In situ macroX-Rayfluorescence scanning on a Leonardo da Vinci portrait

Recently, an oil-on-panel painting, portraying Leonardo da Vinci, was found in the monastery of Camaldoli (Arezzo, Italy). The painting comes from a private donation and, over time, it never was moved from the monastery or loaned to museums or art galleries for exhibitions. Historians hypothesise that the painting could be a seventeenth-century copy of a portrait or a self-portrait of Leonardo da Vinci. Although, almost certainly, the panel was not signed by Leonardo, it raised a great interest for art experts, since the copy could be the outstanding testimony left to us of an original Leonardo's masterpiece, which is gone lost. The ICRCPAL in Rome, in collaboration with the ISPC-CNR and the INFN-LNS of Catania, started a scientific investigation of the painting based on the use of non-invasive techniques. Macro X-ray fluorescence imaging technique (MA-XRF) was employed to document, for the first time, the nature of original pigments composing the pictorial and priming layers. The results allowed to better elucidate the painting technique, also to know the original look of degraded areas, suggesting an appropriate restoration and conservation policy. Novel information has been obtained concerning the pictorial process, since elemental distribution maps revealed an underpainting below the Leonardo portrait. Despite the cleaning process of the panel before its reuse, some pictorial details remained visible to the MA-XRF analysis, allowing to infer the presumed figure hidden behind the figure of Leonardo.