MATERIALSINFORMATIONandTECHNICALRESOURCESforARTISTS-RigidSupports

Thereareprosandconstoallsolidandflexiblesupports.Generallyspeaking,anidealsupportwillbeabletowithstandfluctuationsinRHandtemperature,possessanadequatelevelofabsorbencyand/ortooth,remainplanarandresistwarping,andnotbecomebrittleorfragilewithage.

Onedrawbackoftenassociatedwithflexiblesupportsisthattheyaremoresusceptibletobeingdamagedbyphysicalimpact(e.g.tears,impactcracks,punctures,etc.)Flexiblesupportsmadefromcelluloselikecottonandlinenaremorelikelytorespondtochangesintheenvironment,givingrisetodrawsinthecorners,anoveralllossoftension,andotherplanardeformations.Suchdamagescanleadtobothshortandlongtermconditionissuesandcanaffectthestabilityofthepaintandgroundlayers.Becauseoftheseissues,artistsarehighlyencouragedtoaffixprotectivebackingboardstothereverseoftheirpaintings.Thishelpstopreventphysicalimpactsfromthereverseandhelptobufferandslowthefabric’sresponsetochangesinhumidity.

Rigidsupportsmadefromhygroscopicmaterialslikewoodarelesslikelytowithstandphysicaldamagebutwillstillreacttochangesintheenvironment(e.g.warping,cracking,etc.)whichcanadverselyaffectthegroundandpaintlayers.Therearestepsthatartistscantaketomitigatesomeoftheseproblems.Onemethodistoadhereafabricsupportoverthefaceoftherigidpanel.Thefabriccanserveasalessbrittleinterlayerwhichmaystopthecrackorsplitfromtelegraphingfromthesupporttothegroundandpaintlayersshouldtherigidsupportexhibitwarpingand/orcracking.Rigidsupportscanalsobecradledorbraced,particularlyiftheyarelargeinsize,tocounteractpossiblewarpingorothertypesofplanardeformations.RIGIDSUPPORTS

Manydifferentsolidsupportmaterialsareavailabletoartists.Thesematerialsincludewood,metal,andmoderncompositematerials.Asthereareprosandconsassociatedwithanychoiceofsolidsupport,artistsshouldkeepinmindthesize,ground,andpaintlayersthatwillbeappliedwhenselectingandpreparingtheirsubstrates.Thefollowingisinformationaboutanumberoftypesofsolidsupportsthatarecurrentlyavailabletoartists. Additionalinformationonhistoricalandcontemporarypracticesrelatingtorigidsupportsisavailableinthesectioncontainingonlineresourcesandreferences. SolidWoodPanels

Forcenturiespaintershaveusedhardwoods(fromdeciduoustreesandnarrow-leavedevergreens)andsemi-hardwoods(partiallymaturedcuttingsfromdeciduoustrees)includingoak,mahogany,chestnut,andpoplarhavebeenusedas

supports.Thelong-termageingpropertiesofsolidwoodpanelsdependonthetypeandcutofwood.Sapwoodistheoutermostportionofatreetrunk(thelivingpartofthetree),whileheartwoodisthetrunk’sinner(dead)core.Heartwoodismoresuitableforuseforpaintingsupportsasitshrinksandswellslessthansapwood.Allsolidwoodpanelsaresusceptibletosomedegreeofwarping,shrinkageorexpansion.Thiscanbelessenedbytheselectionofthemoreappropriatecutsofwood(radialratherthantangential),properpreparation(ageinganddrying)ofthewoodensupport,andthemethodoftreatment(finishingbothsidesofthepanelinasimilarmanner).Sometypesofwoodaremorelikelytoexperienceattacksbywood-boringinsects.Thisshouldbetakenintoconsiderationwhenselectingandpreparingawoodensupport.

Thestabilityofawoodenboardisgreatlyinfluencedbywhereitwascutfromtheoriginaltreetrunk.Woodexpandsandcontractsinthedirectionperpendiculartothegraindirection.Woodenboardstendtobemoststablewhentheyaremostsimilaronthefrontandback.Tangentiallysawnplanksarepronetoplanardeformationslikewarping,splitting,andcrackingastheseplanksoftencontainbothsapwoodandheartwoodandthenumberofgrainlinesareverydifferentonthefrontascomparedtotheback.Radiallysawnplanksaregenerallymorestable.Whenapanelsupportiscomprisedofmultipleplanks,theorientationofthewoodgrainhasaneffectonthestabilityofthepanel.Ifthegrainofadjoiningplanksisorientedperpendiculartooneanother,structuralproblemscanarisewhenthesupportexperiencesenvironmentalfluctuations.Therefore,ifmultipleplanksaretobejoinedtogether,alloftheplanksshouldhavethewoodgrainorientedinthesamedirection.Supportscreatedfrommultipleplankscandevelopsplitsandcracksalongthejoinswhensubjectedtoadverseenvironmentalconditions,andtensionbetweenthesectionsofthewoodcanresultincrackingorsplitting.Artistswhoworkonalargerscaleshouldkeepthisinmindwhenselectingand/orpreparingwoodenpanelsupports.

Whenartistsusewoodensupports,theyshould: • Consideringusingwell-seasonedhardwoodslikemahogany,maple,or

oak.Inspectthesurfaceofthepaneltoensurethatnoknots,cracks,orotherdeformationsarepresent.

• Useplanksthatareatleast2.5cm(1”)thick,asthinnerboardsaremorelikelytosufferstructuraldeformation.

• Avoidsemi-hardwoodsandsoftwoodslikepoplarandpinewhenpossible.Ifthesewoodsarechosen,itisrecommendedthattheybecoveredwithalayerofcanvastopreventthetransferofsplitsandcracksfromthesupporttothegroundandpaintlayers.Largerformatwoodensupportscomprisedofmultipleplanksshouldalsobecoveredwithcanvas(overallifpossibleoratleastusecanvasstripstocoverjoins/splits)tohelppreventthetransferofsplitsandcracksfromthesupporttothegroundandpaintlayers.

• Considersizing(andpossiblypriming)bothsidesofthesupportinordertomitigatepotentialwarpinginthefuture.Thisprocedureensuresthatbothsidesofthepanelwillrespondmoresimilarlytoenvironmentalchanges.PossiblesizingmaterialstoconsiderincludeneutralpHPVA,certainacrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels),andvarnishcoatings(e.g.Regalrez1094,MSAvarnishes,etc.).Refinedshellacandpolyurethanecoatingshavealsobeenusedtoeffectivelyreducetheabsorbencyofthesurfaceandtosealthewoodbutartistsshouldtakecarenottoapplythesematerialstoothickly.Shellacandpolyurethanearelessthanidealmaterialsintermsofreversibility,brittlenessandagingcharacteristics.

