Normally, cadmium yellow grows paler and less vibrant as it ages.

BBC: Van Gogh's Flowers In A Blue Vase damage seen in X-rays

The new work was begun during a conservation treatment in 2009, when conservators found that the yellows in Flowers In A Blue Vase - this time from a pigment called cadmium yellow - had turned greyish and cracked.

BBC: Van Gogh's Flowers In A Blue Vase damage seen in X-rays