The portrait of the dead woman is nearly 2000 years old, but it shines with brilliant detail. The subject’s eyes are huge and dark, her brows thick, her mouth plump. Brightly colored necklaces are wrapped around her neck, and her robes are a rich purple. At some point in the 2nd century C.E., this painting was likely commissioned to adorn the mummified body of a noblewoman in ancient Egypt, preserving her likeness for eternity. And now, scientists are using a new imaging technique to uncover the work’s secrets.
The painting, housed at the National Gallery of Art in Washington, D.C., is one of about 1,000 so-called "Fayum portraits"—mummy masks created around the 1st-3rd centuries C.E. during Egypt's Roman era—that exist in museum collections today. Fayum portraits, which get their name because they are most commonly found in Egypt's Fayum region, combine Egyptian and Greco-Roman styles, and they are fascinating to art historians because they are believed to depict real people—and they are incredibly life-like.
While the National Gallery's Fayum portrait is in relatively good condition, experts had questions about it that could not be answered by simply observing the work with the naked eye: What types of pigments were used by the ancient artist? Were the pigments pure or mixed? What materials were used to bind the paint?
Hoping to shed light on this centuries-old artistic process, scientists from the National Gallery and the University of California, Los Angeles came together to analyze the Fayum portrait with new a technique that they have dubbed “macroscale multimodal chemical imaging.”
The pioneering approach combines three existing technologies—hyperspectral diffuse reflectance, luminescence and X-ray fluorescence—to create a highly detailed map of the portrait’s chemical features, which in turn reveals previously unknown information about how painting are made.
Spectroscopic techniques have been used in the past to individually for looking at specific, single points in an artwork. But by integrating three different technologies, the team of National Gallery and UCLA researchers was able to extend point measurements to scan the Fayum portrait, creating maps of molecular and elemental data for every pixel across its surface.
“When combined, these techniques are extremely, powerful,” Ioanna Kakoulli, a professor of materials science and engineering at UCLA, tells Smithsonian.com. “This [analysis] can help deconstruct ancient technology by unambiguous identification of the materials constituting the object under investigation.”
Crucially, the new imaging technology is non-invasive; researchers were able to glean a wealth of insight into the Fayum portrait without removing a single sample of paint. Their results, published in the journal Scientific Reports, reveal that the artist who created the image possessed a high degree of skill, mixing together different materials to produce a range of vibrant colors: red ochre and lead for the skin tone, charcoal black and the mineral natrojarosite for the green-yellow background, iron earths and other pigments for the woman’s hair. Based on variations in the surface of the portrait, researchers could also determine that the painter had applied the paint with three different tools: most likely a fine-hair brush, an engraver’s tool and a metal spoon.
Experts want to know information about a painting’s composition for two reasons, John Delaney, a senior imaging scientist at the National Gallery of Art, explains in an interview with Smithsonian.com. “One, for conservation purposes,” says Delaney. “If you're doing interventions, it's nice to know what's there … And the other thing is working out the technology of how these people were constructing [ancient artworks].”
Among other significant finds was the fact that melted beeswax had been widely distributed throughout the work. This indicated that the artist had relied on a technique known as “encaustic painting,” which involves mixing wax with pigments to create a paste-like paint. Prior to the analysis, researchers had suspected that the portrait was made in the encaustic style, like many other Fayum paintings. Spectroscopy helped confirm that their hunch was correct.
Other discoveries were more surprising. As Kakoulli points out, the artist seems to have drawn inspiration from real-life scenarios. The vibrant purple of the woman’s robe, for example, was created with madder lake, a natural pigment that was widely used to dye textiles. To render the green gems of her necklace, a copper salt was mixed with heated beeswax—the same process described in ancient manuals that offered guidance on tinting stones so they resembled real gems.
“I have found this extremely interesting,” Kakoulli says, “and amazing that we could achieve this [knowledge] without having to take any samples from the painting.”
Prior to their analysis of the Fayum portrait, researchers had successfully applied macroscale multimodal imaging to old masters paintings. But they were particularly keen to try out the new technology on an ancient painting, as centuries-old artworks are so fragile and precious that examining them can be extremely difficult or impossible.
“Often these are unique objects and curators do not allow sampling,” Kakoulli says. “If they do, sampling is very limited.”
Researchers have shown that non-invasive imaging can provide robust information about ancient artistic methods. Moving forward, they hope to adapt macroscale multimodal imaging so that it is more accessible to experts who study things like wall paintings and tomb art—ancient works that are not confined to the walls of a museum collection.
“The question is, how do we take this technology, which exists in the rarified atmosphere of our laboratory, and make it into practical equipment that you can take to the field?” Delaney says. “That's the next step.”