We begin our objective study of authenticity by establishing the same line of inquiry that a museum does when receiving a new acquisition. Examination into the authenticity of a painting generally follows the sequence employed in determining treatment of a damaged or deteriorated painting.
The first step is to look at the painting. The use of the human eye is the most effective examination method (Color Plate 22). Visual examination by an art historian, curator, or conservator who is familiar with the production of the artist to whom a work is attributed is the first in a series of technical steps in laboratory analysis. It is in the first glance at a painting that one's visual encounter may stir doubts about authenticity.
Photography in normal, infrared (IR), and ultraviolet light is the next stage in the process. Photographs of the front of the painting under normal illuminations are accompanied by photographs using raking or tangental illumination to bring surface irregularities into bold relief.
Infrared reflectography (Chapter 7) allows a view beneath the surface. Underdrawings contrasting with a white ground show up in the IR and through their correlation with subsequent layers of painted images may indicate how images evolve as the painter considers issues of iconography, description, and composition. These layers are in varying degrees transparent to IR. In the same vein, x-radiography allows a view beneath the surface. With this proceedure one does not rely on the transparency of paint to infrared radiation, but instead utilizes the increased absorption of x-rays by pigments containing high-atomic-number elements such as lead white or mercury, which is present in the color vermilion. The x-radiograph of Color Plate 23 given in Figure 8.2 shows the white areas in the face and in the book due to the presence of white lead. X-radiographs are used to reveal revisions (pentimenti) in the painting and the structure of the support on which the ground and subsequent layers have been applied.
In the search for fakes, infrared reflectography and x-radiography play an important role. Because under-drawings and revisions are quite common in authentic paintings, their absence might suggest chicanery. The lack of underdrawings or pentmenti alone, however, is not proof of fakery.
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