The color red is also posing a problem in works like Wheat Stack Under a Cloudy Sky, and researchers are now moving closer to finding out why, Chemistry Worldreports.
Van Gogh often used a pigment known as red lead. The stuff, also called minium, turns whiter when it’s exposed to light. Seeking to understand the process, researchers analyzed a tiny dot of paint from the work.
The process, which involved shooting X-rays at the paint, showed that the red lead is now covered with what Chemistry World calls “degradation products” in the form of other chemicals.
The researchers found a substance they call the “missing link” in the degradation process: It’s a mineral lead known as plumbonacrite, Hyperallergic reports. Light shining on the plumbonacrite has apparently caused the buildup of other chemicals.
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