What secrets might be hiding beneath the surface of a masterpiece revered for centuries? The latest research into Leonardo da Vinci’s Mona Lisa has yielded a discovery that is as technically fascinating as it is historically significant: the identification of plumbonacrite, a rare lead compound, in the painting’s foundational layer. This discovery, made using cutting-edge synchrotron X-ray techniques, not only sheds light on Renaissance breakthrough chemistry but also suggests the handing down of artworks’ recipes from generation to generation.
A group of researchers headed by Victor Gonzalez at Université Paris-Saclay, working together with France’s National Center for Scientific Research, examined a microsample from the Mona Lisa’s top right corner about as wide as a human hair. With the assistance of high-angular resolution synchrotron X-ray diffraction and micro-Fourier transform infrared spectroscopy, the scientists revealed an unusual combination of highly saponified oil containing high concentrations of lead with a lead white pigment significantly lacking cerussite. The most surprising finding was the formation of plumbonacrite (Pb₅(CO₃)₃O(OH)₂), a previously unseen compound in Italian Renaissance paintings.
The occurrence of plumbonacrite is more than a chemical anomaly. It is only stable in basic surroundings and precipitates as a byproduct when lead(II) oxide (PbO) is combined with oil a method that dries the paint and thins it. As inorganic chemist Gilles Wallez, a participant in the research, said, “You understand easily when you analyze his pigments and his compositions that he was truly an experimenter.” This pioneering method contrasts with more prevalent utilisation of gesso or plain lead white priming by Leonardo’s contemporaries.
Technical accomplishment at identifying such trace amounts of plumbonacrite depended upon the unique abilities of synchrotron radiation. Unlike traditional X-ray sources, synchrotrons can produce tightly focused, tunable beams down to the micrometer level so scientists can test the atomic structure of paint chips without harming the artwork. As Koen Janssens of the University of Antwerp explains, When you want to do very laterally resolved analysis, you need very small beams to excite the material only at a specific location on the sample… to obtain those beams you need a synchrotron.
This finding has broad implications for both art history and conservation science. The same unusual compound has been discovered in the impasto layers of Rembrandt’s paintings, indicating a technical knowledge tradition passed down from Leonardo’s Renaissance experiments to the Dutch Golden Age. As Gonzalez writes, “It tells us also that those recipes were passed on for centuries.”. Actually, it was a very good recipe. The existence of plumbonacrite in the Mona Lisa and Rembrandt’s paintings gives both works a chemical signature that could be used to authenticate paintings and trace back the development of art materials.
The examination also highlights the need for multi-analytical strategies in art preservation. Methods of X-ray fluorescence (XRF), infrared spectroscopy, and scanning electron microscopy make it possible to identify pigments and binders in layers, not just the artist’s color palette, but even the order of creative choices. These techniques are now essential for authentication, restoration, and the comprehension of historical pigment degradation, as illustrated in research on Van Gogh’s sunflowers and Goya’s overpainted portraits.
In the case of the Mona Lisa, the identification of plumbonacrite is not only evidence of Leonardo’s relentless experimentation but also of the fact that the most famous works of art are, at heart, the products of both creative genius and material science. As Carmen Bambach of the Metropolitan Museum of Art noted, this study testifies “to Leonardo’s spirit of passionate and constant experimentation as a painter it is what makes him timeless and modern.”
With each successive analytical breakthrough, more mysteries are uncovered from the depths of these masterworks. As Gonzalez puts it, “There are plenty, plenty more things to discover, for sure. We are barely scratching the surface.”
