Quirks & Quarks

Art gets a bad case of acne and it has conservators concerned

Oil paintings around the world are developing thousands of tiny protrusions that have conservators concerned

Oil paintings around the world are developing thousands of tiny protrusions

This painting has "art acne" on its surface. This is Georgia O'Keeffe's 1941 painting, Padernal. (Dale Kronkright / © Georgia O'Keeffe Museum)

Something strange is happening with oil paintings around the world.

They're developing thousands of tiny pin-sized protrusions, like pimples on the surface. And the growth has been seen to to spread in the paintings, causing concerns among art conservators about possible damage to the art.

In a new study, researchers from Northwestern University, in collaboration with the Georgia O'Keeffe Museum in Santa Fe, New Mexico, have figured out the cause of this "art acne." They've also created an iPad-based imaging tool to help monitor and diagnose the health of oil paintings.

Art gets a bad case of acne

For decades, conservators thought "art acne" was only a problem in older paintings. But a few years ago, conservators spotted them on a modern Georgia O'Keeffe painting.

Georgia O'Keeffe is the famous 20th century abstractionist American artist, best known for her paintings of flowers and abstract landscapes. The protrusions were originally thought to be grains of sand trapped in the paint, but they have now been diagnosed as something produced by a the interaction of materials in the canvas and paint: metal soaps.

A close-up of one of Georgia O’Keeffe’s paintings showing the signs of ‘art acne. (Dale Kronkright / Georgia O’Keeffe Museum)

They're the result of a chemical reaction between metal ions such as zinc and lead in the paint, and fatty acids commonly used as paint binders. They form crystalline complexes together, which exert pressure on the canvas and form protrusions.

"We're estimating that about 70% of all paintings have these soaps present in them," said Marc Walton, the co-director of the Center for Scientific Studies in the Arts at northwestern University, who was brought in to diagnose the O'Keeffe paintings.

"It doesn't mean it's progressed to deterioration, but it's a common problem in all paintings. There are 40 groups around the world trying to figure it out."

iPad diagnostics

Walton and his team have developed an iPad app to monitor the deterioration of paintings over time.

To assess a painting, all you have to do is hold an iPad in front of the art, and the technology will digitally strip away the colours and take a series of photos to render a 3D surface of the painting.

It can produce statistical measure based on its scans, and provide information such as the density, size and shape of a protrusion.

"With this, we can access art wherever we go," he said. "We can use it to see where soaps are forming on canvas and where they're not."

Walton suspects that humidity is the culprit behind the phenomenon.

"We need to correlate the environmental information with the measurements we're making to see the rates of deterioration taking place," he said. "If we understand the molecular point of view, then we might be able to tailor the museum environment to halt that process."


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