This is another sign of Leonardo’s genius
Study: A rare compound discovered in the Mona Lisa reveals a new secret
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Leonardo da Vinci was a painter, inventor, and anatomist, to name just a few of his talents—and now, one might add, he was an innovative chemist. It turns out the master artist was more experimental with the famous Mona Lisa than previously thought – and was likely the creator of a technique seen in works created a century later, a new study suggests.
Using X-ray diffraction and infrared spectroscopy, a team of French and British scientists discovered a rare mineral compound within the Mona Lisa. The discovery offers new insight into how the work dating back to the early 16th century was painted, according to the study recently published in the Journal of the American Chemical Society.
Along with white lead pigment and oil, a compound known as plumponacrite was found in the paint’s base layer. A study published in 2019 identified the metal in several of Rembrandt’s works from the 17th century, but researchers had not found it in works from the Italian Renaissance until this new analysis.
The rare plum compound is also found in the painting “The Last Supper” as well as several 17th-century Rembrandt works.
Plumponacrite forms when lead oxides combine with oil. According to the study, mixing these two materials on a palette is a technique used by later artists such as Rembrandt to help dry the paint. The discovery of this rare compound in the Mona Lisa suggests that Leonardo may have been the original pioneer of this approach, says Gilles Wallis, author of the latest study and a professor at the Sorbonne University in Paris, who also co-authored the 2019 report.
“Everything that comes from Leonardo is very interesting because he was an artist of course, but he was also a chemist and a physicist – he had a lot of ideas and he was an experimenter, trying to improve the knowledge of his time.” Wallis says.
“Every time you discover something in his operations, you discover that he was clearly ahead of his time,” Wallis adds.
Wallis explains that the Mona Lisa, like many other 16th-century paintings, was painted on a wooden board that required a thick substrate. Researchers believe that Leonardo mixed lead oxide powder with linseed oil to produce the thick layer of paint needed for the first coat, creating the rare compound without his knowledge.
Mona Lisa analysis
Currently, researchers are not allowed to take samples of the masterpiece, which is housed in the Louvre Museum in Paris and protected by glass, Wallis says. However, using a microscopic sample from 2007 taken from an area of the artwork directly behind the frame, scientists were able to analyze the paint using a high-tech machine called a synchrotron. The particle accelerator allowed the team to study the composition of the dye at the molecular level.
“These specimens have a very high cultural value,” Wallis highlights. “It is not possible to collect large samples from the plate, so a synchrotron is the best way to analyze them.”
According to the study, the substrate of Leonardo’s The Last Supper has the same chemical composition as the Mona Lisa, even though the fresco was painted on a wall. The scientists had a wide range of samples from the Last Supper to analyze — 17 in total — that came from paint that had peeled off the wall over time, Wallis says.
The Mona Lisa and The Last Supper are two of less than 20 known paintings painted by Leonardo during his lifetime. Over time, researchers hope to be able to discover more about the artist and his works.
“We’ve known for a long time that Leonardo was an inveterate experimenter,” says William Wallace, distinguished professor and chair of the Department of the History of Art and Architecture at Washington University in St. Louis.
“So it is not at all surprising to see him experimenting in other media, especially in light of his dedicated search for the best (often unconventional) drawing techniques to create his ‘living’ artworks,” says Wallace, an expert on art and architecture at Renaissance era, which did not participate in the study.
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