Classification of Multi-layered plaster in St. Abbondio Cloister at Como, Italy: an anlytical tool for architectural archaeology

St. Abbondio (Como, Italy) is one of the most outstanding Romanesque Basilicas of Northern Italy. The entire building, and particularly the Cloister, has undergone various interventions during the last centuries, until the last conservation work occurred in between 2000 and 2003. On this occasion a deep analytical investigation has been performed on internal and external plasters, in order to classify them by the compositional and morphological point of view and to enlighten the conservation history of the Cloister. Plasters representative of the different building phases were characterised by X Ray Diffraction of Powders, Porosimetric Analysis, Thin Sections Observations and Atomic Spectroscopy. The results allowed to group samples with similar properties, corroborating the historic hypotheses about the sequence of the building interventions and suggesting an analytical procedure, which could be used as a valid tool in case of archaeological building investigations.