Why van Gogh's Sunflowers are wilting

The colour of Vincent van Gogh's famous Sunflowers is changing over time, because of the mixture of pigments used by the Dutch master in his painting. Evidence for the process now comes from a detailed spectroscopic investigation of the Sunflowers version at the Van Gogh Museum in Amsterdam. A group of scientists headed by Letizia Monico from the Institute of Molecular Science and Technology (CNR-ISTM) of Perugia, the University of Perugia and the University of Antwerp, shone X-rays from DESY's