X-Rays Reveal Details of Portrait Once Hidden Under Vesuvius’ Ash

Using X-ray fluorescence, researchers have mapped the pigments used on a crumbling painting in Herculaneum

Herculaneum Portrait
Roberto Alberti, Ph.D

In 79 A.D., the Roman city of Herculaneum was engulfed in flood of molten mud, rock and gas in the same volcanic eruption of Mount Vesuvius that destroyed its more famous neighbor, Pompeii. When researchers began excavating the city in the 19th century, they found mosaics and paintings. Since they were uncovered, however, the succeeding decades of weather and exposure to contaminants in the air have led many of these artworks to further deteriorate. But Jen Viegas at Seeker reports that a new method of analyzing those paintings may help researchers preserve and even restore the artworks.

Researchers recently used a portable macro X-ray fluorescence instrument called ELIO to peel back the layers of dirt and ash on a painting of a young woman in Herculaneum’s House of the Mosaic Atrium.  By placing the instrument about half an inch away from the painting, the researchers were able to noninvasively map elements in the painting like iron and copper.

“As far as we know, this is the first study of an ancient Roman wall painting — or any other historical wall painting — in situ, in its original setting,” leader of the study Eleonora Del Federico, a professor of chemistry at the Pratt Institute, tells Viegas. “The technique is fairly new, and has been used for studies at museums on Rembrandts, Picassos and Van Goghs, among others.”

According to a press release, the analysis revealed that the artist sketched the young woman using an iron-based pigment. The areas around the woman’s eyes were highlighted using a lead-based paint. Signs of potassium around her cheeks indicate that a green earth-based pigment was used to create a flesh color.

While the painting is faded and crumbling, knowing the elements that are still in the painting could help conservators choose the right cleaning solvents and other chemicals to helps preserve and restore what is there. And while painting over old artworks is frowned upon these days, over at ForbesSam Lemonick reports the data researchers uncovered could be used to recreate the portrait digitally.

With the first test of ELIO in Herculaneum looking like a success, Del Federico tells Lemonick she hopes it’s not the only analysis she does in the ancient city. “So many frescoes are considered gone. Now this technique has the potential to see other frescoes that you can’t see with the naked eye,” she says.

The same technique is being used to explore the works of master painters to understand how they made their images in layer-by-layer detail. While in the past, artworks had to be transported to particle accelerators to get a glimpse under the surface layer—an even more expensive process, which carries an inherent risk—just last year, the portable process was able to safely help researchers figure out that white blotches on Edvard Munch’s “The Scream” was candle wax (not bird droppings as some people thought). The technique was also recently used to help conservators as they restored Hans Memling's “Christ with Singing and Music-Making Angels” in Antwerp.

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