painted under a layer of old varnish signatures and inscriptions can sometimes be detected by infrared rays. It must, however, to stress once again that the identification of the old signature, even under the account or under the other signature is not necessarily indicative of its authenticity. Intentional slight brushing false signature - a well-known method counterfeiters, calculated that the signature will be "accidentally" found during the washing of painting and confirm the "authenticity" paintings.
An important point in the process of studying the paint layer is to determine its safety. What is it explorer - with the author's paintings or her likeness recreated hand restorer, which plots painting survived intact, and which are rewritten? Needless to say, how important it is to get the correct answer to such questions in the course of, for example, the attribution of the painting.
Determination of safety of the paint layer would be best to start with his views in light of the visible luminescence, excited by ultraviolet radiation. If the picture in the light of luminescence emitted uniform milky-blue light, in which the image appears as a disguised transparent cigarette paper, one can conclude that the painting is well preserved. Some dark spots on the background luminescence lacquer surface may indicate worn or partial loss of lacquer on the small retouch on stony ground and breaking the paint layer. Lots of paint layer subjected to restoration records and toning lacquer surface, clearly visible in the light of luminescence by visual inspection pictures and photos in the form of dark spots showing the location and size of records. We can distinguish toning and under a layer of varnish: if the latter is not very thick and not too decomposed, such toning look much paler than that made by polish ..
http://www.art-con.ru/node/288
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But expert opinion-Petrova V. (signature on dry, or over the varnish).
Technology, as a blood test, only an aid to the diagnostician. Technological scheme - canvas, the nature of the soil, drawing, color, general methods of constructing the paint layer is very similar for many artists, especially - academics XIX century that the German, that the Danish, that Russian. Radiograph is not always without a range of other studies, may give the correct result. For paintings Levitan, for example, is characterized by several types of X-rays.
As the signature - that's at least a Surikova almost any signature "hanging" on the varnish. So if you rely on it, all our Surikov have a museum pass. But some artists - such as Kuindzhi and Vasily Vereshchagin - almost all are signed, and signature on any sketch not so much convincing as alarming .
http://www.wm-painting.ru/Novosti_mi..._articleid/111