Study of the degradation causes affecting stucco sculptures from the Valentino Castle in Turin

17th century stuccos located in The Valentino Castle in Turin (Northern Italy) have been studied by means of XRD, TG-DTA, Hg porosimetry and SEM coupled with EDX chemical analysis in order to understand their composition and the degradation causes. The investigated un-degraded samples were made of gypsum, hydrated lime and other carbonates phases on the external surface and up to ca. 20 mm in depth but the compositions were highly heterogeneous. Repeated cycles of water impregnation, coming from roofing infiltration, and evaporation have reached the investigated area and led to severe damages to stuccos due to crystallization of hydrated magnesium sulphate salts.