And yes, the beautiful and vibrant paintings by Van Gogh are losing their luster ... Blame it on the chrome yellow paint, a bright pigment widely used by Van Gogh, which darkens over time. The phenomenon is known since the mid 19th century, but the chemical process behind this degradation remains poorly understood. An international team has clarified the mystery: the ultraviolet rays cause the loss of electrons chromium ions contained in this particular yellow. Hexavalent chromium (chromium 6) is reduced to tetravalent chromium (chromium 3), which is responsible for the color change. The presence of barium and sulfur appears to strengthen chemical phenomenon for reasons as yet unexplained. But the white paint contains these two elements and Van Gogh was customary for the addition of white in her yellow to make them brighter ... With
This discovery of short-term solutions - protecting film or glass of UV - can be put in place to limit the formation of a dull veil on vivid colors of Van Gogh. Then remains to understand the chemical processes at work trying to develop a method to correct these alterations in hue by chemistry and restore their youthful glow to all tables of the time. When science comes to the aid of art, one can believe ...
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