• Support-induceddiscoloration(SID)couldoccurifwater-solublematerialsmigratethroughthesize/sealantandsubsequentlystainthe

groundand/orpaintlayers(water-solublefractionsoftenincludetannins,starch-basedmaterials,etc.).TopreventSIDfromoccuring,considerapplyinganevencoatofneutralpHPVAadhesiveoracrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels)tothesurfaceofthepanelpriortoapplyingacrylicgrounds,oilgrounds,orfabric/paperinterleafs.Toadherecanvas/papertoapanel,thefollowingstepsarerecommended:

ApplyoneevencoatofPVAsizeoracrylicgelmediumtothesurfaceofthepanelusingaspatulaorabrush.Lightlywetthereverseofthecanvas(thesidethatwillbeadheredtothepanel)withwatertopromotebetteradhesion.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).ImmediatelyapplyanothercoatofPVAsizeoracrylicgelmedium(sticktothesamematerialyouusedpreviously)tothefaceofthecanvas.Oncethecanvashasdried,applyacoatofPVAsizeoracrylicgelmediumtothereverseofthepaneltopreventpotentialwarping.

• ItisalsopossibletouseBEVA371adhesive/filmtoadherecanvasto

panelafterthepanelhasbeensealed.BEVAfilm(asopposedtotheadhesive)willnotpenetratethefabricsupportasreadilyasPVAadhesiveand/oracrylicmediumsmightandtheabilitytore-activatetheadhesivemakesitfareasiertoeliminateanyunwantedair-bubbleslateronshouldtheyformduringtheprocess.Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:

ApplyonetotwoevencoatsofdiluteBEVAadhesive(thincreamconsistency)tothepanelaftercleaningthesurfaceandtwocoatstothereverseofthecanvas(wearadequateprotectionassolventsarerequired).IfyouareusingBEVAfilmitisbettertousetwosheetsoffilmasopposedtoone,althoughonesheetmaybeabletoprovideenoughadhesion.PlacethefilmwiththeBEVA-sidefacingthepanel(orcanvasifyouareusingtwosheets)withoutremovingthesilicone-coatedMylarandapplyheatevenlyusinganiron(BEVAadhesiverequiresatemperatureofaround65.6degreesCelsiustobere-activated).WeightdownthesurfaceuntiltheBEVAhascooledandthencarefullypeelawaythesilicone-coatedMylar(NOTE:IfyouattempttoremovetheMylartoosoonyouwillpulluptheBEVA).Ifyouareusingtwosheets,repeatthisprocesswiththeothersheetofBEVAfilmwhenapplyingtothereverseofthecanvassupport(considerplacingsilicone-releasepaper/Mylarbeneaththecanvaswhenapplyingheat,siliconesidefacingup).ThenpositionyourcanvasdirectlyatoptheBEVAfilm,

placesilicone-releasepaper/Mylar(siliconesidefacingdown)atopthecanvas,andapplyheat.IfyouareusingBEVAadhesivesimplywaitforthecoatsofBEVAtodry(inawellventilatedspace)andrepeattheaforementionedstep.IfyouexperiencedifficultiesusingBEVAfilmtryapplyingacoatofadhesivetothebackofthecanvasorswitchtotheadhesivealtogether.

Considerusingatemperaturecontrolledvacuumtableifyouwishtoadhereacompletedpaintingontoapanel.Ingeneralthisisnotrecommendedandheat/pressureshouldbeavoidedentirelyifthepaintfilmisstillfairlyyoung.Itmaybepossibletosafelyadhereyourcompositionifitdoesnotcontainthicklybuiltuppaint,wax-basedadditives,orareasofstrongimpasto.Followtheinstructionsabovebutconsiderusingasoftblotterpaperoveryoursiliconereleasepaper/Mylartoprotectmoredelicatesurfaces(youmayalsoneedtoraisethetemperatureofyourironeversoslightly).

• Althoughrabbitskin/animalgluepossesseshygroscopicproperties,

manyartistscontinuetousethistraditionalmaterialasasizeand/oradhesive.NotethatitisNOTadvisabletoapplyacrylicand/orPVAsizetohardboards/fiberboardspriortoapplyingtraditionalglue-basedgessogroundsasthiscouldleadtopotentialdelamination.ToavoidanyissuesrelatingtoSIDhowever,artistsshouldconsideradheringfabrictothepanelsupportpriortoapplyingthegessoground.Toadhereyourcanvastoapanelusinganimalglue,thefollowingstepsarerecommended:

Prepareyouranimalgluefollowingthedirectionsonthepackage.Brushagenerous,evencoatofglueontothepanel’ssurface.Youmayallowthiscoattodrybeforecontinuingwiththeprocessorproceedimmediately.Wearingnitrilegloves,immersethecanvasintothetepidglue(makesurethatitisnotsohotastoburnyourhands),gentlywringthefabrictoremoveexcessglue.Positionthefabricontothepanel.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).Immediatelyapplyacoatofgluetothereverseofthepanel(NOTE:Itisnotadvisedtoleaveacoatofanimalglueexposedtotheenvironment.Subsequentlayersofprimingandpaintneedtobeappliedtothereverseinordertoavoidwarping,mimickingthesamelayeringusedonthefrontofthepanel).Allowforadequateandevendryingbystandingthepanelonitsedgeorleaningagainstawall.

• Provideadditionalauxiliarysupporttolargeformatpanelsandpanelsthatarelessthan¾”thickbyattachingabraceorcradlebygluingstripsofwoodaroundtheoutsideedgeofthebackofthepanelusingthefollowingsteps:

Obtain1”by2”woodenboards(oakormaplearepreferred)andcutthemdowntomatchtheouterdimensionsofthesupport(overallsizewilldependonwhattypeofjoinisusedforthecorners).Buttandmiteredtendtobethemostcommontypeofjoins(considerusinga90degree-cornerclampwhenmakingmiteredcorners),howeverlapjoinsaregenerallyconsideredtobemorestructurallysound.Makesurethatthewoodenboardsareperfectlyalignedandflushwiththeouteredgesbylayingthemonthereverseofthepanelbeforegluingtothereverse(itcanhelpfultomarkthepositionwithapencil).Usecarpenter’sgluetoadherethewoodenboardsinplaceWhiletheglueisdrying,clamp/weighttheboardstoavoidcreatinganyairbubbles.Forlarge-scalesupportsartistsmaychoosetoconstructhorizontaland/orverticalcrossbarsalthoughcrossbarsshouldNOTbeglueddirectlytothereverseofthepanel,onlyfixedtotheouterboardsofthecradleusingglueand/orhardware.

Plywood

Plywoodisalaminatedwoodproductthatispreparedbyadheringtogetherlayersofthinwoodveneer(plies)withthegrainofeachlayerpositionedatrightanglestothegrainoftheprecedinglayer.Sometypesofplywoodareavailablewithalumber,orsolidwood,core.

Diagram showing the alternating directional grain of a 5-ply, wooden

support. Some types of plywood are also available with a solid wood core.

Thecross-laminatestructureofplywood--particularlyifthepliesareallof

equalthickness--helpsensurethatthesupportislesspronetoplanardeformation.Plywoodcanbemadefromavarietyofsoftandhardwoods.Thelattertendstobemoredimensionallystable.Ingeneral,themorelayers,themoredimensionallystabletheplywoodsupport.Exterior-gradeplywoodhassuperiorresistancetomoisture,whileinterior-gradeplywoodhasthesmoothestsurfacefinish.

