Hyperspectral imaging and Raman analyses of the red decoration of the St. Mauro altar in St. Salvatore’s Church (Pavia)

In the basilica of St. Salvatore, antependiums belonging to different phases of monument decoration are visible. The most valuable, the marble frontal of the high altar, dates to 1511 and is probably the only one from the first decorative phase of the church. The side altar frontals appear to be made of wood, embroidered damask, or other fabrics. They are partly related to the renovations the basilica underwent when it was reopened for worship in the early 20th century, except for this frontal in St. Mauro’s Chapel, which was plausibly made during the early 18th-century redecoration of the chapel itself. Because of its style and construction, it is assumed to belong to the Baroque decorative phase, referring to the date "1709" painted on the vault. This hypothesis is being verified by means of art-history research supported by the diagnostic study of the materials. The analyses, which are ongoing, were initially conducted on the red areas of the artefact, using portable Raman and visible reflectance spectroscopic techniques. Subsequently, measurements were taken with a hyperspectral camera, obtaining images highlighting the spatial distribution of the red pigments on the frontal.