Berwyn Lapesey blog

X-rays reveal why Van Gogh's yellows turn brown

WASHINGTON (AFP) – International scientists have discovered a chemical reaction that has caused the once-vivid yellows in Vincent van Gogh's paintings to turn brown, according to a study published in the United States.

A super-sensitive microscopic X-ray has revealed a chemical reaction taking place where the paint meets the varnish, triggered by sunlight which causes yellow to fade, said the findings published Monday in the journal Analytical Chemistry.

"This type of cutting edge research is crucial to advance our understanding of how paintings age and should be conserved for future generations," said Ella Hendriks of the Van Gogh Museum Amsterdam.

The X-ray from the European Synchrotron Radiation Facility in Grenoble, France also showed a reduction in chromium "was especially prominent in the presence of chemical compounds which contained barium and sulphur."

That observation led scientists to believe that "Van Gogh's technique of blending white and yellow paint might be the cause of the darkening of his yellow paint," the study said.

The best way to avoid such deterioration is to shield vulnerable artwork from ultraviolet rays and sunlight, the study authors said.

"Our X-ray beam is 100 times thinner than a human hair, and it reveals subtle chemical processes over equally minuscule areas," said Marine Cotte, a scientist with the research institute in Grenoble.

"Making this possible has opened the door to a whole new world of discovery for art historians and conservators."

The research was led by Koen Janssens of Antwerp University in Belgium. Letizia Monico, an Italian chemist, headed the experiments. Scientists from Italy, France and the Netherlands were also part of the team.

Van Gogh, known for his bold, tempestuous brushwork and having cut off his own ear, died at Auvers-sur-Oise near Paris in July 1890 after shooting himself in the chest.