The mortars in two groups applied in subsequent periods were differentiated by mineralogical, chemical, and physical analyses. The first group (Group A) mortars have a binder made from animal and vegetable fats and a filler made by litharge and lead metaborate hydrate. The second group (Group B) mortars have an epoxy resin binder. A filler made by sands or powdered stone (marble, Simona sandstone) is present in both groups. Group A refers to the restoration work carried out in the late 19th century and Group B to the work done after World War II.