GatorfoamboardorGatorboardisnotplywood.itiscomposedofextrudedpolystyrenefoambondedbetweentwolayersofwood-fiberveneer.Itprovidesaveryrigidsurface,butthewood-fiberlayersmayrespondtochangesintheenvironment.

PlywoodandespeciallyGatorboardpanelsarenotconsideredsufficientlystableforpermanentuse.Artistsmaybeabletomitigatesomeoftheproblemsassociatedwiththesesubstratesbyconsideringthefollowingrecommendations:

• Inspectthesurfaceofplywoodtoensurethatarenoknots,cracks,or

otherdeformations.• Choosemaple,walnut,ormahoganyplywoodwhicharemoredurable

andstable(birchplywoodcanalsobeused,butthegrainhasatendencytotransferthroughtothegroundandpaintlayersovertime).

• Forlargerworkschooseplywoodthatisatleast¾”thickasthisexhibitsadequatedimensionalstability.

• PlywoodcanandGatorboardpanelsmaybenefitfromadheringafabriclayertothesurfacebeforepriming.Thesepanelsshouldbestoredflat.

• Considersizing(andpossiblypriming)bothsidesofthesupportinordertomitigatepotentialwarpinginthefuture.PossiblesizingmaterialstoconsiderincludeneutralpHPVA,certainacrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels),andvarnishcoatings(e.g.Regalrez1094,MSAvarnishes,etc.).Refinedshellacandpolyurethanecoatingshavealsobeenusedtoeffectivelyreducetheabsorbencyofthesurfaceandtosealthewoodbutartistsshouldtakecarenottoapplythesematerialstoothickly.Shellacandpolyurethanearelessthanidealmaterialsintermsofreversibility,brittlenessandagingcharacteristics.

• Support-induceddiscoloration(SID)couldoccurifwater-solublematerialsmigratethroughthesize/sealantandsubsequentlystainthegroundand/orpaintlayers(water-solublefractionsoftenincludetannins,starch-basedmaterials,etc.).TopreventSIDfromoccuring,considerapplyinganevencoatofneutralpHPVAadhesiveoracrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels)tothesurfaceofthepanelpriortoapplyingacrylicgrounds,oilgrounds,orfabric/paperinterleafs.Toadherecanvas/papertoapanel,thefollowingstepsarerecommended:

ApplyoneevencoatofPVAsizeoracrylicgelmediumtothesurfaceofthepanelusingaspatulaorabrush.Lightlywetthereverseofthecanvas(thesidethatwillbeadheredtothepanel)withwatertopromotebetteradhesion.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).ImmediatelyapplyanothercoatofPVAsizeoracrylicgelmedium(sticktothesamematerialyouusedpreviously)tothefaceofthecanvas.Oncethecanvashasdried,applyacoatofPVAsizeoracrylicgelmediumtothereverseofthepaneltopreventpotentialwarping.

• ItisalsopossibletouseBEVA371adhesive/filmtoadherecanvastopanelafterthepanelhasbeensealed.BEVAfilm(asopposedtotheadhesive)willnotpenetratethefabricsupportasreadilyasPVAadhesiveoracrylicmediumsmightandtheabilitytore-activatetheadhesivewithheatmakesitfareasiertolateraddressanyunwantedair-bubblesshouldtheyformduringtheprocedure.Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:

ApplyonetotwoevencoatsofdiluteBEVAadhesive(thincreamconsistency)tothepanelaftercleaningthesurfaceandtwocoatstothereverseofthecanvas(wearadequateprotectionassolventsarerequired).IfyouareusingBEVAfilmitisbettertousetwosheetsoffilmasopposedtoone,althoughonesheetmaybeabletoprovideenoughadhesion.PlacethefilmwiththeBEVA-sidefacingthepanel(orcanvasifyouareusingtwosheets)withoutremovingthesilicone-coatedMylarandapplyheatevenlyusinganiron(BEVAadhesiverequiresatemperatureofaround65.6degreesCelsiustobere-activated).WeightdownthesurfaceuntiltheBEVAhascooledandthencarefullypeelawaythesilicone-coatedMylar(NOTE:IfyouattempttoremovetheMylartoosoonyouwillpulluptheBEVA).Ifyouareusingtwosheets,repeatthisprocesswiththeothersheetofBEVAfilmwhenapplyingtothereverseofthecanvassupport(considerplacingsilicone-releasepaper/Mylarbeneaththecanvaswhenapplyingheat,siliconesidefacingup).ThenpositionyourcanvasdirectlyatoptheBEVAfilm,placesilicone-releasepaper/Mylar(siliconesidefacingdown)atopthecanvas,andapplyheat.IfyouareusingBEVAadhesivesimplywaitforthecoatsofBEVAtodry(inawellventilatedspace)andrepeattheaforementionedstep.IfyouexperiencedifficultiesusingBEVAfilm,tryapplyingacoatofadhesivetothebackofthecanvasorswitchtotheadhesivealtogether.

Considerusingatemperaturecontrolledvacuumtableifyouwishtoadhereacompletedpaintingontoapanel.Ingeneralthisisnotrecommendedandheat/pressureshouldbeavoidedentirelyifthepaintfilmisstillfairlyyoung.Itmaybepossibletosafelyadhereyourcompositionifitdoesnotcontainthicklybuiltuppaint,wax-basedadditives,orareasofstrongimpasto.Followtheinstructionsabovebutconsiderusingasoftblotterpaperoveryoursiliconereleasepaper/Mylartoprotectmoredelicatesurfaces(youmayalsoneedtoraisethetemperatureofyourironeversoslightly).

• Althoughrabbitskin/animalgluepossesseshygroscopicproperties,

manyartistscontinuetousethistraditionalmaterialasasizeand/oradhesive.NotethatitisNOTadvisabletoapplyacrylicand/orPVAsizetohardboards/fiberboardspriortoapplyingtraditionalglue-basedgessogroundsasthiscouldleadtopotentialdelamination.ToavoidanyissuesrelatingtoSIDhowever,artistsshouldconsideradheringfabrictothepanelsupportpriortoapplyingthegessoground.Toadhereyourcanvastoapanelusinganimalglue,thefollowingstepsarerecommended:

Prepareyouranimalgluefollowingthedirectionsonthepackage.Brushagenerous,evencoatofglueontothepanel’ssurface.Youmayallowthiscoattodrybeforecontinuingwiththeprocessorproceedimmediately.Wearingnitrilegloves,immersethecanvasintothetepidglue(makesurethatitisnotsohotastoburnyourhands),gentlywringthefabrictoremoveexcessglue.Positionthefabricontothepanel.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).Immediatelyapplyacoatofgluetothereverseofthepanel(NOTE:Itisnotadvisedtoleaveacoatofanimalglueexposedtotheenvironment.Subsequentlayersofprimingandpaintneedtobeappliedtothereverseinordertoavoidwarping,mimickingthesamelayeringusedonthefrontofthepanel).Allowforadequateandevendryingbystandingthepanelonitsedgeorleaningagainstawall.

