Copyright © 2019 Albuquerque Journal
A team from Santa Fe’s Georgia O’Keeffe Museum and Northwestern University studying the metal “soaps” in the artist’s paintings have developed an iPad app they say will streamline how conservators monitor the harmful bumps.
Soaps, in this case, are lead-based chemical reactions that occur between the binding materials in paint. They cause microscopic protrusions that cause a painting to deteriorate, creating problems including discoloration or pieces of paint coming off.
The Georgia O’Keeffe Museum has studied the soap-caused bulges in O’Keeffe’s paintings, which the painter herself first noticed back in the 1940s, for the past several years. Dale Kronkright, the museum’s head of conservation, approached the researchers at Northwestern about the issue and in late 2017, the team received a $350,000 National Endowment for the Humanities grant to further develop 3-D imaging technology and study what affects the rate of growth of soaps within the paintings.
The team’s current findings and the new app were presented last month at the American Association for the Advancement of Science’s annual conference.
But the problem of soaps in paintings is not exclusive to O’Keeffe.
“This is a major problem throughout the world,” said Marc Walton, research professor of materials science and engineering in Northwestern’s McCormick School of Engineering and co-director of the Center for Scientific Studies in the Arts, a joint effort between the university and the Art Institute of Chicago.
“It’s been recognized that soap-based degradation is one of the primary agents of decay on paintings and some 70 percent of all old paintings actually have these things on them,” Walton continued. “There’s a lot of research, chemical research, that’s going into understanding the reactivity, how they’ve self-assembled molecularly, and how they exert enough pressure on the surface of the canvas to be able to produce what we’re calling protrusions.”
According to Walton, simple tools to monitor soaps over time could improve conservators’ preventative efforts by helping determine whether the various environments paintings are kept in slow down or speed up the growth of soaps.
At least five O’Keeffe paintings have already required repairs due to significant soap damage. In 2017, Kronkright said about 95 percent of the Santa Fe museum’s O’Keeffe artwork shows some evidence of soaps.
Walton said he’s seen different types of soaps in paintings from as far back as 2nd-century Rome up to present-day works. But the most vulnerable paintings are believed to be those made just before or after World War II, Walton said, due to the commercialization of paints. More chemistry and additives went into manufacturing paints during that era in order to ensure the materials’ shelf life over a long period of time.
Through collaborating with the museum, Walton said the Chicago team realized how surface-shape measurements currently require “bulky,” expensive 3-D imaging equipment. A painting must be taken out of storage, transported with the help of a preparator and set up in a photo studio-like environment to take the images for the quantitative measurements. This difficult process can prevent the data from being taken at all, Walton said.
The way the new technology works, Walton explained, conservators can use an iPad tablet to illuminate and then take pictures of the painting’s surface. Through the app, images go to a server at the Northwestern campus that makes a 3-D image of the painting’s surface and processes the data.
The technology helps detect the protrusions, as well as their size and frequency. Conservators can compare the measurements to previous images to see which paintings are deteriorating quickly and which are not.
In a press release from Northwestern last month, Oliver Cossairt, associate professor of computer science at the university’s McCormick School of Engineering – who took the lead on creating the new technology – compared it to a “tricorder,” the fictional hand-held device from “Star Trek” used to scan places, objects and people to extract information.
“We’re able to basically pare down all this complex equipment into something that’s really simple,” said Walton.
“What’s nice about this is that you can take it anywhere, you can take it into deep storage, you can bring it to a work of art, and you can also just do it on the fly. You can capture data within two minutes, while, with the more complex device, which requires hand manipulation, it would take us two days to process all the data because it had to all be done manually. What we really did is optimize going from the capture all the way down to the processing so the entire sequence can take under two minutes.”
Kronkright said the technology produces a “normal vector map” that identifies unwanted protrusions, using bright or false colors to show different shapes and angles of direction.
“It’s in this normal vector map that these protrusions are clearly different than the artists’ brush strokes or the texture of the oil paint, dirt or chips,” Kronkright said. “It really makes it possible for the computer to say OK, I’m looking for little round interruptions in otherwise linear formations on a surface.”
