Multi-Technique Approach by Traditional and Innovative Methodologies to Support the Restoration of a Wall Painting from the 16th Century at Palazzo Gallo in Bagnaia, Viterbo, Central Italy

This paper summarizes the main results of the study, diagnostics, and restorations conducted and applied to a 16th century wall painting (a portion of the frieze and the Riario coat of arm) in Palazzo Gallo (Bagnaia, Viterbo district—central Italy) recently concluded, which was also the subject of a master’s degree thesis in Conservation and Restoration of Cultural Heritage at the University of Tuscia, Viterbo. Innovative imaging techniques were used for the first time on a wall painting on-site: hypercolorimetric multispectral imaging (HMI) and pulse-compression thermography (PuCT), combined with more traditional analysis such as X-ray fluorescence spectroscopy, Fourier transform infrared spectroscopy, and cross-section investigation. HMI allowed for mapping the conservation status before and after the removal of the scialbo layer that covered the original paintings. It also allowed different areas of the painting to be compared and for verifying the effectiveness of the cleaning. PuCT enabled the detection of cracks and discontinuities in the ground layers and to evaluate the depth of such anomalies, giving valuable support in the consolidation step. Moreover, passive thermography was used to monitor the penetration level of a hydraulic mortar in real time, a technique that was greatly helpful for verifying the successful fill and consolidation of voids beneath the pictorial layer. Overall, the multi-technique approach reported here was of considerable assistance for restoration of the mentioned artwork, the result of which has also been documented.