Traditional western techniques for gilding of polychromed sculptures and panel paintings include the use of grounds prepared by the application of a first layer of gesso grosso followed by a gesso sottile layer, as described by Cennino Cennini in his treatise on painting techniques. These techniques were used in Italy since the middle ages, and were later adopted by many artists in the new world in the regions under Spanish and Portuguese (Brazil) rule, sometimes with local variations in materials and techniques.

This paper discuss the use of FT-IR spectrometry for the identification of inorganic materials present in the grounds of baroque wooden polychromed sculptures from Minas Gerais, Brazil. This technique allows the quantitative analysis of the separate layers of the grounds, with respect to the anhydrite/gypsum ratio present in the sample. The technique has several advantages over the one currently used (Debye-Scherrer chamber for powder X-Ray diffraction). FT-IR spectra can be obtained in a few minutes allowing quantitative results, while XRD usually takes more time and does not give accurate data for quantitative studies. The paper also discusses the results of the studies of the grounds in Brazilian polychromed sculptures and compares the original Italian technique with Portuguese and Spanish techniques and its variations in Brazil.