• Provideadditionalauxiliarysupporttolargeformatpanelsandpanelsthatarelessthan¾”thickbyattachingabraceorcradlebygluingstripsofwoodaroundtheoutsideedgeofthebackofthepanelusingthefollowingsteps:

Obtain1”by2”woodenboards(oakormaplearepreferred)andcutthemdowntomatchtheouterdimensionsofthesupport

(overallsizewilldependonwhattypeofjoinisusedforthecorners).Buttandmiteredtendtobethemostcommontypeofjoins(considerusinga90degree-cornerclampwhenmakingmiteredcorners),howeverlapjoinsaregenerallyconsideredtobemorestructurallysound.Makesurethatthewoodenboardsareperfectlyalignedandflushwiththeouteredgesbylayingthemonthereverseofthepanelbeforegluingtothereverse(itcanhelpfultomarkthepositionwithapencil).Usecarpenter’sgluetoadherethewoodenboardsinplaceWhiletheglueisdrying,clamp/weighttheboardstoavoidcreatinganyairbubbles.Forlarge-scalesupportsartistsmaychoosetoconstructhorizontaland/orverticalcrossbarsalthoughcrossbarsshouldNOTbeglueddirectlytothereverseofthepanel,onlyfixedtotheouterboardsofthecradleusingglueand/orhardware.

Hardboards,Fiberboards,etc.

Theterms“hardboard”and“fiberboard”areoftenusedinterchangeablydespitethefactthattheyaredifferentproducts.ThemajordifferencebetweenhardboardssuchasfiberboardpanelslikeMediumDensityFiberboardandHighDensityFiberboard(e.g.Masonite)isthewayinwhichtheyaremanufactured.

Hardboardpanelsaregenerallycreatedthroughawet/dryprocesswhich

reliesonnaturallypresentcellulosiclignininthewoodtocementthefiberstogether.Temperedhardboardsareimpregnatedwithanoilyorresinoussubstancemakingthemdarkerincolor(untemperedhardboardsareusuallyalightbrowncolor)andmoreresistanttomoistureandmechanicaldamage(andthereforesubsequentwarping,raisingoffibers,etc.)thanuntemperedhardboard.Masonite,oneofthemostcommonlymanufacturedhardboards,firstbegantobeusedforartisticpurposesinthelate1920s. Support-induceddiscoloration(SID)couldoccurifwater-solubleand/oroilyorresinousmaterialsmigratethroughthesizeorsealantandstainsthegroundand/orpaintlayers(water-solublefractionsoftenincludetannins,starch-basedmaterials,etc.).Today,mosttemperedhardboardsupportsarelesslikelytocauseSID-relatedissues,howeverartistsshouldconsiderexercisingcertainprecautionstopreventSIDdependingonthevariouspreparatorytechniquesthatareused(refertothelistofsuggestionsattheendofthissection).

Fiberboardpanelsarecreatedthroughadryprocessthatreliesonchemicalagentslikeurea-formaldehydetobindthewoodfiberstogether.HighDensityFiberboard(HDF)issuperiortoMediumDensityFiberboard(MDF)asithassignificantlyhigherinternalbondstrengthandislesssusceptibletomoisturedamage.However,HDFisstillpronetoplanardeformation.Propersealingorsizingandgroundapplicationcanmitigatethisproblem.

Clayboardsarehigh-densityfiberboardsthathavebeencoatedwithalayerrichinclay(kaolin).Becausetheclaylayerservesasastableground,clayboardsare

notpronetosupport-induceddiscoloration(SID).AmpersandArtSupplyisamajordistributorofclayboards(andothersolidsupportsforartists).

Theadvantagesoftheseboardsoverwoodarethattheyareavailableinlargesheets,havenograin(i.e.,nodirectionalmovement),andarenotassensitivetoclimaticchangesorattackbywood-boringinsects.Largesheetsdotendtowarpandtwistandcornerscanbecomebent,compressed,orexpanded.Untemperedhardboardsshouldnotbeusediflong-termpreservationisaconcern.Untemperedhardboardwasoncepreferredovertemperedduetotheearlieruseofsubstantialamountsofoilincorporatedintotheearliertemperingformulationswhichcouldmaketheminappropriateasasurfacetoreceivewatercontaininggrounds.Highqualityhardboardspurchasedfromrespectedsuppliersdonotsufferfromthisdefect. Whenartistschoosetousethesesupports,theyshould:

• Degreasethesurfacewithdenaturedalcoholbeforeapplyinglayersofsize,ground,and/orpaint.Withoutthispreparation,groundlayersmaynotadheretothesmoothsideofthesesupportsbecauseofsurfaceresidessuchasparaffinwaxthatmaybeleftduringthemanufacturingprocess.

• Gentlysandthefaceofthepanelwithfinesandpaper(e.g.220grit)toprovideaslightmechanicaltoothbutbecarefultonotoverlyroughenthesurfaceandunevenlyexposethewoodfibers.Thiscanleadtoirregularswellingofthesubstrate(particularlywhenwater-basedsizes,sealantsand/orpriming/groundareapplied).

• Considersizing(andpossiblypriming)bothsidesofthesupportinordertomitigatepotentialwarpinginthefuture.ThisstepcanalsohelptocounteractSID-relatedissues.PossiblesizingmaterialstoconsiderincludeneutralpHPVA,certainacrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels),andvarnishcoatings(e.g.Regalrez1094,MSAvarnish,etc.).Refinedshellacandpolyurethanecoatingshavealsobeenusedtoeffectivelyreducetheabsorbencyofthesurfaceandtosealthewoodbutartistsshouldtakecarenottoapplythesematerialstoothickly.Shellacandpolyurethanearelessthanidealmaterialsintermsofreversibility,brittlenessandagingcharacteristics.

• ConsiderapplyinganevencoatofneutralpHPVAadhesiveorcertainacrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels)whenadheringcanvas/papertothesurfaceofapanelfollowingdegreasing/cleaningofthesurface(aswithsizingalone,thisstepcanalsohelptocounteractSID-relatedissues).Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:

ApplyoneevencoatofPVAsizeoracrylicgelmediumtothesurfaceofthepanelusingaspatulaorabrush.Lightlywetthereverseofthecanvas(thesidethatwillbeadheredtothepanel)

withwatertopromotebetteradhesion.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).ImmediatelyapplyanothercoatofPVAsizeoracrylicgelmedium(sticktothesamematerialyouusedpreviously)tothefaceofthecanvas.Oncethecanvashasdried,applyacoatofPVAsizeoracrylicgelmediumtothereverseofthepaneltopreventpotentialwarping.

