Van Gogh’s Paintings, Deteriorated By Sunlight
Some of the Dutch master Vincent Van Gogh’s paintings curiously changed their colors, as bright yellow turned to brown. In order to be able to stop the transformation, scientists had to first analyze the phenomena and identify the source of influence. This lead to the use of multiple analytical tools, including an intense X-ray beams produced by the European Synchotron Radiation Facility in Grenoble, France – which is a renowned international center of study for the structure of materials.
According to the results of this study, published in the journal Analytical Chemistry, the paintings must be from now on protected from UV and sunlight, as much as possible.
Although it is known that sunlight can only reach to penetrate a few micrometers into the paint, it was found that, over short distances, it can lead to a misterious chemical reaction that turns chrome yellow into brown pigments, destroying the initial composition. The reaction – new and very complex – was studied using a miscroscopic X-ray beam and was found to cause reactions within an incredibly thin layer of paint, right where it meets the varnish.
Van Gogh’s blending technique of white and yellow seems to be the source that now determins the darkening of the yellows.
Apparently, the darkening of the yellow chrome paint is a consequence of the change of oxidation state between the shades of chromium, going from 6 to 3. After the X-ray beam research, it was proven that chromium 3 is dominant mostly when combined with chemical elements containing barium and sulphur, thus bright yellow mixed with light white.
The vibrating tones in Van Gogh’s work are due to the industrial pigments like chrome yellow, and if it weren’t for those, there would have been no Sunflowers series of paintings, for instance. He was passionate about bright, lively colors and this started to show on canvas only after he left native Holland for France, where he befriended artists with a similar taste.11