Original mortars and plasters represent an important source of historic information, which frequently is insufficiently utilized. The injection grouts used for stabilizing ancient masonry are too often prepared without any theoretical knowledge of what qualities the materials being injected should have. Mortars with low porosity and excessive mechanical resistance often come into contact with ancient structures, or are used next to major works of art. Twenty-six reports focused upon such topics. See 19-1792. -- AATA