• ConsiderusingBEVA371adhesive/filmtoadherecanvastopanelafterthepanelhasbeensealed.BEVAfilm(asopposedtotheadhesive)willnotpenetratethefabricsupportasreadilyasPVAadhesiveoracrylicmediumsmightandtheabilitytore-activatetheadhesivewithheatmakesitfareasiertolateraddressanyunwantedair-bubblesshouldtheyformduringtheprocedure.Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:

ApplyonetotwoevencoatsofdiluteBEVAadhesive(thincreamconsistency)tothepanelaftercleaningthesurfaceandtwocoatstothereverseofthecanvas(wearadequateprotectionassolventsarerequired).IfyouareusingBEVAfilmitisbettertousetwosheetsoffilmasopposedtoone,althoughonesheetmaybeabletoprovideenoughadhesion.PlacethefilmwiththeBEVA-sidefacingthepanel(orcanvasifyouareusingtwosheets)withoutremovingthesilicone-coatedMylarandapplyheatevenlyusinganiron(BEVAadhesiverequiresatemperatureofaround65.6degreesCelsiustobere-activated).WeightdownthesurfaceuntiltheBEVAhascooledandthencarefullypeelawaythesilicone-coatedMylar(NOTE:IfyouattempttoremovetheMylartoosoonyouwillpulluptheBEVA).Ifyouareusingtwosheets,repeatthisprocesswiththeothersheetofBEVAfilmwhenapplyingtothereverseofthecanvassupport(considerplacingsilicone-releasepaper/Mylarbeneaththecanvaswhenapplyingheat,siliconesidefacingup).ThenpositionyourcanvasdirectlyatoptheBEVAfilm,placesilicone-releasepaper/Mylar(siliconesidefacingdown)atopthecanvas,andapplyheat.IfyouareusingBEVAadhesivesimplywaitforthecoatsofBEVAtodry(inawellventilatedspace)andrepeattheaforementionedstep.IfyouexperiencedifficultiesusingBEVAfilm,tryapplyingacoatofadhesivetothebackofthecanvasorswitchtotheadhesivealtogether.Considerusingatemperaturecontrolledvacuumtableifyouwishtoadhereacompletedpaintingontoapanel.Ingeneralthisisnotrecommendedandheat/pressureshouldbeavoidedentirelyifthepaintfilmisstillfairlyyoung.Itmaybepossibletosafelyadhere

yourcompositionifitdoesnotcontainthicklybuiltuppaint,wax-basedadditives,orareasofstrongimpasto.Followtheinstructionsabovebutconsiderusingasoftblotterpaperoveryoursiliconereleasepaper/Mylartoprotectmoredelicatesurfaces(youmayalsoneedtoraisethetemperatureofyourironeversoslightly).

• Althoughrabbitskin/animalgluepossesseshygroscopicproperties,

manyartistscontinuetousethistraditionalmaterialasasizeand/oradhesive.NotethatitisNOTadvisabletoapplyacrylicand/orPVAsizetohardboards/fiberboardspriortoapplyingtraditionalglue-basedgessogroundsasthiscouldleadtopotentialdelamination.ToavoidanyissuesrelatingtoSIDhowever,artistsshouldconsideradheringfabrictothepanelsupportpriortoapplyingthegessoground.Toadhereyourcanvastoapanelusinganimalglue,thefollowingstepsarerecommended:

Prepareyouranimalgluefollowingthedirectionsonthepackage.Brushagenerous,evencoatofglueontothepanel’ssurface.Youmayallowthiscoattodrybeforecontinuingwiththeprocessorproceedimmediately.Wearingnitrilegloves,immersethecanvasintothetepidglue(makesurethatitisnotsohotastoburnyourhands),gentlywringthefabrictoremoveexcessglue.Positionthefabricontothepanel.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).Immediatelyapplyacoatofgluetothereverseofthepanel(NOTE:Itisnotadvisedtoleaveacoatofanimalglueexposedtotheenvironment.Subsequentlayersofprimingandpaintneedtobeappliedtothereverseinordertoavoidwarping,mimickingthesamelayeringusedonthefrontofthepanel).Allowforadequateandevendryingbystandingthepanelonitsedgeorleaningagainstawall.

• Provideadditionalauxiliarysupporttolargeformatpanelsandpanelsthatarelessthan¾”thickbyattachingabraceorcradlebygluingstripsofwoodaroundtheoutsideedgeofthebackofthepanelusingthefollowingsteps:

Obtain1”by2”woodenboards(oakormaplearepreferred)andcutthemdowntomatchtheouterdimensionsofthesupport(overallsizewilldependonwhattypeofjoinisusedforthecorners).Buttandmiteredtendtobethemostcommontypeofjoins(considerusinga90degree-cornerclampwhenmakingmiteredcorners),howeverlapjoinsaregenerallyconsideredtobe

morestructurallysound.Makesurethatthewoodenboardsareperfectlyalignedandflushwiththeouteredgesbylayingthemonthereverseofthepanelbeforegluingtothereverse(itcanhelpfultomarkthepositionwithapencil).Usecarpenter’sgluetoadherethewoodenboardsinplaceWhiletheglueisdrying,clamp/weighttheboardstoavoidcreatinganyairbubbles.Forlarge-scalesupportsartistsmaychoosetoconstructhorizontaland/orverticalcrossbarsalthoughcrossbarsshouldNOTbeglueddirectlytothereverseofthepanel,onlyfixedtotheouterboardsofthecradleusingglueand/orhardware.

LaminatedPaperBoardsandMuseumBoards

PaperboardsmadefromwoodwasteorwoodpulparesoldunderavarietyoftradenamesincludingUpsonBoardandBeaverBoard.Laminatedpaperboardsshouldbethoughtofastemporarysupports.Theyarehighlyacidicandhaveaweakphysicalstructure,sotheydeterioratequickly.Museumboardisahighqualitylaminatedpaperboardmadeof100%cottonragmatboard.Museumboardshavebetweentwoandeightdistinctlayers.Asmuseumboardlacksstructuralstrength,forincreasedrigidityitshouldbemountedonawoodenauxiliarybraceorpanel.CanvasBoards

Canvasboardsareconstructedfromathinlayerofcottonormuslinprimedwithanacrylicdispersiongroundthathasbeengluedtoasheetofpulpcardboard.Theseboardsshouldnotbeusediflong-termpreservationisaconcern.

Aluminum

Aluminumpanels,AluminumCompositeMaterial(ACM)panels,aluminumhoneycombpanels,andDibondpanelshavebeenwidelyusedbyartistssincethelate1940s.Aluminumismoreresistanttocorrosionthanothermetals,canbecuteasilywithabandsaw,and,dependingonthesizeandthicknessofthepanel,willretainstiffness.Itisnecessarytonotethat,eveninastableenvironment,thinnerpiecesofaluminumwillnotremainplanar.

ACMboardsdifferbymanufacturerbutaretypicallycomposedofathermoplasticcoresandwichedbetweentwolightweightsheetsofaluminum.Theseboardscanbepurchasedwithtwosidesofexposedaluminumandnopreparatorylayer,withacanvasmountedtoonesideandamill(polishedaluminum)finishonthereverse,orwithonesidecoatedwithawhitepolyestercoilfinishtoprotectthesurfaceagainstcorrosion.

ArtefexACMPanelsarecomprisedoftwosheetsof3mmaluminumbondedtoasolidpolyethylenecore.Theycanbepurchasedwithorwithoutapreparatorylayerandwithorwithoutonesidecoveredwithcanvas.DibondACMPanelsare

madeoftwolightweightsheetsof.010”aluminumwithathermoplasticcore.Theyareavailableinavarietyofcolors.

