The famous “Mona Lisa” has revealed another secret. By utilizing X-rays to delve into the chemical structure of a tiny fragment of this iconic artwork, scientists have garnered new insights into the techniques Leonardo da Vinci employed to create his groundbreaking portrait of the woman with the subtly enigmatic smile.
The research, published on Wednesday in the Journal of the American Chemical Society, hints that the famously curious, educated, and inventive Italian Renaissance master might have been in an especially experimental mood when he embarked on the “Mona Lisa” project in the early 16th century.
Unique Oil-Paint Recipe Discovered
The oil-paint recipe Leonardo utilized as his base layer to prepare the panel of poplar wood seems to have been distinct for the “Mona Lisa,” with its own unique chemical signature, discovered by a team of scientists and art historians in France and Britain.
“He was someone who loved to experiment, and each of his paintings is completely different technically,” said Victor Gonzalez, the study’s lead author and a chemist at France’s premier research body, the CNRS. Gonzalez has examined the chemical compositions of dozens of works by Leonardo, Rembrandt, and other artists.
“In this case, it’s interesting to see that indeed there is a specific technique for the ground layer of ‘Mona Lisa,'” he conveyed in an interview with The Associated Press.
Specifically, the researchers discovered a rare compound, plumbonacrite, in Leonardo’s first layer of paint. This discovery, according to Gonzalez, confirmed for the first time what art historians had only hypothesized before: that Leonardo likely used lead oxide powder to thicken and help dry his paint as he began working on the portrait now viewed from behind protective glass in the Louvre Museum in Paris.
Carmen Bambach, a specialist in Italian art and curator at New York’s Metropolitan Museum of Art, who was not involved in the study, labeled the research “very exciting” and mentioned that any scientifically proven new insights into Leonardo’s painting techniques are “extremely important news for the art world and our larger global society.”
The detection of plumbonacrite in the “Mona Lisa” testifies “to Leonardo’s spirit of passionate and constant experimentation as a painter – it is what renders him timeless and modern,” Bambach communicated via email.
A Glimpse into Renaissance Paint Techniques
The paint fragment from the base layer of the “Mona Lisa” that was analyzed was barely visible to the naked eye, no larger than the diameter of a human hair, and came from the top right-hand edge of the painting.
The scientists peered into its atomic structure using X-rays in a synchrotron, a large machine that accelerates particles to nearly the speed of light. This enabled them to unravel the speck’s chemical makeup. Plumbonacrite is a byproduct of lead oxide, allowing the researchers to assert with more certainty that Leonardo likely used the powder in his paint recipe.
“Plumbonacrite is really a fingerprint of his recipe,” Gonzalez noted. “It’s the first time we can actually chemically confirm it.”
Following Leonardo, Dutch master Rembrandt might have employed a similar recipe during his painting tenure in the 17th century; Gonzalez and other researchers had previously discovered plumbonacrite in his work as well.
“It tells us also that those recipes were passed on for centuries,” Gonzalez said. “It was a very good recipe.”
It’s believed that Leonardo dissolved lead oxide powder, which bears an orange color, in linseed or walnut oil by heating the mixture to produce a thicker, faster-drying paste.
“What you will obtain is an oil that has a very nice golden color,” Gonzalez stated. “It flows more like honey.”
Yet, the “Mona Lisa” – said by the Louvre to be a portrait of Lisa Gherardini, the wife of a Florentine silk merchant – and other works by Leonardo still have other secrets awaiting discovery.
“There are plenty, plenty more things to discover, for sure. We are barely scratching the surface,” Gonzalez said. “What we are saying is just a little brick more in the knowledge.”
With information from CBS News