialis ts ar e ca pabl e of cond uctin g p rojec tsto co nser ve, c ons o lida te an d re store mo saic s.

B esid es, la ws pro tecti n g a cou n try s cu ltura l pat r imo n y a re n o t al w ay s ap p lied and , in c erta inco unt r ies, m or e th a n 5 °° o f t h e m o sa ic s ar e d e st ro ye d up o n d is co v ery .

A s a res u lt, t h e m e eti n g d e cid e d:

T o aw a ke n re sp on si ble a g en cie s an d pe rs on s to th e da n ge rs th re ate n ing m o sa ic s.T o fo r m a n n t ern a tio n al C o m m itte e fo r the Co n ser v atio n o f Mo s aic s wi th th e Se c ret a ria t at

ICC RO M .To c reat e a c our s e fo r tec hnic ians res p on s ible for the c ons e rva tion o f m osai c s.S ixt ee n c o un tr ies w ere rep re se n ted : Alg e ria, B elg iu m, B ulg a ria , Cyp rus, E ng la nd , Fra n ce, H oll a nd,

Isra e l, Ita ly, J orda n, S pain , Tun isia , Uni ted S tate s, V atica n Ci ty, W est Germ any , Yu gosl a via.

Thi s firs t sym po s ium wa s he ld fro m 2 to 5 Nov emb er 1 977 at th e In tern a tion al C entr e fo r the S tudy of th e P rese rvatio n an d th e Re stor a tion of C ultu ral P rope rty ( ICCR OM ), 13 Via di S a n M iche le,0 0 153 R om e. T e leph one s : 58 -94-7 4 1 / 5 8-0 9 -02 1 .

1 3



ONTENTS

INTRODUCTION

P. 3 Acknowledgments

5 Foreword

6 ources of illustrations

7 ist of participants

13 lossary

Bernard M. Feilden

OFFICIAL PAPERS

P. 5 The Conservation of Pavement Mosaics Before Modern Times:A Selection from the Mosaics of Gaul Henri Lavagne

20 The Wall Mosaic: istory of Restoration, Evolution of Tech-niques Irina Andreescu

37 Discussion

39 Conservation Problems of Mosaics in Situ Maria Luisa Veloccia

46 Discussion

47 Some Experiments in the Use of Epoxy Resins for the Impre-gnation of the Nucleus Giuseppe Marinelli

49 The Removal of Weeds from Outdoor 'Mosaic Surfaces Alberto Villa

52 Discussion

54 The Cleaning, Consolidation and Treatment of Wall Mosaics Lawrence Majewski

61 Discussion

62 The Restoration of Mosaics in Gefmany Rolf Wihr

67 Some Problems in the Conservation of Mosaics Claude Bassier

78 Appendix

81 Discussion

83 The Problem of Lacunae in Mosaics Paul Philippot

ADDITIONAL PAPERS

P. 90 The estoration nd onservation f osaics n Tunisia Mongi Ennaifer

91 The Activities of the Department of Antiquities of the Hashe-mite Kingdom of Jordan Mohammed Ghouj

92 The reatment f osaic avements in Syria ince 1939 Raif Hafez

94 The Mosaic of « The Good Shepherd Jeronimo Escalera Urena

95 The Treatment of Some Mosaics in England William E. Novis

98 The Treatment of Mosaics at Carthage Amy Rosenberg

100 On the Need to Train Mosaic Restorers Ciro Robotti

FOLLOW-UP OF THE MEETING

P. 102 stablishment of an International Committee for the Con-servation of Mosaics

103 ress release

1980 mosaics 1 rome eng 8622 light

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