Mortars and Plasters under the Mosaics and the Wall Paintings of the Roman Villa at Piazza Armerina, Sicily

The Roman Villa at Piazza Armerina in Sicily, built in many successive steps over the 2nd and 3rd centuries A.D., is renowned all over the world for both the wealth and the refinement of its mosaic floors. In February 2007 the Regional Government of Sicily started a restoration project of the whole archaeological site. The systematic survey and study of all decorative elements highlighted the value of wall paintings, which until then were almost unknown except for casual approaches to specific problems of conservation, carried on without any relation to the far and away famous mosaics. This paper shows the results of a physical chemical investigation of the mortars used for both floors and walls, which were extensively sampled both indoor and outdoor, including the crushed brick mortars of the basins at the monumental front entrance of the Villa. The mineralogical petrographic study of mortars and plasters was performed by XR diffractometry and by optical microscopy using polarized light through thin sections. Pigments were analyzed by micro-Raman spectroscopy, simultaneous thermal analysis was also performed in a few cases, in order to further investigate the recipe of the mixture.The results describe the composition of mortar under the mosaics and afford an unpublished view of both materials and techniques used in the wall paintings of the Villa at Piazza Armerina, giving the opportunity for interesting comparison with others archaeological sites under study.