Saint Petronio Basilica in Bologna (Italy): a case study on a XVI C. mural painting

During the last restoration (2006) of mural paintings by Girolamo da Treviso in Saint Petronio Basilica in Bologna (Italy), scientific investigations were carried out to acquire detailed information about the painting technique and the degradation products. The identification of materials allowed a correct restoration. Fourteen micro samples were collected in different areas selected by the restorer who identified the original partszones of the work painting. The study was based on analysis of fragments and cross-sections, that were prepared to acquire stratigraphic informations. The following techniques were used to investigate inorganic and organic materials: stereo microscopy in visible and UV light, X-ray powder diffraction (XRD), Raman micro-spectroscopy, Fourier Transformed Infrared micro-spectroscopy (μ-FTIR) used in Attenuated Total Reflection (ATR), Scanning Electron Microscope coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDS) and Gas Chromatography coupled with Mass Spectrometry (GC-MS). Few pigments were identified, all very traditional, and a clear presence of organic binding media was detected. This study emphasizes that the paint technique is not a typical “buon fresco”. Probably the pictorial technique itself, used in this cycle, together with environmental conditions, caused the darkening of some white areas. A diffuse presence of gypsum was also detected in some degraded painting portion