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CHEMICAL ANO PHYSICAL TECHNIQUES FOR THE CONSERVATION OF STONE MATERIALS: INTERDISCIPLINARY APPROACH AND SPECIFIC NATURE OF THE DISCIPLINE.

D'AVINO, STEFANO DSSAR, Universita di Chieti

Methodological premises "In restoration, the preeminent aspects are the operations of a strictly conservative

nature, aimed at preserving from decay the materials that contribute to the physical constitution of the work. In this sense, the restoration of monuments is to be viewed as a discipline based on a critical, historical foundation, substantiated by the contributions of the physical and natural sciences." This definition of the discipline of restoration, or more precisely, the activities related to conservation, expressed about twenty years ago by Giovanni Carbonara, 1 takes us to the very heart of the view previously sustained by C. Brandi2: "we only restore the material of the work of art". The restoration aims primarily at perpetuating the ancient material, that which is (held to be) original and that which has been created by the passage of time, that has contributed an added value to the original monument, eluding every renovation that would nullify the continuity of the historical process. The practice of conservation is thus both "critical-historical judgment", which is also reflected in the choice of the most suitable methods and conservation techniques, and "scientific-technical knowledge", which is the direct result of laboratory analysis.

If, on the one hand, restoration must by its nature involve the transformation of the material - albeit a transformation well defined "in a precise and binding sense" and in accordance with a rigorous critical process - on the other, from a strictly technical point of view, the conservation of an object whose value is as a simple document of a time, or that is considered an artistic, or otherwise unique or irreplaceable expression, is none other than an attempt to retard the inevitable evolutive processes that have been "provoked by the lack of equilibrium between the object and the environment that surrounds it". Consequently, "the first step in the activity of conservation cannot be other than diagnostic, the recognition of the chief identifying values of the monument (viewed as "object" and as well as "reason" for the transmission to the future of the monuments, in which they are embodied). The more precise the information about the current state of the monument and the cause of the damage, the greater the chances are of succeeding in the attempt, which we call conservation, to delay the

alterative processes".3

The central nucleus around which the debate revolves, and which forms the object of the efforts of conservators to develop the technique, is the material: material interpreted as the indissoluble support to the form: Material that testifies to history, "as the interweaving of relationships that are knowable only in part, that can be recaptured only in part ... conservable only in part, but that nonetheless represents large part of our cognitive experience".

4 The

knowledge of the material reality of the monument thus also transforms the conservation effort into an historical and "authentic" event, and the decay of the stone into uneliminable signs of the passing of time, of the loss and at the same time the growth of values. Thus, there is no "separation among formal, or esthetic, authenticity, material authenticity and historic

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authenticity".5 They all form, together, "an organic concept, embodied in works that are always,

at one and the same time, material and form".6

The progress made in · the field of instrumentation for analysis and applied research

today allow us to target the conservation of the material that constitutes the work and thus the

conservation of its authenticity. The potential offered by technical-scientific experimentation has enabled the conservation-related aspects of restoration to assume an operative importance

unknown until just a few decades ago, before which time unfettered experimentation reigned. Such an approach, given the high level of specialization rmplied therein, inevitably

leads to a revision of the techniques of intervention on the monuments that allows for a multi­

disciplinary approach, a need that was very strongly felt among restorers:7 "It is a matter of harmonising, starting right from the design of the methodology itself, the different knowledge

processes that characterise the various disciplines called upon to cooperate; ... knowledge here signifying (above all] the means of identifying the operative choices"8 that will inevitably influence the future cognitive approach. These operative choices (though identifiable through the contributions from the physical and chemical sciences) must nevertheless not impose conditions upon the restoration intervention, diminishing it, transforming it into an evaluative critical judgement or the first moment of the knowledge of the work.

Over the last several decades, the restoration intervention had undergone "a significant evolution. (from the use of] traditional technologies of a pseudo-artisan nature (executed more on the basis of experience than analysis), the field has moved to the application of diagnostic and intervention technologies", especially with regards to the knowledge of the materials, "of a more advanced nature, that required an inter-disciplinary approach".9 Consequently, there is great encouragement of all those types of research that concentrate on the characteristics of the materials and on the alterative, physical and chemical phenomena. and that can provide a contribution to progress in the field of conservation. Such results are achievable only through the application of analytical techniques, the taking of measurements with sophisticated instrumentation, and a scientific knowledge of the fields of physics, chemistry, biology and mineralogy.

