Leonardo's Donna Nuda unveiled

The painting "Donna Nuda" by Leonardo was acquired by Catherine II (the Great) from the R. Walpole collection, Houghton Hall, England, in 1779 for the Hermitage in St. Petersburg. By exploiting the EVA film technology (ethylene vinyl acetate polymer embedded with strong cation and anion exchangers and with C₈ and/or C₁₈ resins) we have explored the surface of the painting in order to ascertain the techniques used in its drawing. Five EVA films were affixed on the body and on the landscape for 60 min. Upon elution from the recovered films, the harvested material was analyzed by gas-chromatography/mass spectrometry as well as by liquid chromatography/mass spectrometry. "Tempera grassa" (consisting of linseed oil admixed with egg yolk) was used in the entire painting. The surface was then protected by a layer of conifer resin. It is hypothesized that access to the layer underneath the protective layer was obtained via micro-cracks on the conifer resin itself. Rosemary oil was used as diluent to slow down the drying process and so to perform the glazing technique, thus obtaining the "aerial perspective" in correspondence of the landscape. To our reckoning, this is the first time in which a Leonardo painting is analyzed in depth but also in which his artistic technique is deciphered via modern techniques for exploring Cultural Heritage. The EVA film technology might be used for ascertaining the authenticity of paintings and uncover frauds. SIGNIFICANCE STATEMENT: Leonardo da Vinci was the most famous Italian polymath of the Renaissance and one of the most important innovators of his time. He was the author of several important artworks such as "La Gioconda", but he also painted the "Donna Nuda" conserved at the Hermitage Museum. Although some attempts permitted the identification of part of the materials used by Leonardo, to date no analytical investigations were able to fully characterize and decipher the recipes. We explored the surface of the "Donna Nuda" painting through a non-invasive approach that uses a functionalized film to adsorb nano-scopic amounts of materials that were then analyzed by mass spectrometry. This method has the potential to revolutionize the approaches used to analyze cultural heritage.