Conservators Rush to Save 20th-Century Masterpieces

What art conservator Dale Kronkright discovered that day in 2000 would set off alarm bells in art museums around the world.

As head of Conservation for the Georgia O’Keeffe Museum in Santa Fe, New Mexico, the museum had only been open for three years, when he began to notice small grains in the paintings, not uniform in shape or appearance. As a result, these particular O’Keeffe paintings began to look darker, the colors less vibrant. “I asked some of the curators about it and they told me it was thought that O’Keeffe added sand to some of her paintings when she moved to the area,” he says.

But the grains were appearing in her earlier works as well, the ones O’Keeffe had painted while in New York. Kronkright also noticed that grains were appearing in the tacking edges of the painting, where the canvas had been stretched to meet the frame. It didn’t make sense that O’Keeffe would have added sand here, so Kronkright decided to take a closer look.

When he did, he found the grains were not grains at all, but, instead, tiny protrusions, which had begun to explode outward, or implode inward, giving the painting’s surface a blistered, pitted appearance—and there were sometimes thousands of these miniature eruptions all over the canvas.

So what, he wondered, was causing these protruding blisters?

It turns out it was the 20th-century materials—and 20th-century improvements that manufacturers had made to them—that were now causing a problem. At least two of these improvements had come together to create what turned out to be a “perfect storm” of destruction.

“Early paints were simple combinations of pigment and drying oils,” Kronkright explains. The problem was, these elements would not stay evenly distributed in paint tubes. Pigment would separate from the oil and settle in the bottom, and that meant 19th-century artists had to go through a laborious process of grinding and re-mixing paint once a tube was opened. As early as the 1920s, however, paint manufacturers had found a solution. They added to the paint a component known as aluminum stearate, a type of aluminum soap, which “jellified” the oil, making separation of the pigment more difficult.

But aluminum stearates were only part of the problem.

During the 20th century, commercially-prepared canvases began to change as well. More white lead pigment was added to canvases to promote faster drying. What manufacturers didn’t know at the time was that the additional lead in the canvas would react chemically with the aluminum stearate now being added to paint, so that, over time, the paint would begin to separate from the surface, creating tiny blisters.

“You can see the blisters with the naked eye,” says Kronkright. “They’re the size of a human hair.” But there is no easy way to understand just how much damage a painting has sustained without sitting down with a microscope and counting each of the blisters on a painting.

“That’s when we decided to ask for help,” says Kronkright.

Although the O’Keeffe Museum had been monitoring its collection through imagery since 2011—snapping high-grade images of paintings using multiple sources of light—the blistering problem meant the museum was going to need better, more complete pictures of the damage that was being inflicted.

“We partnered with the Art Conservation Center, run by Northwestern University and the Art Institute of Chicago, on a two-year project to develop a 3-D imaging technology that could help us better assess the growth of the protrusions,” Kronkright says.

This 3-D imagery will record the paintings under various light frequencies, to determine several things. First, it will help conservators determine the painting’s chemical composition. In the past, information about an artwork’s composition would mean removing a postage-stamp size piece from the painting itself. The new technology renders that step unnecessary. Second, the new technology will provide a layered, three dimensional look at the painting, and finally, it will allow for side-by-side photographic and data comparisons of the artwork both now and in the future. This advantage means conservators will be able to track the damage over time. “An algorithm can be written that will allow a computer to assess the damage and provide digital data, much more quickly and quantitatively than a conservator could,” Kronkright says.

“Our intention is to create a Web-based system that will allow art conservators around the world to upload and analyze images of paintings in their collections, so they can see if similar problems are occurring in their works of art,” he says.

After all, most 20th-century painters were working with similar materials. That means that any 20th-century work of art is subject to the same kind of damage that has been found in the O’Keeffe paintings.

Now that conservators have pinpointed the problem, the next question becomes: how can these paintings be preserved?

“Right now, we’re unsure how to do it,” says Kronkright. “The idiosyncrasies of paint manufacturers mean we haven’t been able to quantify anything yet.” But the fact that he is working with the art of a single painter, means he has certain advantages in a search for a solution. “Much of the history of O’Keeffe’s paintings is known,” he says.

For example, there is plenty of documentation that shows which O’Keeffe paintings have traveled to different exhibits and shows. “The flower paintings have traveled the most,” Kronkright says. “We’ve found that the more extensive the painting’s travel history, the more numerous and mature the blisters.”

“In O’Keeffe’s time, when paintings were shipped for an exhibit, they were framed, put in a crate then taken by train to a truck distribution station, and the crates were transported from there to the exhibit space. The paintings went through a range of temperature and humidity changes. Today, of course, we have temperature-controlled fine-art transportation trucks, but even then, environmental changes can occur,” says Konkright.

Any time temperatures rise over 85-degrees, for example, aluminum stearate goes from a solid to a liquid form, and, as a fluid, migrates through different layers of the painting.

The O’Keeffe Museum has found a way to create a microclimate, both within and outside the frame, to prevent environmental issues from harming the painting. “We have eight different profiles we use, including more thermal insulation, and a humidity buffer that helps to control the temperature and humidity,” Kronkright says.

Those kinds of precautions will help. And knowing which paintings need extra preservation efforts will also help.

“The world of art conservators is small,” says Kronkright. “There is awareness around the world in Europe and Asia as well as all parts of the U.S. of our efforts to create 3-D imaging technology. Right now, all of us are just waiting for it to happen.”