TheadvantagesofACMpanelsoverwoodorstretchedcanvasarethattheydonotrespondasreadilytochangesinRHandarenotpronetoinsectdamage.

Diagram showing the typical layering structure of an Aluminum Honeycomb

Panel.

Diagram showing an example of the layering structure of an Aluminum

Composite Panel (ACM).

Artistswhochoosetousethesesupportsshould:• Preparethealuminum/ACMsurfacesbyremovingtheprotectivefilm.

Degreasingthepresentationside(typicallythesidecoatedwithpolyester)withethanolorisopropanol.Createatooth(e.g.320gritsandpaper)bylightlyrougheningthesurfacewithanabrasivematerialNOTE:Ifawhiteprotectivepolyestercoilcoatingispresentavoidbreakingcompletelythroughitasthisexposestheunderlyingaluminumandcanleadtocorrosion.

• AvoidACMpanelsthatdonothaveapolyestercoilcoating(inindustryACMpanelscanbecoatedwitharangeofmaterials).

• Chooseapriming/groundmaterialcarefully.Priming/groundmaterialsthatareavailableinindustrymaybeacceptableiftheyhavebeenfoundtobecompatiblewithcertainACMbrands(Example:DTMBondingPrimerbySherwinWilliamshasbeenfoundtobehighlycompatiblewithDibondpanels).Aswithmostindustryproducts,artistsareencouragedtotestthesematerialswiththeirpreferredpaintingtechnique.

• FixthinnersupportstomorerigidsupportssuchasMasoniteorconstructacradle(seeinstructionsbelow).Sheetsthataretoothinaremorepronetodamageastheymayflexandtwistduringtransportationandhandling.

• Rememberthat“fatoverlean”principlesshouldbefollowedwhenapplyingalkyd,acrylics,and/oroilpaints.

• UnderstandthatACMpanelswithhoneycomborcorrugatedplasticcores(suchasArtefex)tendtobelighterinweightthanACMpanelsthatcontainsolidplasticcores.

• Avoidsubjectingthepaneltoextremelyhightemperatures(above175F). • Knowthatsupportsthatarefairlyheavyareatriskofplanardeformation

alongtheouteredges(e.g.bentcorners)especiallyduringtransportationandhandling.

• Avoidpaintingdirectlyonthesurfaceofunprimedaluminumasthistechniquecanleadtoadhesionproblems.

• ConsiderapplyinganevencoatofneutralpHPVAadhesiveorcertainacrylicpolymers(e.g.highqualityacrylicdispersionmediumsorgels)whenadheringcanvas/papertothesurfaceofapanelfollowingdegreasing/cleaningofthesurface.Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:

ApplyoneevencoatofPVAsizeoracrylicgelmediumtothesurfaceofthepanelusingaspatulaorabrush.Lightlywetthereverseofthecanvas(thesidethatwillbeadheredtothepanel)withwatertopromotebetteradhesion.Useabrayer/bonefoldertoeliminateanyairbubbles,workingfromthecenteroutwardstotheedges.Ifyouhavedecidedtokeepexcessfabricalongtheouteredges,foldthemoverandattachtothebacksideofthepanel(oraffixthemlater).ImmediatelyapplyanothercoatofPVAsizeoracrylicgelmedium(sticktothesamematerialyouused

previously)tothefaceofthecanvas.Oncethecanvashasdried,applyacoatofPVAsizeoracrylicgelmediumtothereverseofthepaneltopreventpotentialwarping.

• ConsiderusingBEVA371adhesive/filmtoadherecanvastopanelafterthepanelhasbeensealed.BEVAfilm(asopposedtotheadhesive)willnotpenetratethefabricsupportasreadilyasPVAadhesiveoracrylicmediumsmightandtheabilitytore-activatetheadhesivewithheatmakesitfareasiertolateraddressanyunwantedair-bubblesshouldtheyformduringtheprocedure.Toadhereyourcanvastoapanel,thefollowingstepsarerecommended:

ApplyonetotwoevencoatsofdiluteBEVAadhesive(thincreamconsistency)tothepanelaftercleaningthesurfaceandtwocoatstothereverseofthecanvas(wearadequateprotectionassolventsarerequired).IfyouareusingBEVAfilmitisbettertousetwosheetsoffilmasopposedtoone,althoughonesheetmaybeabletoprovideenoughadhesion.PlacethefilmwiththeBEVA-sidefacingthepanel(orcanvasifyouareusingtwosheets)withoutremovingthesilicone-coatedMylarandapplyheatevenlyusinganiron(BEVAadhesiverequiresatemperatureofaround65.6degreesCelsiustobere-activated).WeightdownthesurfaceuntiltheBEVAhascooledandthencarefullypeelawaythesilicone-coatedMylar(NOTE:IfyouattempttoremovetheMylartoosoonyouwillpulluptheBEVA).Ifyouareusingtwosheets,repeatthisprocesswiththeothersheetofBEVAfilmwhenapplyingtothereverseofthecanvassupport(considerplacingsilicone-releasepaper/Mylarbeneaththecanvaswhenapplyingheat,siliconesidefacingup).ThenpositionyourcanvasdirectlyatoptheBEVAfilm,placesilicone-releasepaper/Mylar(siliconesidefacingdown)atopthecanvas,andapplyheat.IfyouareusingBEVAadhesivesimplywaitforthecoatsofBEVAtodry(inawellventilatedspace)andrepeattheaforementionedstep.IfyouexperiencedifficultiesusingBEVAfilm,tryapplyingacoatofadhesivetothebackofthecanvasorswitchtotheadhesivealtogether.Considerusingatemperaturecontrolledvacuumtableifyouwishtoadhereacompletedpaintingontoapanel.Ingeneralthisisnotrecommendedandheat/pressureshouldbeavoidedentirelyifthepaintfilmisstillfairlyyoung.Itmaybepossibletosafelyadhereyourcompositionifitdoesnotcontainthicklybuiltuppaint,wax-basedadditives,orareasofstrongimpasto.Followtheinstructionsabovebutconsiderusingasoftblotterpaperoveryoursiliconereleasepaper/Mylartoprotectmoredelicatesurfaces(youmayalsoneedtoraisethetemperatureofyourironeversoslightly).

• Provideadditionalauxiliarysupporttolargeformatpanelsandpanels

thatarelessthan¾”thickbyattachingabraceorcradlebygluingstripsofwoodaroundtheoutsideedgeofthebackofthepanelusingthefollowingsteps:

Obtain1”by2”woodenboards(oakormaplearepreferred)andcutthemdowntomatchtheouterdimensionsofthesupport(overallsizewilldependonwhattypeofjoinisusedforthecorners).Buttandmiteredtendtobethemostcommontypeofjoins(considerusinga90degree-cornerclampwhenmakingmiteredcorners),howeverlapjoinsaregenerallyconsideredtobemorestructurallysound.Makesurethatthewoodenboardsareperfectlyalignedandflushwiththeouteredgesbylayingthemonthereverseofthepanelbeforegluingtothereverse(itcanhelpfultomarkthepositionwithapencil).Useanappropriateadhesive(pleaserefertotheDibondManuallocatedinourreferencesection)toadherethewoodenboardsinplacewhiletheglueisdrying,clamp/weighttheboardstoavoidcreatinganyairbubbles.Forlarge-scalesupportsartistsmaychoosetoconstructhorizontaland/orverticalcrossbarsalthoughcrossbarsshouldNOTbeglueddirectlytothereverseofthepanel,onlyfixedtotheouterboardsofthecradleusingglueand/orhardware.

