LAUSR

Abstract This paper focuses on the use of gypsum as a binder in stucco artworks made between the 16th and 17th centuries in canton Ticino (Switzerland). As far as the artistic technique is concerned, a stucco statue is made of composite materials: metal, brick or wood for the supporting structure, lime and/or gypsum mortar with aggregate for the ground and finishing layers. The gypsum addition to the lime binder, found mainly in the ground layer, helps accelerate the setting of the three-dimensional stucco elements and prevents cracks from shrinkage, but a real understanding of the technology of its preparation, as well as the proportion of the mix for the stucco production, has yet to be established. The samples of stucco (167) taken from artworks in the region were analysed in stratigraphy, identifying their chemical and mineralogical composition. The results from these investigations were compared with the information provided by the historical sources and archival documents recording the artistic technique. Results showed that the quantity of gypsum varies greatly depending on the requirements of the stucco masters and that it was a fundamental addition to attain the effects desired by the different artists.