Multi-analytical study of Roman frescoes from Villa dei Quintili (Rome, Italy)

The present work reports a multi-analytical study, based on Polarized Optical Microscopy (POM), Scanning Electron Microscopy equipped with an Energy Dispersive X-ray detector (SEM-EDX), micro-Raman and Fourier Transform Infrared Spectroscopy (FT-IR) techniques, aimed at establishing the painting techniques and palettes used to decorate a variety of fragments of frescoes coming from Villa dei Quintili in Rome (Italy) and dated back 2nd century CE. This combined methodological approach, covering different spatial scales extending from the macroscopic to the elemental domain, revealed successful for the unambiguous identification and characterization, in non-invasive or at least micro-destructive way, of pigments, binders and stone materials. The used chromatic palette was identified as yellow ochre (goethite), carbon black (vegetal origin), probably green earth and Cu-green pigment, red ochre (haematite), lime white and Egyptian blue (cuprorivaite). Organic and inorganic binders were respectively identified as linseed oil and lime, this latter carbonated to calcium carbonate. Textural features of plasters were also evaluated in order to investigate raw materials used for their production. The obtained data revealed crucial for improving knowledge of materials and preparation methods of pigmenting agents of these fragments, taken from the warehouse of the Villa and hence of unknown provenance area, in view of their right positioning in a specific area of the archaeological complex. In fact, the characterization of the different pigments could support conservators to better identify the distribution of the frescoes among the different rooms, and to reconstruct the original aesthetics of the Villa during the Quintili age.