The photographs used to document paintings and works of art are usually made under diffused light conditions. That is, the re-creation by natural or artificial means of those light conditions that render the composition and the various colors the most readable. In other words, these photographs are taken attempting to eliminate any reflections on the surface and at the same time trying to respect as much as possible the normal viewing conditions of the work.
The first step in examining a painting with the intention of obtaining new information and investigating its condition and the artist’s working technique, is to illuminate the work with a band of light raking across the surface.
Raking light means a band of light running parallel to the surface, or at a very narrow angle to the surface. It is necessary that this band be condensed by lenses and be well defined in order to obtain a contrast between the illuminated areas and those remaining in shadow. In addition, it is important to avoid the diffusion of the light because it cancels the effect sought after. Under these light conditions, all the defects on the surface are accentuated to the point that the resulting image of the painting is almost unrecognizable. The raking light makes even the minute flaking of the pictorial film and the ground preparation visible. This information guides the restorer in the execution of localized interventions and in the verification of the results.
An examination under raking light is fundamental for the documentation of the support in relation to its flatness. Canvas supports for example, can slacken with climate variations or with the instability of the stretcher frame. By examining the painting with a band of light parallel to the surface, even the smallest variations and deformations can be seen. In addition, eventual imprints left by the inner edges of the stretcher frame and the cross bar can also be detected.
On wood panels, raking light can easily point out the curvature, distortions and the panel joins. In addition, it is possible to identify deformations in the panel such as bowing, warping, curvature, arching.
This simple investigative technique can provide information that allows us to reconstruct some of the vicissitudes of the object. This can reveal for, example, the almost invisible traces of a support that no longer exists (as in the case of the transfer of a painting from wood panel to canvas); or the flattening out of “impasto” paint areas or thick brushstrokes. In this case the imprints in the paint film left by the original support can be seen.
Raking light can even reveal the presence of a pictorial layer underneath the visible surface. It can point up variations in the flatness of the surface that are not justified by the areas of visible color. In this case, we find ourselves in the presence of pictorial “pentimentos”, or, the reutilization of one painting as the support for a new painting.
Other examinations will be able to establish if this was done by the artist or if we have a fake.
In addition, raking light can facilitate the study of the painter’s technique. This is particularly true when the color is laid on in a thick “impasto”. The raking light highlights the characteristics of the brushstroke: the relief, direction, length, breadth and curvature. By showing aspects of the style and the quality of the pictorial technique, the brushstrokes can be very useful in making attributions, especially if these can be compared with similar images taken from works traditionally considered to be works of that particular artist.
The study of the brushstroke can be even more precise by enlarging the details of the work. A good magnifying glass is useful, but macrophotography is usually the technique that is most used, both because very detailed enlargements can be made as well as allowing for a direct comparison with the brushstrokes on other works.
The observation of the surface under raking light can often help identify the areas that have been re-painted. This type of examination can also be very useful in the observation of the thickness of the pictorial layers. In fact, the weave pattern of the canvas on the surface indicates the presence of a very thin ground preparation.
Manfredi Faldi – Claudio Paolini
Estratto da: Artis (Art and Restoration Techniques Interactive Studio), Direzione scientifica: Manfredi Faldi, Claudio Paolini. Cd Rom realizzato da un gruppo di istituti di restauro europei, con il determinante contributo della Commissione Europea nell’ambito del programma d’azione INFO2000.
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