Characterization and Analysis of Gypsum Alabaster Constituting the “Santissimo Salvatore” Statue by Gabriele Brunelli (Bologna, 1615–1682)

This study is part of a broader conservation and restoration project of the 17th-century statue "Santissimo Salvatore" attributed to the Bolognese sculptor Gabriele Brunelli (1615-1682). This sculpture was traditionally classified as a marble statue, i.e., primarily composed of calcium carbonate. However, the careful diagnostic analyses conducted during the present work of restoration revealed that, instead, the sculpture is made of gypsum alabaster, a material predominantly composed of calcium sulphate hydrate (CaSO42H2O). In the present research, a multi-analytical investigation was carried out using X-Ray Powder Diffraction (XRPD), Field Emission Environmental Scanning Electron Microscopy (FE-ESEM) with Energy-Dispersive X-ray Spectroscopy (EDS), and confocal Raman microspectrometry. Here, we report detailed and updated analytical data of the material constituting the "Santissimo Salvatore" statue by Gabriele Brunelli. These data were found extremely useful to plan and accomplish the restoration work in detail: (i) the suitable conservation project of the artwork, (ii) the reassessment of the knowledge on the artist's sculptural production, and (iii) gaining more information about the material used in the 17th-century Bolognese sculptural context.