Recovery of a lost wall painting at the Etruscan Tomb of the Blue Demons in Tarquinia (Viterbo, Italy) by multispectral reflectometry and UV fluorescence imaging

This paper presents the results of a multispectral reflectometry and ultraviolet (UV) fluorescence study on the entrance wall of the Tomb of the Blue Demons in the Necropolis of Monterozzi (450-430 bc) in Tarquinia (Viterbo, Italy), which is a UNESCO site. The technique is based on the acquisition of a multispectral set ranging from 10 to 25 images, acquired at wavelengths between 370 and 1120 nm, with a spectral width of 50 nm per image, using both halogen lamps for visible and infrared images and high-purity UV diodes for fluorescence. Blind-source separation algorithms were then applied to the whole image set to extract from the resulting images the details not otherwise visible in the single spectral images. The multispectral technique presented was tested and improved upon over the last decade on ancient Etruscan and Roman wall paintings and, because of its quickness and cost-effectiveness, it can now be proposed as a powerful tool for the study of poorly conserved archaeological wall paintings and a preliminary diagnostic survey before any future conservation intervention on them.