Artistic diagnostics includes a set of procedures and techniques aimed at discovering and studying the creative path and the material of which a work is composed. It is now commonplace to mention how a restoration intervention on a work of art must be preceded by a collection, as large as possible, of historical information and scientific analyzes aimed at a thorough knowledge of the object, in order to correctly structure its restoration operation.
Artistic diagnostics cannot and must not be an end in itself, but must represent the collection of a set of data obtained with the application of the various methods of analysis, the processing of which must form the basis for collaboration between experts in the technical, scientific and historical sectors who, through a broad and complete evaluation of said data, will be able to draw the most correct conclusions.
The information obtainable through diagnostic methodologies is not easy to interpret if the principles on which they are based are not well known. At the same time it is extremely useful that the execution of the examinations is carried out, as much as possible, by the restorer himself: as he proceeds in the material execution of the intervention, he will be able to re-elaborate and correctly interpret what the investigations have shown him, he will be able to accurately assess when and in which areas to perform the tests again and take samples to be subjected to the chemical investigation in the laboratory.
Manfredi Faldi, Claudio Paolini, Tecniche fotografiche per la documentazione delle opere d’arte, Quaderni dell’Istituto per l’Arte e il Restauro, Florence 1987
- Visible light
- UV fluorescence
- Transmitted light
- Raking light
- Infrared colored photo
- IR transirradiation
More and more refined and precise tools are available to the art historian and restorer even if, even today, the investigations that make the most interesting contributions to restoration, conservation and historical-stylistic investigation remain the X-ray radiography, the cross-sections and the infrared reflectography as well as the simple raking light examination. These analyzes debunk, as many experts have repeatedly reiterated, the nonsense of the “combination of cognitive investigation and sophisticated technology” . This means, as Claudio Paolini states, “that an investigation technique will provide clear results that meet the various needs only if correctly chosen in relation to the nature of the object to be investigated and not based on its complexity” , simple, less spectacular and less expensive methods can achieve surprising and irreplaceable results in the field of material interpretation of the work.
As mentioned, the scientific examination cannot and must not be an end in itself, but must represent the collection of data obtained through the analizes deemed necessary and the processing of this data should involve experts in different sectors. The most correct conclusions can be drawn from such a collaboration .
Integration with the historical-stylistic analysis
Th collaboration between science and art is affirming itself year after year; not too long ago the art historian had no scientific expertise and could request laboratory analyzes only occasionally, even so, most of the times he did not have sufficient preparation to be able to draw a correct reading from them. On the other hand, the scientist also examined the artistic object and carried out its analysis with the “ease” and “coldness of a laboratory datum”, without perceiving it in its historical and cultural “vitality” .
Knowing the tools, as Stefano Colonna briefly underlines, above all means knowing how to “evaluate the potential in relation to the purposes to be pursued, in order to use the tools correctly in any study of applications that are still mostly unpredictable and require specialistic scientifically correct preparation” .
It is essential to know which exams are currently available in order to orient oneself in the preliminary choice of these and possibly be able to integrate them without improper use; at the same time knowing how to draw from them the greatest possible number of useful information for what concerns both the examination of the pictorial material and the study of the creative path.
While approaching a brief description of the individual diagnostic methods currently used in the field of conservation and restoration of works of art – more particularly of pictorial works – we must not underestimate the importance of a careful visual analysis which, if conducted by expert eyes and in the preliminary phase of each examination, can help us avoid gross errors of evaluation and limit the number of investigations to which the work is subjected.
It is clear that the visual examination makes use of various tools some of which are commonly used such as the magnifying glass or the low magnification binocular microscope, while other means are the prerogative of the restorer and can be used only at the time of restoration, such as the scalpel or the use of solvents for carrying out tests on small areas of the work.
On the other hand, the decision to carry out scientific investigations on an art object coincides more and more with the need to carry out its restoration and therefore the figure of the restorer joins that of the art historian and scientist as technical expert in the examination of the pictorial material and, in particular, of the state of conservation of the painting, making a precious and irreplaceable contribution.
Photographic recordings are often used even when the examination we are carrying out is directly observable with the naked eye, but in addition to the importance of permanent documentation, there are other reasons that make photographic recording necessary: through photography conducting a joint study of the various exams by comparing the images obtained is possible; the photographic film then has the property of accumulating light by extending the duration of the exposure, thus making it possible to record details at very low brightness; finally, by choosing filters, films and high-contrast developments, the interpretation of these investigations can be facilitated.
In the preliminary phase of the intervention, the restorer will try to establish the state of conservation of the artifact, how much of what is visible on the painting is original and how much was added later. We know that in the past respect for the authenticity of the work was a relative concept while it was stronger “the effect exerted by the work intact” . The restoration often, therefore, had no other purpose than to compensate for the damage  and large areas of paint were covered by new layers of color only because they were close to areas that presented deficiencies to be completed.
Overpaintings and pictorial retouching
An initial evaluation is always possible by the restorer or art historian even without resorting to special techniques, as the repainting and pictorial retouching often differ from the original for the chromatic alterations to which they are often subject and for the imperfect physical conformability with the surface of the work. However, cases in which even the most expert eye is unable to correctly evaluate the extent of the restorations is not rare, therefore he or she seeks lighting conditions that can accentuate the differences in the surface trend, for example by moving the light source so as to have a perfect specular reflection of the affected area, or illuminate the work so that the light strikes almost parallel to the pictorial surface.
Often the effect obtained in “raking light” or “tangential” light examinations is clearly superior to any expectation, especially if a direct light source, well directed with condensers and hoods, is used to accentuate the contrast of the shadows that the small reliefs of the surface produce and it is therefore from this simple examination that the study of the work of art usually begins.
Manfredi Faldi, La documentazione materiale come supporto e verifica dell’analisi storico-stilistica nelle opere pittoriche, Florence 2003 pp. 13-16
Cfr. AA.VV. , Le indagini conoscitive e il restauro: alcune considerazioni, in “Kermes”, II, n. 6, settembre-dicembre 1989, Firenze, Nardini, , p. 8.
Cfr. M. Faldi, C. Paolini, cit., 1987, p. 11.
Cfr.S. Augusti, cit., 1963
Cfr. S. Colonna, ‘BTA – Bollettino Telematico dell’Arte”, 10 febbraio 2001, n. 249.
C. Chirici, Il problema del restauro, Milano, Ceschina 1971, p. 1
Cfr., M. Cagiano De Azevedo, Il gusto nel restauro delle opere d’arte antiche, Roma 1948.