Analysis of a Brazilian baroque sculpture using Raman spectroscopy and FT-IR

Spectrochim Acta A Mol Biomol Spectrosc. 2016 Feb 5:154:67-71. doi: 10.1016/j.saa.2015.10.013. Epub 2015 Oct 21.

Abstract

In this study, samples were taken from the sculpture of Our Lady of Sorrows and analyzed by Raman spectroscopy and FT-IR. This sculpture has been dated to the early eighteenth century. Samples were also examined using optical microscopy and Energy Dispersive Spectroscopy (EDS). Based on chemical analysis, the pigments vermilion [HgS], massicot [PbO] and azurite [Cu3(CO3)2(OH)2]were found in the sculpture polychrome. The results indicate that the green polychrome of the sculpture's mantle comes from the blending of massicot and azurite. Because the literature reports that the mantle of the Our Lady of Sorrows sculpture is blue, the mixing of these pigments results from a production error. The results also indicate the presence of Au in the sculpture, which indicates the originality of the piece. The results from this study helped restorers to choose the appropriate procedures for intervening in the sculpture and contributed to the knowledge about the manufacturing process of Brazilian baroque sculptures.

Keywords: FT-IR; Pigments; Polychrome baroque sculpture; Raman spectroscopy.