Paris, France – No name is as synonymous with the Renaissance as Leonardo da Vinci. More than a painter, architect, engineer, sculptor and scientist, da Vinci was an absolute intellectual titan of his time, introducing concepts and ideas that were centuries ahead of his time. In addition to its sheer brilliance, da Vinci is also rumored to have placed hidden meanings, puzzles, and messages in his works that require careful examination to identify. For example, the golden ratio is present in a series of his paintings.
Now, fascinating new research from the American Chemical Society has found that Da Vinci was probably experimenting with base layers. under his paintings. Researchers found that samples taken from two of his most iconic paintings, “Mona Lisa” and “The Last Supper,” show that the painter likely conducted experiments with lead(II) oxide that led to the formation of a rare compound he called plumbonacrite under the artwork.
The man may have lived and died centuries ago, but his works still inspire awe and have a certain air of mystery. The “Mona Lisa” has one strange way of looking at the spectators, and one cannot help but wonder how Da Vinci drew tanks and primitive flying machines in the 15th century. His writings and artwork have long been explored by scientists and scholars alike for hidden clues or meanings, and many of his paintings from the early 1500s (including the “Mona Lisa”) were painted on wooden panels that required a thick “ground layer”. of paint before adding the artwork.
Researchers have discovered that while other artists of the time often used plaster as a layer of soil, da Vinci went on his way stretching thick layers of white lead pigment and infusing his oil with lead(II) oxide, which is an orange pigment that would have imparted specific drying properties to the earlier painting.
da Vinci also used a similar technique on the wall below his iconic ‘Last Supper’, which was a notable departure from the traditional fresco technique predominantly used at the time. So, in an effort to further investigate these unique layers, Victor Gonzalez of Université Paris-Saclay, ENS Paris-Saclay and colleagues set out to apply up-to-date, high-resolution analytical techniques to small samples of two emblematic da Vinci paintings.
Finally, the research team carried out their analyzes on a small “microsample” that had previously been taken from a hidden corner of the “Mona Lisa”, in addition to 17 microsamples obtained from the surface of the ‘”Last Supper”. Then, via X-ray diffraction and infrared spectroscopy techniques, the study authors determined that the ground layers of the artworks contained not only oil and white lead, but also a much rarer compound: plumbonacrite (Pb5(Co3)O(OH)2).
This material has never been seen Italian Renaissance earlier paintings, but has been detected in later Rembrandt paintings created in the 1600s. Plumbonacrite is only stable under alkaline conditions, indicating that its formation resulted from a reaction between oil and lead oxide ( II) (PbO). Notably, still intact PbO grains were also seen in most of the “Last Supper” samples analyzed.
While painters and artists are known to add lead oxides to pigments to aid drying, this technique has not been experimentally demonstrated for Italian Renaissance paintings. Furthermore, when the study authors searched Da Vinci’s writings, the only evidence they found of PbO was in reference to skin and hair remedies – although today it is known to be quite toxic! Still, these findings at least suggest that lead oxides had a place in the Old Master’s palette and may have helped create some of the finest masterpieces we know today.
The to study is published in Journal of the American Chemical Society.
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