WASHINGTON, D.C. — Like a teen’s skin, oil paintings can break out in zits. Researchers want to prevent these flare-ups, which can damage priceless art. A group of scientists has now developed a computer program to track these bumps.
Artists and museum experts have known for many years that oil paintings can form tiny blisters. As these bumps grow, the surface paint can crack and flake off like dry skin. Georgia O’Keeffe was an early modern painter in the United States. She had noticed those breakouts on her own artwork. Some people suspected the bumps came from her studio in New Mexico. Desert sand might have mixed with her paints as she worked.
Now researchers have identified the true culprit. Chemicals in the paint react to make metal soaps. Such metal soaps form beneath the surface of some 70 percent of all oil paintings. Art experts have seen them on works by Rembrandt, Francisco de Goya and Vincent van Gogh.
“It’s not an unusual phenomenon,” says Marc Walton. This art expert is a materials scientist at Northwestern University in Evanston, Ill. Walton discussed the metal-soap problem during a press conference, here, at the annual meeting of the American Association for the Advancement of Science.
Roughly 20 years ago, scientists learned what makes metal soaps. Oil paints are a mix of fats, pigments and metal ions. The negatively charged fats can react with positively charged metal ions (such as zinc and lead). These form tiny structures known as liquid crystals. These bits eventually gather into globs that look like tiny white insect eggs. Over time, those apparent eggs slowly grow until they bulge under the paint layers. Eventually, the surface paint can tear and flake off.
Walton wants to figure out what makes these liquid crystals form. Could dampness, light or temperature make a difference? To find out, he needed to be able to study the paintings’ bumps.
He turned for help to computer scientist Oliver Cossairt, also at Northwestern. Cossairt designed a computer program. It can run as an app on a cell phone or tablet. The app will direct the device to shine patterns of light onto a section of some artwork. Then the device’s camera collects the light reflecting off the paint.
Color can camouflage the small distortions caused by the bumps. So the program strips away the color. Then the software sorts the knobby structures and separates them from other textures, such as brushstrokes. Later, the app creates a report that lists the place and size of the acne-like blisters and how they’re grouped.
It’s a bit like Star Trek’s “tricorder,” Cossairt says. That device could diagnose a human illness from a simple scan. This one diagnoses chemical “disease” in artists’ paint.
Using the computer program, the team is now studying test paintings. Each one is exposed to one factor: light, humidity or temperature. The team wants to see how the fast an artwork’s zits develop and grow under these different conditions.
It’s hard for people working in museums to identify how quickly this art acne forms. “You see paintings with this kind of knobby, bubbly surface, and you don’t know if that has happened in five years, 50 years or more,” notes Kenneth Sutherland. He works at the Art Institute of Chicago in Illinois and did not take part in this study. Imaging could help researchers watch the bubbles and learn how to control or limit them, he says.
Scientists may never fully understand how metal soaps form. But this new app could help art conservators protect iconic works of art. As new bubbles on a painting emerge, the museum could move the artwork to a safer environment.
Oil paintings may always be prone to forming these zits, Walton says. The real solution might just be finding the best way to store the vulnerable works of art.
acne A skin condition that results in red, inflamed skin, commonly called pimples or zits.
American Association for the Advancement of Science (or AAAS) Formed in 1848, it was the first permanent organization formed to promote the development of science and engineering at the national level and to represent the interests of all its disciplines. It is now the world’s largest such society. Despite its name, membership in it is open to anyone who believes “that science, technology, engineering, and mathematics can help solve many of the challenges the world faces today.” Its members live in 91 nations. Based in Washington, D.C., it publishes a host of peer-reviewed journals — most notably Science.
annual Adjective for something that happens every year.
app Short for application, or a computer program designed for a specific task.
camouflage Hiding people or objects from an enemy by making them appear to be part of the natural surroundings. Animals can also use camouflage patterns on their skin, hide or fur to hide from predators.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
computer program A set of instructions that a computer uses to perform some analysis or computation. The writing of these instructions is known as computer programming.
conservator A person in charge of protecting and/or restoring valuable items.
develop To emerge or come into being, either naturally or through human intervention, such as by manufacturing.
diagnose To analyze clues or symptoms in the search for their cause. The conclusion usually results in a diagnosis — identification of the causal problem or disease.
environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).
factor Something that plays a role in a particular condition or event; a contributor.
fat A natural oily or greasy substance occurring in plants and in animal bodies, especially when deposited as a layer under the skin or around certain organs. Fat’s primary role is as an energy reserve. Fat also is a vital nutrient, though it can be harmful if consumed in excessive amounts.
humidity A measure of the amount of water vapor in the atmosphere. (Air with a lot of water vapor in it is known as humid.)
ion (adj. ionized) An atom or molecule with an electric charge due to the loss or gain of one or more electrons. An ionized gas, or plasma, is where all of the electrons have been separated from their parent atoms.
lead A toxic heavy metal (abbreviated as Pb) that in the body moves to where calcium wants to go (such as bones and teeth). The metal is particularly toxic to the brain. In a child’s developing brain, it can permanently impair IQ, even at relatively low levels.
liquid crystal A liquid made from an organic (carbon-based) material. Its physical structure consists of loosely ordered arrays of its molecular building blocks. Although a liquid, these arrays seem to resemble the ordered lattice seen in true, solid crystals. Also like true crystals, the liquid can refract light in ways that do not look the same from all directions.
materials science The study of how the atomic and molecular structure of a material is related to its overall properties. Materials scientists can design new materials or analyze existing ones. Their analyses of a material’s overall properties (such as density, strength and melting point) can help engineers and other researchers select materials that are best suited to a new application.
metal Something that conducts electricity well, tends to be shiny (reflective) and malleable (meaning it can be reshaped with heat and not too much force or pressure).
phenomenon Something that is surprising or unusual.
pigment A material, like the natural colorings in skin, that alter the light reflected off of an object or transmitted through it. The overall color of a pigment typically depends on which wavelengths of visible light it absorbs and which ones it reflects. For example, a red pigment tends to reflect red wavelengths of light very well and typically absorbs other colors. Pigment also is the term for chemicals that manufacturers use to tint paint.
software The mathematical instructions that direct a computer’s hardware, including its processor, to perform certain operations.
zinc A metallic element that in its pure form is ductile (easily deformed) and that is an essential micronutrient in plants and animals.
zits A colloquial term for the pimples caused by acne.