Scientists have identified why the bright yellows in some of Vincent van Gogh's paintings have turned brown.

A complex chemical reaction is behind the deterioration of the works.

The finding is a first step to understanding how to stop some of the Dutch master's most famous paintings from fading over time.

The results, published in the journal Analytical Chemistry, suggest shielding the affected paintings as much as possible from UV and sunlight.

Uncovering the secrets of the chemical reaction required the scientists to use an array of analytical tools....