Mural paintings of the cubicle "dei fornai" in Domitilla catacombs in Rome: a study via non-invasive techniques

At the first level of Domitilla catacombs in Rome, in a peripheral region dating back to the mid-fourth century, is located the cubicle known as "dei fornai" (of the bakers). The cubicle presents some stylistic inconsistencies: subjects and themes suggest the attribution to a customer belonging to the upper class and having an important status, while some parts were made hastily and not well finished. In order to better shine a light on this matter, a diagnostic campaign was carried out, exclusively by means of in situ non-invasive methods and techniques. All the data reported in this work were collected after a laser cleaning of the wall paintings: some fibre optics reflectance spectroscopy (FORS) measurements were made before the cleaning but the poor data obtained are not here reported. After the laser cleaning, a combination of non-invasive techniques was employed in order to univocally identify pigments and materials. Colorimetry, fibre optics reflectance spectroscopy (FORS), infrared spectroscopy in external reflection mode (ER FT-IR), X-ray fluorescence spectrometry (XRF), digital microscopy (DM) and visible-induced luminescence (VIL) were therefore utilised in situ, and brought to unambiguously assign the colour palette.