“A type of bright yellow pigment used by Vincent van Gogh in some of his most famous paintings turns brown in the presence of sunlight, because of a previously unknown chemical reaction, a study has found. Powerful X-ray images of chrome yellow, a toxic industrial pigment used by many artists at the end of the 19th century, revealed that the chromium atoms at the heart of the pigment’s complex chemical structure can be changed in a way that causes the colour to turn from bright yellow to dull brown.

Scientists believe the discovery may explain why some of van Gogh’s most famous works, including his Sunflowers series, no longer appear as they were intended to look when the Dutch post-Impressionist composed them more than 100 years ago, during a period when he deliberately chose bright colours to convey mood and emotion.”