Analytical chemistry approach in cultural heritage: the case of Vincenzo Pasqualoni's wall paintings in S. Nicola in Carcere (Rome)

An analytical approach applied to Vincenzo Pasqualoni's wall paintings in the apse of S. Nicola in Carcere (Rome) is described in this work. The diagnostic campaign was guided following the indications of the restorers, which were supported over all the phases of the restoration, addressing the multi-analytical approach to identify the original pigments palette used by artist, the conservation state and the presence of consolidants materials, by using spectroscopic techniques supported by chemometric analyses. In particular, reflectance spectroscopy from ultraviolet to short wavelength infrared (UV-VIS-SWIR) combined with chemometric approach, X-Ray Fluorescence spectroscopy (XRF) and Raman spectroscopy are used to characterize the original pigments palette and execution techniques. In addition, original binders and synthetic compounds, used in previous restoration treatments, were detected by using Time Gated Laser Induced Fluorescence spectroscopy (TG-LIF) and Fourier Transform Infrared (FT-IR) spectroscopy. The obtained results onto the case study of S. Nicola in Carcere is a proof of a synergic integration between scientific analytical methods and conservation/restoration approach, subject of high impact and interest in the field of Cultural Heritage. Specifically, through the application of the above-mentioned techniques it was possible to identify the palette used by the artist, mainly composed of inorganic pigments such as ochers, chrome green, cobalt blue, and others. About the binders used by the artist we deduce the use of fresco technique for the upper part of the apse, combined with the use of tempera for retouches. Finally, the presence of acrylic-based compounds used in previous restoration treatments was also documented.