How did Leonardo da Vinci manage to paint such perfect faces? For the first time, a quantitative chemical analysis has been done on seven paintings from the Louvre Museum, including the Mona Lisa, without extracting any samples. The technique used shows the composition and thickness of each layer of material laid down by the painter, revealing that, in the case of glazes, thin layers of 1 to 2 μm have been applied. X-ray fluorescence spectrometry was performed directly on several paintings by Leonardo da Vinci that are displayed at the Louvre in Paris. (Image: V.A. Solé/European Synchrotron Radiation Facility) Leonardo's paintings fascinate, partly because of a range of subtle optical effects that blur outlines, soften transitions and blend shadows like smoke. Known as sfumato, this technique not only is the result of the genius of the artist but also of technical innovations at the beginning of the 16th century. Minute observations, optical measurements and reconstitutions have already described the sfumato, but new analysis can confirm the procedure of this technique, especially related to how the gradation is done. The study, led by the team of Philippe Walter of the Laboratoire du Centre de Recherche et de Restauration des Musées de France (LC2RMF, CNRS/Ministère de la culture et de la communication), with the collaboration of the European Synchrotron Radiation Facility (ESRF) and the support of the Louvre Museum, was published recently in Angewandte Chemie International Edition. This is a representation of the superposition of layers in paintings in the face of the Mona Lisa, on one light zone near the nose and the darker shadow of the hair. (Right) After treating the data, the thickness and concentration of pigments in the different layers are determined. (Image: Centre de Recherche et de Restauration des Musées de France) For the first time, Walter and his team, in collaboration with the ESRF and the Louvre, have brought new insight on the sfumato, thanks to a quantitative chemical study of the painted layers. Seven paintings by Leonardo have been analyzed without extraction, directly in the rooms of the Louvre (Virgin of the Rocks, Mona Lisa, Saint John the Baptist, Annunciation, Bacchus, Belle Ferronnière and The Virgin and Child with Saint Anne). The scientists concentrated on the study of the faces because they have the characteristics of the sfumato. They used x-ray fluorescence to determine the composition and thickness of each layer in nine faces painted by Leonardo over 40 years. The scientists also found different recipes used by Leonardo to create the shadows on the faces. These recipes are characterized by a technique (the use of glaze layers or a very thin paint) and by the nature of the pigments or additives. In the case of the glazes, layers of 1 to 2 μm were applied to obtain a total thickness of no more than 30 to 40 μm. The results obtained in this study help to understand Leonardo's search toward making his art look alive. For more information, visit: www.esrf.fr