Lead chromate

Lead chromate is a well-known colouring agent, or pigment. We find it in the yellow colour of many old paintings. Painters have used many different pigments over the centuries. It is one way that helps us to identify forgeries.

Vincent van Gogh used this toxic pigment in his paintings, mainly because it was cheaper than other yellow pigments. Lead chromate is a powder made from crocoite, a yellow-orange mineral.

Over time the chemical composition of lead chromate changes through exposure to oxygen, gradually changing the colours in paintings from yellow to brown. No remedy has yet been found for this problem, which adds to the difficulty of restoring paintings.