Characterization of Soluble Salts on the Frescoes by Saturnino Gatti in the Church of San Panfilo in Villagrande di Tornimparte (L’Aquila)

Salt crystallization is one of the most dangerous forms of degradation affecting frescoes. This phenomenon can lead to cracking, flaking and detachment of the pictorial layer, ultimately ruining the work of art. However, the characterization of soluble salts via chemical analysis can be employed to determine the conditions of the artifact and establish the proper restoration and/or conservation strategies to be adopted. In this archaeometric study, a first-ever characterization of the soluble salts and related degradation phenomena on the frescoes by Saturnino Gatti in the church of San Panfilo in Villagrande di Tornimparte (L'Aquila) was carried out. Sampling was performed in areas with evident detachments, exfoliations and saline crystallization (efflorescences). Eleven samples of powder and fragments were taken from different panels of the fresco: nine were taken from Panels A, C, D and E and two from the top part of the vault. Chemical characterizations were performed using two analytical techniques: ion chromatography (IC) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). Ion chromatography was used for the quantification of the main ions and to evaluate the presence of soluble salts, whereas infrared spectroscopy was used to characterize the mineralogical phases. The results show efflorescence consisting of newly formed gypsum and carbonate in samples taken closer to the ground. Furthermore, a good correlation between sodium and chloride ions was observed, indicating the presence of an efflorescence composed of newly formed sodium chloride. Capillary rise and infiltration were highlighted as the main sources of soluble salts. This information will be crucial in guiding future restoration or conservation operations.