Mona Lisa's Hidden Secrets: X-ray and Infrared Analyses Reveal Leonardo da Vinci's Palette

In a study published in the Journal of the American Chemical Society, researchers from Université Paris-Saclay, led by corresponding author Victor Gonzalez, unveiled the hidden secrets of Leonardo da Vinci's palette through the examination of a microsample from the ground layer of the world-famous painting, the Mona Lisa. This analysis sheds new light on the techniques and materials used by the Renaissance master.

The research, conducted through high-angular resolution synchrotron X-ray diffraction and micro Fourier transform infrared spectroscopy (FT-IR), offered an unprecedented glimpse into the composition of the painting's ground layer.

The microsample revealed a unique combination of strongly saponified oil with a high lead content, along with a cerussite-depleted lead white pigment. Most notably, the presence of plumbonacrite, a rare compound stable only in an alkaline environment, left a remarkable signature. It suggests that Leonardo da Vinci had embarked on a quest to create a thick paint suitable for covering the wooden panel of the Mona Lisa. He achieved this by treating the oil with a significant load of lead II oxide (PbO).

What makes this discovery all the more intriguing is the ambiguity in Leonardo's manuscripts concerning the use of PbO. The analysis of fragments from another masterpiece, the Last Supper, further substantiates that PbO was indeed a part of Leonardo's palette. The team detected both litharge (α-PbO) and massicot (β-PbO), along with plumbonacrite and shannonite (Pb2OCO3), marking the first-ever detection of the latter in a historical painting.

The researchers sampled a tiny paint fragment from the hidden barb of the ground layer in the upper right zone of the Mona Lisa, concealed by the frame. The sample was embedded in resin for microscopic studies, and a smaller fragment was preserved unembedded in a glass capillary for synchrotron radiation high-angular resolution X-ray powder diffraction (SR-HR-XRPD).

For the analysis of fragments from the Last Supper, the research team employed synchrotron radiation-based attenuated total reflectance micro Fourier transform (ATR-μ-FTIR) and micro X-ray powder diffraction (SR-μ-XRPD) techniques. These revealed a comprehensive view of the materials used in this iconic artwork.

The discovery of plumbonacrite in the Mona Lisa's ground layer represents a significant leap forward in understanding Leonardo's artistic techniques. It not only adds to our knowledge of his palette but also deepens our appreciation of the genius behind the enigmatic smile of the world's most famous painting.

This groundbreaking research reaffirms that, even centuries after their creation, Leonardo's masterpieces continue to reveal new facets of his artistic brilliance.

This article was written with the help of artificial intelligence and has been edited to ensure accuracy and clarity. You can read more about our policy for using AI here.

Reference

Gonzalez, V.; Wallez, G.; Ravaud, E.; Eveno, M.; Fazlic, I.; Fabris, T.; Nevin, A.; Calligaro, T.; Menu, M.; Delieuvin, V.; Cotte, M. X-ray and Infrared Microanalyses of Mona Lisa’s Ground Layer and Significance Regarding Leonardo da Vinci’s Palette. J. Am. Chem. Soc. 2023, April 9, 2023. DOI: 10.1021/jacs.3c07000