By its means the actual painting material on the canvas (or
panel) can be very clearly seen. The raking light examination
is conducted in the following manner. The painting to be
studied is placed vertically on an easel. By moving the easel
into the rays of a strong light, coming from the side (the
angle of incidence of the rays should be carefully noted), the
salient masses in the painting material will stand out in relief
in the raking light--the impastos projecting from the shadows in a very exact manner. Under this light, the painting
can be photographed as many times as required, with slight
variations of angle.
By examining in this manner any well preserved works of the different schools, a great variety of material can observed, according to the medium employed by the artist. Although evidence does not always reveal the difference between a master and his school, it does serve the purpose of exposing fakes and false attributions.
For our further study, there remained the technical treatises on the subject of painting and its processes. Verv few of these gave adequate material to form the basis of practical experiments. One of the most pertinent was the manuscript De Mayerne "Pictoria, sculptia et quae Subalternarum Artium," written in 1620. This author has the great advan- tage of having known Rubens, who, it appears, gave him several notes on his formulas. But de Mayerne is an unsatis- factory writer; he was often too concise to be clear, and in the passages which were of particular interest, the text was thoroughly confusing. A book by Le Sieur Watin on the subject of technique-- "L' Art de Faire et d'Employer le Vernls ou l'Art du Vernisseur," edited in 1772, contained material of more interest, for a house painter than for an artist, and furthermore his formulas covered a period of mediocrity in pictorial technique. The treatises of Bouvier and Paillot de Montabert that appeared in 1830 and 1832 gave the same information as Watin, nothing more. But, J.L.F. Merimee, the father of Prosper and author of "De la Peinture a l'Huile," published in 1830, was more original. He had travelled a great deal and made an intensive study of the old paintings.