JOIN USChemical reaction behind Van Gogh paintings deterioration
The scientists in Europe, involved in the research, say that the finding is the first step to understanding how to prevent the bright yellows in some of the Dutch master’s most famous paintings from turning brown.
The results, published in the Analytical Chemistry journal, suggest shielding the affected paintings as much as possible from ultra-violet and sunlight.
The scientists required an array of analytical tools to uncover the secrets of the chemical reaction, including the intense X-ray beams produced at the European Synchrotron Radiation Facility (ESRF), a world’s leading centre for the study of the structure of materials in Grenoble, France.
Sunlight can penetrate only a few micrometres into the paint, but over this short distance, the researchers found it could trigger a hitherto unknown chemical reaction turning chrome yellow into brown pigments, altering the original composition, the BBC reported. The scientists employed a microscopic X-ray beam to reveal a complex chemical reaction taking place in the incredibly thin layer where the paint meets the varnish.
The vibrancy of new industrial pigments such as chrome yellow allowed van Gogh to achieve the intensity of, for example, his series of Sunflowers paintings. He started to paint in these bright colours after leaving his native Holland for France where he became friends with artists who shared his new ideas about the use of colours.
The scientists found that a change in the oxidation state of the element chromium (from chromium 6 to chromium 3) was linked to the darkening of chrome yellow paint.
The X-ray beam research carried out at ESRF also showed chromium 3 was especially prominent in the presence of chemical compounds which contained barium and sulphur.
Based on this observation, the scientists speculate that van Gogh’s technique of blending white and yellow paint might be the cause of the darkening of his yellow paint.