Copper

Artistshaveusedcoppersupportssincethe17thcenturyforbothpracticalandaestheticreasons.Copperpanelsaredurableandcompactandareavailableinarangeofportablesizesbutaremorepronetocorrosionthanaluminum.Acoppersupporttendstogiveawarmtonetotheoverallcompositionasoilpaintsdonotsinkintothegroundastheydooncanvasorwoodenpanelssotheycanremainintenselysaturatedevenwhenappliedinthinlayers.Artistswhochoosetousecoppersupportsshould:

•Preparethesurfacebydegreasingthepresentationsidewithsolvents(e.g.mineralspiritsfollowedbydenaturedalcohol)andcreatingatoothbyrougheningthesurfacewithanabrasivematerial.NOTE:Thereisnoneedtopurchasecostlier“polished”copperetchingplatesasartistsareencouragedtoabradethesurfaceanyhowtoimproveadhesion.

• Sheetsthataretoothinaremorepronetodamageastheycanflexandtwistduringtransportationandhandling.Selectcopperpanelsthatareofanappropriatethickness(e.g.highqualitycopperetchingplates).

•Fix/adherethinnersupportstomorerigidsupportssuchasMasonitebygloballyapplyinganadhesivelikeepoxyinanevenmannertothesheet

and/ortherigidsupport(abradethereverseofthepanelpriortogluingtoimproveadhesion).Ingeneral,however,thingaugecopperpanelsshouldbeavoided.

•Rememberthat“fatoverlean”principlesshouldbefollowedwhenapplyingalkyd,acrylics,and/oroilpaints.

•Avoidaqueous-basedground/paintmaterialsinordertopreventtheformationofcorrosionproducts.

•Notpaintdirectlyonthesurfaceofunprimedcopperasthistechniquemayleadtopotentialadhesionproblemsinthefuture.

OtherMetalSupports

Tin,tin-platediron,steel,zinc,andothermetalshaveoccasionallybeenusedbyartistsassupports.Tin-containingsupportsaresusceptibletocorrosionwhenexposedtohighhumidity,oxygen,andatmosphericpollutants.Zincsupportsarelesspronetocorrosioninhumidenvironmentsthancoppersupports,buttheyaremoresusceptibletodegradationwhenexposedtoacidicoralkalinematerialsandconditions.Athintransparentfilmofzincoxide(whichappearsasabluish-whitefilm)canformonazincpanelwhenitisexposedtoair.Thezincoxidethencanreactwithfattyacidsinoilandalkydpaintstoformzincsoaps(whichmayprotrudethroughthesurfaceasunsightlypustules).Steelandstainlesssteelarenotcommonlyusedassupportsduetotheweightofthesemetalalloys.Steeliscomposedofironandcarbonwithsmalleradditionsofothermetallicelementssuchasmolybdenum,manganese,copper,chromium,ornickel.Thelargerpercentageofchromiuminstainlesssteel(aminimumof10.5%bymass)iswhatgivesitcorrosionresistance.

Slate/Stone/Marble/Porphyry

Itislikelythatvariousstoneshavebeenusedaspaintingsubstratessinceantiquity.Stonesormarblesthathaveafinegrain(arenotporous)andcanbeevenlypolishedarethemostsuitableforuseaspaintingsupports.Stonesupportsaremechanicallystableastheydonotchangewithhumidityfluctuationsandareimpervioustowormsandinsects.Brittleness,poorpreparationofthesurface,andpoorapplicationofthepaintandgroundlayers(e.g.deviatingfromthefatoverleanprinciple)cancausedelamination.Glass

Glasssupportssharethemechanicalstabilityandinsectresistanceofstonesupports,butpossessahighlyfinished,non-poroussurface.However,glassisinherentlyfragileandpronetobreakage(particularlyaroundtheouteredges)andcanbecomemorebrittleasitsages.Aspaintandgroundlayerscanreadilydelaminateduetotheslicksurface,glasssupportsarenotrecommended.Ifartists

choosetouseglasssupports,onlyfrostedorsandblastedglassshouldbeusedandthesurfaceshouldbedegreasedwithethanoloracetonebeforeuse. Polyvinylchloride

Themainissuewiththeuseofpolyvinylchloride-basedplasticsaspaintingsupportsisthepossiblepresenceofplasticizersandotheradditiveswhichmightbeaddedduringthemanufacturingprocess.Withouttesting,itisdifficulttoidentifythespecificpolymerblendspresentwithinapolyvinylchloride(PVC)sheetortoknowhowstablethematerialis.Overtime,anyplasticizersthatmightbepresentinaPVCsheetcanmigratetothesurfaceformingvisibleliquiddropswhichbecometackyandthencrystalline.Thepotentialmigrationofplasticizerscould,inturn,causedelaminationofthepaintand/orgroundlayers.SheetsofPVCcanwarpandwillsometimesgrowmoldwhenexposedtohighlevelsofhumidityandheat.Withoutfurtherstudy,polyvinylchloridecannotberecommendedasapermanentsupportforworksofart.

IftheartistinsistsonusingaPVCsupport,thebestprocedureistopaintonaproperlyprimedcanvasandadherethefinishedcanvastotheplasticsheet.Thisway,iftheplasticsupportdeteriorates,thecanvascanberemovedandadheredtonewsupport. Polycarbonate(e.g.Lexan)

Likepolyvinylchloride-basedplastics,polycarbonatesalsotendtocontainawiderangeofadditivesthatcanposepotentialproblemsforartists.Polycarbonatesarelong-chainlinearpolyestersofcarbonicacidanddihydricphenols(e.g.BisphenolA).Thereareseveralgradesofpolycarbonatesheetingavailabletodayanddistinguishingonefromanotherreallydependsontheadditivespresentwhichcanincludeglassfibers,UVstabilizers,moldreleaseagents,andflameretarders.Thepresence/absenceofthesestabilizerswillinturnaffectthepolycarbonate’sresistancetoheat,itsbrittleness,anditstendencytodegradeinUVlight.Polycarbonatecanalsobeincrediblysensitivetocertainsolvents;artistsshouldavoidbringingacetone,aromatics,andothersolventstosurfaceofPlexiglass,stickinginsteadtowaterormineralspirits-basedproducts.

Theprimaryconcernregardingtheseadditivesistheirtendencytomigrateoutofthesubstrateslowlyovertime(orquicklydependingonthenatureoftheenvironment).Forexample,themigrationofBisphenol-Ainclearpolycarbonateplastics(e.g.waterbottles)hasbeenextensivelystudied,aphenomenonthatcouldverylikelycausedelaminationand/orflakingoftheoverlyingground/paintlayers.Itisforthisreasonthatpolycarbonatesupportsarenotrecommendedforartworksthatareintendedtolast.

