Why some Georgia O’Keeffe paintings have ‘art acne’
A new imaging technique could help art curators track destructive bumps over time
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Like pubescent children, the oil paintings of Georgia O’Keeffe have been breaking out with “acne” as they age, and now scientists know why.
Tiny blisters, which can cause paint to crack and flake off like dry skin, were first spotted forming on the artist’s paintings years ago. O’Keeffe, a key figure in the development of American modern art, herself had noticed these knobs, which at first were dismissed as sand grains kicked up from the artist’s New Mexico desert home and lodged in the oil paint.
Now researchers have identified the true culprit: metal soaps that result from chemical reactions in the paint. The team has also developed a 3-D image capturing computer program, described February 17 at the annual meeting of the American Association for the Advancement of Science, to help art conservators detect and track these growing “ailments” using only a cell phone or tablet.
O’Keeffe’s works aren’t the first to develop such blisters. Metal soaps, which look a bit like white, microscopic insect eggs, form beneath the surfaces of around 70 percent of all oil paintings, including works by Rembrandt, Francisco de Goya and Vincent van Gogh. “It’s not an unusual phenomenon,” says Marc Walton, a materials scientist at Northwestern University in Evanston, Ill.
Scientists in the late 1990s determined that these soaps form when oil paint’s negatively charged fats, which hold the paint’s colored pigments together, react with positively charged metal ions, such as zinc and lead, in the paint. This reaction creates liquid crystals that slowly aggregate beneath a painting’s surface, causing paint layers on the surface to gradually bulge, tear and eventually flake off.
How these crystals combine is unclear. “I wish we had an answer about why that’s occurring,” Walton says, “but it’s still an open research question.”
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