Abstract The sample for this study consisted of Indiana limestone and several marble varieties. The treatment varied from surface coatings to in-depth impregnation. The chemical tests included exposure to SO 2 -enriched dynamic atmospheres and immersion in carbonic and sulfurous acid solutions. The SO 2 reactions were studied as a function of the formation of calcium sulfite determined by X-ray diffraction. The acid reactions were studied on leached Ca 2+ determined by EDTA titration and atomic absorption. The physical tests included the soundness test based on hydration of Na 2 SO 4 in the pore space of the stone. Chemically, certain epoxies and silicones increased the reaction relative to controls. The epoxies did so by absorption of gases, the silicones by probably acting as semipermeable membranes. The reactivity of immersed specimens was greater than that of specimens in a gaseous environment. The resin films during 20 to 40 hr of reaction, necessary for steady state, were not discolored or damaged. In soundness tests, in-depth impregnations produced far better results than surface treatments. All silicone treatments highly reduced water and water-vapor absorption but did not proportionally increase the soundness. The soundness was improved in fluorocarbon-acrylic copolymers, but here the chemical improvement was at its best. The maximum improvement of soundness was experienced by epoxy-treated specimens. An absolute prediction of the long-range behavior of preservative treatments in a natural environment seems to be difficult. Above tests only indicate the relative merits and permit identification of materials that may actually accelerate the weathering process.