PolymethylMethacrylate(e.g.Plexiglas)

Plexiglassisoneofseveraltrademarkednamesusedtomarketclearsheetsofpolymethylmethacrylate,amaterialthatisapopularsupportamongartists.Thesesheetstendnottocontainpotentiallyproblematicadditivessuchasthosefoundinpolyvinylchloride-andpolycarbonate-basedmaterials.However,Plexiglasswillexpandandcontractinresponsetochangesintemperatureandhumidity,leadingtoeventualwarpingorbendingofthesupport.Thiscanbeproblematicifverybrittlematerialsareusedinthepaintand/orgroundlayers(e.g.oils,alkyds,certainresins)asdelaminationandcrackingmayoccurasthesupportexpandsandcontracts.Watercolors,tempera,andmostgouachepaintsshouldbeavoided.Theglassy-likesurfaceofPlexiglassmakesforasurfacethatcanbeeasilyscratchedandcanbuildupastaticchargethatcanattractdustparticles.PlexiglassispronetoyellowingifexposedtoUVlightandcanbeextremelysensitivetocertainsolvents;artistsshouldavoidbringingacetone,aromatics,andothersolventstosurfaceofPlexiglas,stickinginsteadtowaterormineralspirits-basedproducts.Finally,andperhapsmostimportantly,Plexiglasssupportsareinherentlybrittleandeasilyshatterorcrackifdroppedordamaged.

Ifanartistinsistsonusingapolymethylmethacrylatesupport,thebestprocedureistoinitiallysandthesurfaceinordertoprovidesomemechanicaltoothtoimprovetheadhesionofthepaintandgroundlayers.ArtistsshouldconsiderpaintingandprimingwithacrylicsifusingPlexiglassastheydoretainsomedegreeofflexibility.AvoidinstallinginflexiblehardwaredirectlyintothePlexiglass,choosethickerratherthanthinnersheets,anduseachanneledframetohouse/displaythePlexiglass. ADDITIONALREFERENCESANDRESOURCESGeneral“”Supports”inThePainter'sHandbook:RevisedandExpandedbyMarkDavidGottsegen(NewYork:Watson-Guptill,2006).“HistoryandUseofPanelsorOtherRigidSupports”byJorgenWadumandNoelleStreetoninTheConservationofEaselPaintings,eds.Dr.JoyceHillStonerandRebeccaRushfield(LondonandNewYork:Routledge,2012).GoldenArtistColors-PreparingaPaintingSupporthttp://www.goldenpaints.com/technicalinfo_prepsuppGoldenArtistColors–UnderstandWoodSupportsforArt–ABriefHistoryhttp://www.justpaint.org/understanding-wood-supports-for-art-a-brief-history/CAMEO:ConservationandArtMaterialsEncyclopediaOnline(MuseumofFineArtsBoston)http://cameo.mfa.org/wiki/Main_Page

WoodKressTechnicalArtHistoryWebsite-WoodenSupportshttps://www.artcons.udel.edu/about-us/kress/historical-materials-techniques/wooden-supports GoldenArtistsColors-UnderstandingWoodSupportsforArt-ABriefHistorybyElaineSalazarhttp://oldsite.goldenpaints.com/justpaint/jp29article3.php Britannica–WoodSciencehttp://www.britannica.com/science/wood-plant-tissue TransportInformationServices–PropertiesofVariousWoodSpecieshttp://www.tis-gdv.de/tis_e/misc/holzart.htmTheEncyclopediaofWood,U.S.DepartmentofAgriculture,2007[portionsavailable]https://books.google.com/books?id=qxQnAgAAQBAJ&pg=PT354&lpg=PT354&dq=%E2%80%A2+The+Encyclopedia+of+Wood,+USDA&source=bl&ots=MYUmCSV66b&sig=xUESVua9_cPCeLrPxf08t7N_2fQ&hl=en&sa=X&ved=0ahUKEwjard7PxZnOAhUCNSYKHbvzBaMQ6AEIcjAJ#v=onepage&q=%E2%80%A2%20The%20Encyclopedia%20of%20Wood%2C%20USDA&f=false]

Hardboard,Fiberboard,etc.JournaloftheAmericanInstituteforConservation(JAIC)-“Shortcommunicationearlywood-fiberpanels:Masonite,hardboard,andlower-densityboards”byAlexanderW.Katlanhttp://cool.conservation-us.org/jaic/articles/jaic33-03-005.htmlGoldenArtistsColors-PlywoodasaSubstrateforPaintinghttp://oldsite.goldenpaints.com/justpaint/jp29article4.phpAndhttp://www.justpaint.org/plywood-as-a-substrate-for-painting/Ampersand-PaintingPanelsforArtistshttp://www.ampersandart.com/products_main.htmlAmericanHarboatdAssociation-Today’sHardboardhttp://domensino.com/aha/images/tdyhdbrd.pdfCompositePanelAssociationhttp://www.compositepanel.org/CompositePanelAssociation-MDFFromStarttoFinishhttp://www.hardwoods-inc.com/sites/default/files/mdf_start_to_finish_2005.pdf

“Wood-basedCompositesandPanelProducts”byJohnA.YoungquistinForestProductsLaboratory*Madison,WI:I.S.DepartmentofAgriculture,1999)http://www.carbeck.org/pdfs/FPL_Wood_Handbook_Ch10.pdfPanelProcessing,Inc.–“Hardboard(Masonite)Whatisit?”byRMGranumandO.B.Eustishttps://harborsales.net/Portals/0/docs/hardboard_what_is_it.pdfAluminumDibondFabricationManualhttp://graphicdisplayusa.com/downloads/Dibond%20Fabrication%20Manual_May%202011.pdfGraphicDisplay,USA-Dibondhttp://graphicdisplayusa.com/products/dibond/NaturalPigments-ArtefexACMpanelshttp://www.naturalpigments.com/custom-artefex-panel.htmlJackson’s-AluminumPaintingPanelshttps://www.jacksonsart.com/blog/2014/03/28/aluminium-painting-panels/SOSGraphics–SubstrateListhttp://www.sosgraphics.ca/SOSMaterialList.pdfCopperCopperasCanvas:TwoCenturiesofMasterpiecePaintingsonCopper,1575–1775,ed.byMichaelK.Komanecky(Oxford:OxfordUniversityPress,1998).Plastics,etc.GoldenArtistColors–AcrylicsonPlasticshttp://www.justpaint.org/acrylics-on-plasticsSOSGraphicsSubstrateListhttp://www.sosgraphics.ca/SOSMaterialList.pdfPolycarbonatesandotherplasticshttp://www.ptsllc.com/intro/polycarb_intro.aspxPlexiglashttp://www.plexiglas.com/export/sites/plexiglas/.content/medias/downloads/sheet-docs/plexiglas-general-information-and-physical-properties.pdfPlasticsinArt:AStudyfromtheConservationPointofView,byFriederikeWaentig(Petersberg:Imhof.,2008).

PlasticsinArt:History,Technology,Preservation,byTheavanOosten,YvonneShashoua,andFriederikeWaentig(Munich:Siegl,2002).