Leonardo under cover: A Raman spectroscopy investigation of a historic painting

The study of artwork is an interesting field that has undergone a major turn the last decades as the use of scientific analysis methods have increased and become a significant part of the investigations. In this study we have employed Raman spectroscopy to analyse the pigments in an old canvas painting of the Roman Emperor Domitian. The painting is of special interest since its creation is historically attributed to Tiziano Vecellio, more known as Titian, but it has recently been found to contain a signature that reads L daVinci. We here perform a rigorous pigment analysis of the painting and signature area to identify and classify the pigments by usage and the potential time of deployment. Microscopic cut outs from selected areas of the painting were analysed in a Raman microscope where 13 different pigments were identified: azurite, carbon black, chalk, cinnabar, gypsum, lead tin yellow type 1, lead white, massicot, Prussian blue, red ochre, titanium white, ultramarine and yellow ochre. Out of these, 12 pigments were contemporary with Titian (1488/90-1567) and Leonardo da Vinci (1452-1519), one pigment, titanium white, was present during the Roman period but came into common use at a later time and one pigment, Prussian blue, is of newer origin. Complimentary X-ray imaging shows that at least one of the areas where Prussian blue was found has likely been altered at a later stage, providing an explanation for the presence of a modern pigment in an old painting. Special emphasis was also applied to resonant and non-resonant Raman response of Prussian green and blue, expressing different ratios of Fe 2+ and Fe 3+ states, valuable for identification and discrimination of the compounds in pigment identification and in the more recent field of battery research.