History and Techniques of a Polychrome Wooden Statue, How an Integrated Approach Contributes to Resolving Iconographic Inconsistencies

Abstract

The object of this paper is the diagnostic campaign performed on the polychrome wooden statue, revered as St. John, stored in the church dedicated to the “Beata Vergine d’Itria” (Blessed Virgin of Itria), (Noragugume town, Sardinia, Italy). The restoration of the statue gave the occasion to investigate micro-samples from the wooden support and from the polychromy in order to gather information that could be useful for the intervention. In fact, there was limited information on this fine carved statue and its iconographic pattern appeared to be not strictly canonical. Moreover, these kinds of artworks, having religious significant for the faithful, have been generally modified over time to satisfy possible changes in artistic or religious needs or ecclesiastical reforms. The aims of this study are: (i) support the restorers in defining the conservation status of the statue, and (ii) perform a series of analyses to identify the wood and the materials of the painting layers. Specifically, wood micro-sample was examined under the microscope in order to investigate the anatomical characteristics useful to identify the species; pigments were studied through X-ray fluorescence spectroscopy (XRF) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS); organic materials were analysed by Fourier transform infrared spectroscopy (FTIR); and, lastly, the panting technique was investigated through micro-stratigraphy (MS). The analysis performed on the micro-sample taken from the support allowed for identifying the wood as poplar. XRF detected chemical elements that could be associated to pigments such as azurite, blue smalt, red lead, white lead and ochres, and Au for the gilding. SEM-EDS confirmed these pigments and allowed to find also other elements useful to suggest the presence of further materials such as Ag in the metal foil. FTIR detected proteinaceous binder and siccative oils that were mapped in the micro-stratigraphy by using histochemical tests. All this information was used by the restorers to address the intervention from the cleaning to the final retouching.