Multi-analytical investigation of panel, pigments and varnish of The Martyirdom of St. Catherine by Gaudenzio Ferrari (16th century)

The recent conservative project of the imposing panel painting The Martyrdom of St. Catherine painted by Gaudenzio Ferrari (c.1477–1546) has been a precious opportunity to deepen the scientific knowledge about the execution technique—hitherto scarcely investigated—of one of the prominent exponents of the Lombard and Piemontese Renaissance. The conservative intervention had become necessary because of serious problems of the wooden support: cracks and deformations had caused lifts and color gaps. In addition, over time, many overpaints and varnishes had been altered, obscuring the brilliant original color tones of the painting. A diagnostic survey was planned based on a multidisciplinary approach consisting of a well-established protocol of non-invasive imaging (UVF, IRR, IRFC, RX) and point techniques (XRF, Vis-NIR FORS). The diagnostic analyses were performed in situ and carried out in the restoration laboratory of the Pinacoteca di Brera, an ad hoc space that allows visitors to see in real time restorers and scientists at work during the different stages of the conservation treatments. Analyses on micro-samples were further performed in laboratory by means of FTIR, Raman, SEM-EDX and GC-MS techniques. The research group together with restorers and art historians were able to deepen the understanding of the artwork from a technical, material and conservative point of view, making it possible a specific conservative intervention. Furthermore, the results of this research allowed shedding light on the mounting system of the wooden support and on the reconstruction of the original color palette used by the artist. An interesting point was the presence of pararealgar as an intentional use or as a result of the realgar alteration in some yellow areas. The huge dimensions of the painting (331 × 210 cm) forced the researchers to find unconventional technical solutions for a complete overview of the conservative condition. The results obtained from the precise recognition of the state of preservation of the varnish, the painting layers, the preparatory layers and the wooden support are here presented.