Case study: Field and in-situ identification of pigments in works of art by micro-Raman and visible-NIR reflectance spectroscopies: a polychrome 16th-century Italian fresco and black-coloured Etruscan pottery

A portable micro-Raman spectrometer was developed and tested for field analysis of a 16th century Italian fresco. Despite the fluorescence background in the studied area of the fresco, one or more peaks were recorded with a signal-to-noise ratio sufficiently high to allow the identification of the pigments. On the same fresco, measurements were also carried out using fiber optic visible NIR reflectance spectrometer, which demonstrate that this technique complements Raman spectroscopy as far as the field identification of pure pigments is involved. However, it should be emphasized that Raman spectroscopy is in fact the only technique that can supply positive evidence in the field for a carbon-based pigment. In addition, the study of black colored Etruscan pottery also showed that micro-Raman and visible NIR reflectance spectroscopy are complementary techniques that provide for a sound in situ elucidation of the chemical composition.