Van Gogh Varnish Discoloration

Using sophisticated x-ray beams at two synchrotron sources in Europe, scientists have identified a previously unknown degradation process between paint and protective varnish in Van Gogh's painting, Flowers in a blue vase, a reaction between the cadmium sulphide in the paint and lead ions in the varnish to form an opaque anglesite (PbSO₄) and cadmium oxalate (CdC₂O₄).