Running parallel to the study of the compatibility between the so-called traditional materials and "restoration" materials is the development of "detailed scientific research on ancient materials and their behavior", encouraging, through inter-disciplinary studies, a constant honing of the techniques in order to ensure that conservation practice is oriented "toward less improvised interventions"10

, overcoming that "lingering "purovisibilistic" view [that puts the accent on values that are purely esthetic and thus visible)"11 that sometimes prohibits the conservator from taking a strictly scientific position with regards to the material of the monument.12

The identification of the operative choices, precisely because it requires advance decision-making, should therefore be taken as the first planning input, as the critical option that must by necessity be founded upon a profound and thorough understanding of the work.

Analytical results and the multi-disciplinary approach

Despite the increasingly evident joint research in the field of conservation and the consequent need for an inter-disciplinary approach, the "individual sciences", observes Brandi, 1

3 continue to "develop independently of one another, each with its own formalized

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language, so specific to each individual field", thereby greatly reducing the possibilities both for a critical comparison and a control of the results, and in effect requiring acceptance of the conclusions of a science that "we want to exploit in a different field".

This observation leads us to a reflection, expressed by Bertrand Russell, on the barrier that exists between the impressive scientific and technological advances, on the one hand, frequently generated for profit, and the research "freedom" (we would add "disinterested" freedom) that scientists might boast of, on the other, but which all too often - with regards to conservation-as-science - leads to the creation of excessively diverse methodologies and a failure to create a rigorous, unified lexicon. The outcome in essence is the lack of interaction between the applied methodology and the laboratory results, when in fact "the same practice can constantly present new challenges to the theory, just as technique promotes broadened scientific horizons. "14

In addition to the essential "disciplinary alienation" that can occur in the practice of conservation, it is important to note the conceptual limits imposed by the in corpore viii application of the results of research conducted in the laboratory. "The unforeseen opportunity to conserve the authentic materials of works of the past should have revolutionized principles, theories, purposes and operativity in the field of protection of monuments. ( ... ) A true revolution should have developed a proper, unified theory of restoration, while the fragmented research for the conservation of the authenticity of the materials goes forward ... without a precise guiding orientation."15 In fact, the heterogeneity and variability of the physical parameters found in the monuments object of the intervention, as well as their peculiarly unique character and the formal-historic value of each (which essentially means that the events and objects of the restoration are absolutely unrepeatable), make it impossible to base the operativity on rigorous scientific bases that might receive a sufficient degree of corroboration.

It is therefore fundamental not to transfer, in a generalized manner, the results of scientific research conducted in the laboratory to actual application, because the positivistic exaltation of the "material culture" could erroneously lead to the conclusion that the contribution of history is unessential, and that it is proper to presume full autonomy of the technical­conservative operation, to such a degree that "it is identified with the restoration itself'; with the result that "favoring of the technical-material input would aggravate the historical-technical dichotomy" .16 On the contrary, the "material" history of the monument, documentation of which also includes thorough research of the files, provides a precious insight to understanding the alteration processes as well as useful indications for "a fine-tuning of treatment methods and

materials".17

The dialectic link between document and decay mechanisms, between "observation" and laboratory results (which can sometimes lead to the identification of reference materials and processes) favors the process of corroboration of the data, substantiating the operative

choices. Nonetheless, the discipline of conservation cannot be reduced to a manualistic

approach, to a set of "rules" that can be used to guide every and any operation: to the Kantian nexus between the world of ideas (theory) and the phenomenological world (reality), must be juxtaposed the supremacy of knowledge, intended as the critical interpretative moment in which the project establishes its "relationship, complex and irregular, with the object to be restored".18 It is, however, possible to define a relationship, an operative dependency, between

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historical knowledge and techno-scientific skills, in particular in the reading of the mechanisms of decay, in a "continuous fusion" of historiographic and physical-chemical contributions: ''the deterioration, a ceaseless process, should be considered", according to Paolo Fancelli, "from an historical point of view, in complete harmony with the investigation being conducted on the

monument" .19

Research and the conservation project We agree with the hypothesis according to which the technical and scientific

methodologies must be viewed in relation to the historical-critical and theoretical challenges posed by the restoration; they cannot be considered extraneous or juxtaposed to, or, much less, independent from, these challenges, because the result of the investigations inevitably influences the intervention procedures.

