Nondestructive Raman investigation on wall paintings at Sala Vaccarini in Catania (Sicily)

In this work, the results of a Raman campaign for studying seventeenth-century Sicilian frescoes, by using two portable Raman systems, equipped with different excitation sources (785 and 1064 nm), are proposed. The measurements were performed with the aim to provide an in situ diagnostic analysis of the wall paintings (in terms of colorants and preparation layer) and to support the conservators in the framework of the ongoing restoration. The combined use of the two Raman spectrometers has given a complete overview on the artist palette and on the state of preservation of frescoes, also informing us about the technique employed by the painter. Natural pigments as hematite, vermillion, goethite, lead red, lead white and carbon-based black pigments have been identified. Additionally, the application of a transitional Romanesque–Renaissance frescoes method has been noticed by the systematic combined presence of calcite and gypsum in the substrate. Finally, the analyses have highlighted the presence of degradation products, mainly related to alteration of lead-based pigments.