This type of 3-D imaging technology has long existed in the larger machinery used previously, Kronkright emphasized, but making it available in a portable device is significant. The app provides conservators a rough look at a painting’s surface, which lets them decide quickly whether a painting needs to be looked at further with the high-resolution machinery or if it can get a “clean bill of health” for the time being. If a museum has a collection of tens of thousands of pieces that need to be preserved, staff must be selective about time and resources, he said. And realizing that a painting has problems early could prevent major issues down the line.
“Being able to capture a 3-D image using a portable device is akin to you going to your general practitioner for your annual checkup and your GP seeing a couple of moles and one doesn’t look quite right,” Kronkright explained. “So the GP takes a picture of that and sends it off to a dermatologist, and the dermatologist says, ‘Yeah that one’s not quite right, this person should come in for a more detailed examination.’ ”
The technology is meant to allow further study to determine external elements – humidity, temperature, light exposure are all potential factors – that could be contributing to a faster rate of soap growth. Or, conversely, Kronkright said, “What did we do right with this painting that we stopped the growth of soaps and how can we replicate that with the rest of the collection?”
The team plans to make the app available online for free, according to Walton. He said the group will have to release it by December under terms of the NEH grant.
Over the next year, the team wants to increase the technology’s machine-learning capabilities so it can register one image on top of another to compare images of specific area of a painting over time.
Kronkright added that, eventually, he wants conservators around the world to be able to compare images made with the app.
Walton added that he’s interested in seeing what other application the imaging technology could have down the line. For example, the app could be used to analyze the surface of currency and look for forgeries
Dissecting her materials
The ongoing research has also led to important developments over the past year about the soaps and their growth, according to Walton and Kronkright.
Walton said researchers have established a connection between commercial, primed canvases that O’Keeffe was using, which they found in the garage of her Abiquiú home, and the soap protrusions on her paintings between 1940 and 1950. Walton said the researchers noticed similar bumps on those old unused canvases.
A focus of the research going forward will be to determine what exactly was added to materials that O’Keeffe used that might be causing the chemical reaction issues. In particular, Walton said the team is still looking to determine whether aluminum stearate – a synthetic fat that is used in paints to keep them more “flexible” over a long period of time – is the culprit in this case.
“What’s interesting about this is if O’Keeffe used this canvas, there’s probably a lot of other artists that used this same commercial product,” said Walton. “And then the question arises, if we see the same protrusions and soaps forming on those paintings by other artists, if we can start to make that connection, we can actually solve a lot of conservation issues when it comes to groupings of paintings made during this time period.”
Something the O’Keeffe conservators have long noticed is the correlation between her paintings with high soap growth rates and how often those paintings have traveled. What they don’t know, Kronkright said, was what specific environmental changes could be causing soap growth.
Kronkright said the types of materials used in O’Keeffe paintings have recently been undergoing lab study in which the environmental factors were accelerated to see what could be helping or hurting her works.
Initial results have shown changes in humidity have some kind of effect, he said.
“Essentially, moisture, water molecules moving through the oil film every time the humidity changes, that seems to correlate with an increase in number and size,” said Kronkright. He noted that the museum designed and patented a frame a few years ago that acts as a “humidity-sealed container” and stabilizes the painting’s moisture as it travels. Surface shape imaging will be able to determine what kind of impact that is having.
Though the soaps issue is widespread throughout the world, Walton noted that the reason the O’Keeffe’s collection is the prime studyset is because the Santa Fe museum has not only her paintings, but also the materials she used to create them. Her brushes, paint tubes and canvases have been kept.
And Kronkright also said she was incredibly consistent in her use of materials – she used only a small handful of canvas types and paint colors throughout her 60-year career. O’Keeffe herself also kept records of when and where her paintings traveled. This allows for a level of study that isn’t possible with other famous artists.
“It’s extremely important to focus on someone like Georgia O’Keeffe, where we have everything in one place, and then use that as a model to apply to all the other artists where these problems are exhibited,” Walton said.