Scientists had noticed an odd color change occurring in Vincent Van Gogh's "Flowers in a blue vase," which he painted in Paris in 1887. Apparently, the yellows were turning orange-gray over time (see the discoloration in the upper right). Researchers reporting in the journal Analytical Chemistry have found a chemical reaction at the interface of a protective varnish and the paint is the culprit. The boxes show where tiny paint samples were taken for analysis.
The color-change (from bright yellow to orange-gray) in Van Gogh's "Flowers in a blue vase" can be seen to the right and upper right of the painting. Two microsamples were taken from these areas.
From the tiny paint sample (shown in an optical-microscope image), the researchers looked at levels of four compounds.
Microsamples from art masterpieces, molded in Plexiglass plates ready for investigation with synchrotron X-rays. The historic paint tube at the bottom is from the personal collection of M. Cotte.
Artist's illustration of a Plexiglass plate with a microsample mounted for investigation in the vacuum chamber of the synchrotron X-ray microscope. The small spot in the center of the Plexiglass block is the sample from the Van Gogh painting, and the cylindrical tube connects it with the X-ray detector.
Researchers have also analyzed Van Gogh's "Banks of the Seine" (1887), finding a chemical reaction caused the painting to lose its luster.