A multi-analytical diagnostic approach for the characterization of heavily repainted wooden sculptures dated to the fifteenth century

The polychrome wooden sculpture is a complex artifact because of the presence of different materials and techniques. Due to changes in style, objects closely related to the cult were often over painted. The present study aim to identify and set-up a correct investigation methodology to identify pigments and binders of the original layer and subsequent overpaintings that often characterize polychrome wooden sculptures, pointing out how the acquisition of these data can be a support not only to the activity of the restorer, who frequently has to face the removal of the overlayers, but also to the deepening of the historical artistic context, connected to the knowledge of the work of art. In this study a multi-analytical approach has been applied on two fifteenth-century Ligurian Christs, the first one from San Bartolomeo parish in Zuccarello, the second from Borghetto San Nicolò, both heavily repainted. The application of different analytical techniques is in fact often successfully for paints analysis [1]. By comparing the results of XRF analysis performed with portable instrumentation on stratigraphic sequences related to samples coming from different color areas of the work, with the data obtained by SEM-EDS, the inert of the different layers could be identified, then confirmed by μ-FTIR that also revealed the chemical nature of the binders employed confirmed and identified by GC-MS analysis [2]. At this purpose both standards and mock up samples prepared following the ancient recipes were analyzed following the conventional approach based on GC-MS analysis and a new methodology based on nLC-MS/MS analysis to characterize in one single shot the protein content. The samples were digested by endoproteases, such as trypsin, and directly analysed by high resolution mass spectrometry. The use of bioinformatic tools resulted in the identification of proteins. The same approach will be used to analyse the real samples [3]. The complete samples analytical characterization has allowed a new possibility of comparison for the classification system of the " selva dei Cristi feriti liguri quattrocenteschi nel Ponente", to which the two statues belong, proposed in the text "La Sacra Selva. Scultura lignea in Liguria tra XII e XVI secolo " [4]. References [1] Fermo, P., Piazzalunga, A., De Vos, M., Andreoli, M. Applied Physics A: Materials Science and Processing, 2013, 113, 1109-1119.