“Bank of the Seine,” pictured above, is one of the two paintings by Vincent van Gogh studied. Credit: Vincent van Gogh Museum, Amsterdam.
Despite restoration efforts, some paintings may appear less brilliant then they did when they were originally crafted.
In the case of one 19th-century artist’s work, scientists are using high-tech tools to pinpoint the cause of an undesirable chemical change in paint color.
Synchrotron X-ray technology, which allows a powerful and up-close look at the molecular composition of surfaces, has previously been used to look underneath layers in paintings — their skeletons, so to speak.
Now a team of researchers has found a new use for these tools to study a chemical reaction of chrome yellow, also called lead chromate, that degrades vibrant yellows to dark browns. The findings help curators and restoration specialists protect other paintings composed with the chemical.
The collaborative study, published in the peer-reviewed journal Analytical Chemistry this week, confirmed chemical changes in chrome yellow in two of Vincent van Gogh’s paintings. Although his Sunflower pieces weren’t studied, they demonstrate why this color makes van Gogh’s work stand out. The scientists validated previous hunches that UV light and sunlight are to blame for catalyzing chemical reactions of chrome yellow on canvas.
What’s especially interesting is the way the scientists came to their conclusions. They studied the chemical properties of chrome yellow paint left in historic tubes from this time period. After noticing the darkening of chrome yellow when exposed to a UV lamp for several hours, the group used X-ray technology to confirm that the source of the darkening stemmed from chromium(VI) changing to chromium(III) in the paint.
The research also showed that varnishes aren’t entirely protective in art preservation. In fact, the chrome yellow chemical reaction occurred between the layers of varnish and paint.
So how often do paintings receive such attention?
Not too often, especially since these analyses often require transporting delicate pieces of artwork to labs in different countries. That said, using chemistry and new technology is particularly useful because researchers can look at several layers of a painting without removing them.
Who said science and the humanities can’t get along?