Ancient surface treatments of the historical architecture: methodological data comparison from different study cases

The work focuses on a comparison of petrographic-compositional data between the treatments of some ancient monuments of Tuscany and Sardinia. The purpose is to analyse the differences of surface finishes of various stones and bricks. In fact, the surface finishes can have an original aesthetical and protective function, but they can represent also subsequent treatments to adapt the surface to the color of the surrounding areas after substitutions or other local interventions. Therefore, it is important to know the type of surface treatment not only for historical-cultural reasons but also to make a more suitable choice of the possibility of remove it. In the surface samples of Tuscany (i.e., Siena Cathedral and Town Hall) and Sardinia (i.e., S. Antioco of Bisarcio and San Geminiano churches) the petrographic analysis, together XRD analyses, of the microsamples revealed the presence of Ca-oxalate which may have originated from organic substances used as binder or finishing.