Researchers dust fine art for soot damage

Painted carvings in a cave temple in China were cleaned in 1986 (right), but atmospheric pollutants faded them only five years later

May 24, 2000
Web posted at: 12:09 p.m. EDT (1609 GMT)

By Environmental News Network staff

Fine art never dies, but pollution can cause it to fade.

Soot from the atmosphere readily accumulates on paintings, causing images to darken over time. Because the particles are so tiny, air filters often don't stop them from invading a gallery or museum.

How long it takes the tiny airborne particles to become visible on artwork is the subject of a recent study published in Environmental Science and Technology. The research supply museums with the information they need to clean and how to protect a valuable collection.

The researchers measured soot deposition in five Southern California museums. Using a laser printer that randomly deposited microscopic dots on colored samples, they developed tests to determine how long it takes the human eye to detect a difference in appearance.

More than 12 percent of an image must be covered with dots in order to perceive a difference between a clean and soiled surface, the researchers found. But when clean and dirty samples were placed side by side, the difference was much easier to discern.

According to the study, soot particles may remain invisible for up to 500 years. The time frame varies depending on the type of art.

Contemporary art is particularly susceptible to soot because the texture of the finished product is apt to be rougher and more porous. "Contemporary painting tends not to be varnished and is more absorptive to soot," said Jim Drunzic, a senior scientist with the Getty Conservation Institution.

Writing on the wall: documentation for Leon Bellan's laboratory tests on soiled surfaces

"Just because the soot is not visible does not mean it cannot cause damage," said Leon Bellan, lead author of the study. Consisting of fine black particles emitted from spent fossil fuels, soot is almost impossible to remove without damaging the surface of an image, he added.

Bellan noted that "even if (soot) is visible after 100 years, it is a problem because, at least in theory, we want to preserve the artwork for a very, very long time."

Everything from lighting to ground maintenance to gallery traffic contributes to the accumulation of soot, said Drunsic.

Museums farther removed from traffic had slower rates of accumulation, the study showed. For example, rates at the Getty Museum in relatively smog-free Malibu, California, were 20 percent slower than at the Norton Simon Museum in smog-choked Pasadena, California.

Government regulations could ensure a clearer picture for fine art. The Environmental Protection Agency has proposed more stringent emissions controls on diesel trucks. If the regulations are adopted, emissions of soot would be reduced by 110,000 tons each year.

Copyright 1999, Environmental News Network, All Rights Reserved

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The Environmental Science and Technology journal
Black soot deposition
The Environmental Protection Agency

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