Integrated analytical approach to unveil the secrets of the recently discovered “Sphinx Room”: a new piece of Domus Aurea puzzle

The recent discovery of the Sphinx Room, belonging to the Domus Aurea Esquiline wing, thanks to the framework given by the project “Non-destructive analytical studies at Parco Archeologico del Colosseo (Rome, Italy)”, allowed to perform an analytical campaign, both in situ and on micro-fragments. The first aim was to contribute to the overall comprehension of the Domus Aurea complex and to contextualize the newly-discovered room inside this extraordinary imperial architecture by means of an archaeometrical characterisation of the painting materials. The palette, composed of Egyptian blue, green earths, iron- and lead-based red, orange and yellow, calcite, carbon-based black, allowed to compare the Sphinx Room to Corridor 92 and Room 114 of Domus Aurea and to other sites in Rome. Furthermore, the employ of an organic binder in some spots can be put forward based on spectroscopic results, which does not exclude a wider use of the a fresco. Furthermore, a complementary methodological strategy was designed, in order to achieve a complete characterization of the materials. In addition to the well-known combination of portable X-ray fluorescence and portable/laboratory Raman analyses, Infrared Fourier Transform Spectroscopy was used, both in situ (Diffuse Reflectance) and in the lab (Attenuated Total Reflectance). The results confirm the suitability of this approach for the characterization of Roman wall paintings, where both inorganic and organic materials are simultaneously present.