The "culturally aware" technical effort, reflecting a perspective that reflects an understanding of, and commitment to, the "entire history of the restoration", must be subjected to the verification of the more general critical reflection and the cultural orientations that are guiding the act of restoration".20

The validity of the assertion, irrespective of any rigidly technicistic anti-historical position, is in the recognition that scientific results have the essentially modern capacity to safeguard the figurative physical value of the monument, thereby precluding any attempt at substitution.

Absolute respect for the material, therefore, imposes, together with the criterion of minimum intervention, the search for compatibility between the materials utilized in the restoration and the "historical" materials, as well as their "reversibility" and "distinguishability". This objective can be achieved only through a thorough knowledge of new applicative technologies and a comprehension of the analytical results: the decision-making process that leads to the choice of intervention options thus becomes collegial. The plethora of types of data necessary and the interpretation of such data must in fact be viewed as the fruit of specific skills, "distinct disciplinary contributions that must nevertheless be evaluated in the context of the specific project". 21

1 G. CARBONARA, Storia, scienza e tecnica def restauro, in "Antiqua", IX, Sept.-Dec. 1984, 5-6, p.

20. 2 Cf. C. BRANDI, Teoria def restauro, Roma, 1963. 3

M . LAURENZI TABASSO, La conservazione dei materiali lapidei: aspetti scientiflci e tecnici , in "Bollettino d'arte", supp. 41, vol I, 1987, p. 1. 4

Cf. A. BELLINI, II progetto di conservazione come forma di conoscenza, Minutes of the convention on: Restauro: la ricerca progettua/e, (Bressanone 1989), Padova 1989, p. 576. 5

G. CARBONARA, Presentation to the International Study Day onAutenticita e patrimonio monumentale (Napoli October 29, 1994), in "Restauro", XXIII, n. 130, Oct-Dec. 1994, p. 33. 6

"The idea of "formal authenticity" is based on a synchronic cut that forcefully rends the continuity of the historic process" compared with a concept of authenticity that progresses diachronically with history. 7

A. A VET A, Scienza e restauro in "Restauro", XV, n. 86, July-Aug. 1986, p. 86. 8

R. FR.ANCl-Il, L. MARINO, G. VANNINI, II cantiere di restauro come area interdisciplinare,. Minutes of the meeting on Restauro: la ricerca progettuale, (Bressanone 1989), Padova 1989, p. 85.

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The problem with of the search for a "basic affinity in the research methods in order to render the analytic results homogenically comparable" was more recently emphasized by Paolo Fancelli (cf. P. FANCELLI, II restauro, oggi, tra ripristino e conservazione scientifica" in "I saggi di Opus", 3, 1995, p. 30). 9 E. BISCONTIN, Problemi di compatibilita tra vecchi e nuovi materia/i. Orientamenti relativi a/l'utilizzo e sperimentazione dei materiali nel restauro, in "Restauro e Citta", I, n. l , p. 33 10 G. CARBONARA,Storia, scienza e tecnica ... cit., p. 17. 11 P. FANCELLI, Conservazione e scienze chimico-fisiche, in "Storia Architettura", XI, n. 1-2, 1988, p. 56. 12 This point is also among the admonitions of an art critic and historian such as Cesare Brandi, clearly not an exponent of exaggeratedly technicistic positions: "It is the material and not the work of art that must be analyzed scientifically: in otl1er words, the object." (cf. C. BRANDI, Report to the International Congress of the Academy of the Lincei on Applicazione dei metodi nucleari nel cam po de/le opere d'arte, (Roma-Venezia, May 24-29, 1973, Roma 1978, inf/ restauro. Teoria e pratica., by M. CORDARO, Roma 1996, p. 46) 13 C. BRANDI, op. cit., p. 43 14 P. F ANCELL!, Conservazione e scienze ... cit. , p. 56. 15 P. FANCELLI, JI restauro, oggi .. . cit., p. 21. 16 G. CARBONARA, Storia, scienza e tecnica. .. cit., p. 20. 17 M. LAURENZI TABASSO, op. cit., p. 8. 18 E. VASSALLO, JI primato de/la conoscenza, Minutes of the Convention, Bressanone 1988, p. 354. 19 P. FANCELLI, Conservazione e scienze ... cit., p. 60. 20 G. CARBONARA, Storia, scienza e tecnica ... cit., p. 19. 21 S. FILIPPI, L'intervento sul costruito: attivita interdisciplinare o pluridisciplinare?, Minutes of the Convention on Restauro: la ricerca progettua/e (Bressanone 1989), Padova 1989, p. 639.