Non-invasive characterization of pigments on "monochromes on marble" from Herculaneum and Pompeii: new researches

This work is a new step in the research about “Monochromes on marbles”, twelve painted marble slabs. Among them, ten are from Pompeii and Herculaneum, and the last two are probably from Rome. The ten slabs from Pompeii and Herculaneum are now preserved in the National Archaeological Museum in Naples and the other two in the Kunsthistorisches Museum in Vienna. These marble pinakes were set in walls of roman buildings with iron clamps, in altars for domestic cults, or probably in gardens of rich private houses. The scenes represent different subjects spanning from mythological to athletic ones. Their name, Monochromes, was chosen in the 18th century due to the red colour visible on the surface, but actually the slabs show also green, yellow, brown and black colours, still visible to the naked eye. The paper presents the results obtained in an in-situ analytical campaign carried out on the ten slabs of the National Archaeological Museum in Naples by using a set of portable, non-invasive techniques. The techniques used can be divided in two groups: 1) special photographic techniques (Ultraviolet reflected photography, Ultraviolet fluorescence photography, Ultraviolet false colour, Near Infrared photography, Infrared false colour, Visible Induced Luminescence) and 2) single spot analysis (X-ray fluorescence spectroscopy, Fiber Optics Reflectance Spectroscopy in VIS). Portable Optical Microscopy was used for the documentation of each single spot analysed. Crossing the results obtained with both imaging techniques and single spot analyses some new information about drawings, pigments and conservation history have been provided, contributing to deepen the knowledge of this rare kind of archaeological objects.