Vincent van Gogh’s Sunflower in the Van Gogh Museum is at risk of wilting. A new technique shows that the painting’s petals and stems are slowly turning brown as the yellow pigments used are sensitive to light.

Researchers at the University of Antwerp in Belgium and the Technical University of Delft in the Netherlands took two years on analysing the pigments of Van Gogh’s Sunflower at the Van Gogh Museum. By using a new technology called Macroscopic X‐ray Powder Diffraction, without ever touching the painting, they discovered that one of the two chrome yellow pigments used is sensitive to light.

Van Gogh’s Sunflowers in Van Gogh Museum collection

The chrome yellow used in the painting, a synthetic pigment, has a tendency to turn from pale yellow to olive brown colour. Whereas the orange parts of the background to the flowers are more stable and less likely to degrade.

Van Gogh’s Sunflower in Philadelphia Museum of Art collection

The Dutch artist used the chrome yellow pigments in his 'Sunflowers' series and in other paintings. Since the pigment was widely available at the time, besides Van Gogh, many of his contemporaries used several pigments that are sensitive to light. It is possible that many paintings from that era are at risk of discolouration over time.

Van Gogh’s Wheatfield with Crows

It is difficult to say how long will the fading process take for the changes to be obvious. It strongly depends on the external factors like the amount of light.