Art may be a window into the human condition, but as it turns out, art can occasionally develop a medical condition. One doesn’t usually think of works of art as getting ill, but as the work of American painter Georgia O’Keeffe demonstrates, art can indeed develop one mild skin condition… acne. And now a multidisciplinary team of researchers from Northwestern University and the Georgia O’Keeffe museum in Santa Fe have developed a tool to detect and monitor the strange lumps and bumps that have appeared in O’Keeffe’s paintings over the years.
The pin-sized blisters bubbling on the surface of the O’Keeffe’s work were apparent even in her lifetime. However, for decades conservationists and scholars assumed these tiny protrusions were grains of sand, kicked up from the New Mexico desert where she lived and worked. But as the protrusions began to grow, spread and eventually flake off, curiosity gave way to concern.
Researchers at Northwestern University discovered that these strange spots are not biological in origin like human acne, but chemical. The blemishes are the result of a chemical reaction between the metal ions found in many pigments and the fatty acids commonly used as binder in paints. The resulting reaction creates something fairly normal with a strange name: a metal soap.
From a chemical standpoint, soap is just a specific type of compound. In fact, soaps generally contain some sort of metal ion. The difference between the soap in our bathrooms and the bumps on the paintings, is that while toilet soaps have sodium or potassium as their metal ions, the ions in the metal soaps on the paintings are the much heavier zinc and lead ions. Zinc and lead are each used to produce white paint. While the paint is generally safe for artists to use, the same can’t always be said for the paintings themselves.
“The free fatty acids within the paint’s binding media are reacting with lead and zinc pigments,” said Marc Walton, a research professor of materials science and engineering in Northwestern’s McCormick School of Engineering. “These metal soaps started to aggregate, push the surface of the painting up and form something that looks like acne.”
Conservators have restored some of the paintings where the damage is more pronounced, but the protrusions continue to return.
Walton was part of a team that developed a new tool that can effortlessly map and monitor works of art. The tool enables researchers to carefully observe the protrusions in order to better understand what conditions make the protrusions grow, shrink or erupt.
“If we can easily measure, characterize and document these soap protrusions over and over again with little cost to the museum, then we can watch them as they develop,” said Oliver Cossairt, an associate professor of computer science in McCormick, who led the technology development. “That could help conservators diagnose the health and prescribe treatment possibilities for damaged works of art.”
The researchers have noted that unfortunately, nearly all of Georgia O’Keeffe’s paintings have some degree of damage from metal soap formation. While some of the cases of “acne” are in early stages of development and can only be viewed with ultraviolet imaging, others are more advanced and can be seen with the naked eye. Conservators have restored some of the paintings where the damage is more pronounced, but the protrusions continue to return.
They have also noted a correlation between how number of times the paintings have travelled to public exhibitions and the size and maturity of the surface disruption. The more times the paintings have travelled, the larger and more numerous the spots.
[…] while the soaps in our showers and sinks help us to keep acne away, in the fine art world, these soaps have the potential to spoil centuries worth of historical artwork.
The device the team has developed to monitor the condition of the paintings is like a ‘tricorder’ out of Star Trek. It is a pocket-sized device that can instantly scan the 3D structure of a painting’s surface using the LCD display and camera available on any smartphone. After the scan is made, the data is processed by sophisticated custom algorithms developed by Northwestern’s Aggelos Katsaggelos to determine the condition of the painting’s surface.
“We collect a lot of data in an efficient, successful way, but then the data needs to be processed,” said Katsaggelos, the Joseph Cummings Professor of Electrical Engineering and Computer Science at McCormick. “The technology uses machine learning to distinguish whether texture is a soap protrusion or something benign like a brush stroke. Then, for the protrusions, we extract statistics — the density, size and shape.”
The ultimate goal for the research is to ensure the painting’s safety and condition in years to come. Because many paintings across the centuries contain the same types of pigments and fatty acids, the formation of metal soap plagues paintings across art history. So while the soaps in our showers and sinks help us to keep acne away, in the fine art world, these soaps have the potential to spoil centuries worth of historical artwork.
“If we can solve this problem, we’re preserving our cultural heritage for generations to come,” Walton said.
This post was written by Miles Martin and edited by Karolina Zieba.
Editor’s note: The image shown is of a Gerogia O’Keeffe painting titled Music Pink and Blue II showcased at the Whitney Museum of American Art.
Correction: this article was edited on 05/03/19 by E.Mercer, correcting Georgia O’Keefe to Georgia O’Keeffe.