Diagnostics on Scagliola Altar Frontals from the Area of Modena (Italy)

Traditionally, the town of Carpi is considered the home of scagliola. The old attestations of scagliola masters starting from the 16th century and the presence on the spot of hundreds of altar frontals and other lithurgical and domestic objects testify this tradition, besides the presence of a Municipal Museum of Scagliola in the Castle of Pio family. The art of scagliola developed from the simple white-and-black artifacts to the polychrome altar frontals and tables whit elaborate workmanship, and spread beyond the Modena area, as it is testified by both the works in adjacet provinces and regions, and the propagation of schools whit the transfer of masters outside the Emilia region. Recent studies carryed out by means of non destructive techniques have put in evidence the correspondences among the techniques identified for the preparation of the artifacts and the literature sources. Some more manuscripts preserved in the Archivio Storico of Carpi and amounting to the age of the ruling by the Pio family, indicate a series of materials for preparing the support and the coloured dough. We report the results of a research carried out by means of different analytical methods for the identification of the materials employed in the execution of these artefacts. The research was carried out in order to identify some more correspondences between measurements and old sources and to ascertain possible differences among ateliers or schools. Whereas Raman microscopy enabled to find out the pigments and dyes used for the scagliola, Gas-Chromatografy coupled whit Mass Spectrometry gave micro-distructively information on the nature of binders and of the products for the surface finish. The application of these techniques to the study of some altar frontal samples from the area of Carpi, Modena and Reggio has led to the identification of pigments such as minium, vermillon, lazurite, orpiment, red and yellow ochres, lead white and lampblack, and of dyes such as indigo, saffron, and of a red dye with a clear spectrum, but unknown nature. The binder corresponds to an animal glue that is locally known as “colla garavella” or “german glue”, the preparation of which is reported in many medieval and Renaissance recipe-books.