This is a matter that scientist have been preoccupied with. It looks like the famous painter’s works of art are not exactly in good shape: the color yellow is turning brown and the red is turning white. The cause of it seems to be the pigments used in the paint.
The red painting used by van Gogh is the red lead pigment. Ever since ancient times artist have used this shade and considered it brilliant, but over time, the ageing process causes the color to fade.
Koen Janssens of the University of Antwerp together with a team has studied the process of degradation of red lead. They examined a sample from Vincent van Gogh’s “Wheat Stack under a Cloudy Sky” using PETRA III, a storage-ring-based X-ray radiation source in Germany. This alternative was far better than the traditional X-ray crystallographic one because there was no need to cut the sample open. The technique used was x-ray powder diffraction tomography. With this method they obtained detailed information about the composition of the sample. The researchers determined the dispersion of various crystalline compounds.
They discovered that the color was still intense at the center of the sample. The color closer to the surface changed and it protected the original pigment. It was quite surprising for the investigators to find out this since red lead was considered to be very stable in the art world.
The outside layer of the pigment was made out of plumbonacrite, carbonates, cerssites and hydrocerussites. The conversion into plumbonacrite was caused by the sun light and in reaction with the carbon dioxide, the plumbonacrite formed white crystals. In addition, the degradation might have also been caused by existence of impurities in the red lead pigment. What made the condition of the painting worse was the fact that during restoration processes white pigments of zinc were added in an attempt to highlight the white pigments in the pond.
The findings of this study will be of use in the future, when experts will try to restore the original hue of the colors in van Gogh’s paintings. However the results are alarming because they show that many of Van Gogh’s paintings are threatened. Not only science, but museums too can play an important role in slowing down the process of degradation: the environment in which the paintings are kept could be changed and the same goes for the amount of light inside the museums.
Image Source: Science Daily