In an attempt to evaluate their effectiveness, tests were performed on samples of Briar-Hill sandstone and Indiana limestone which had been treated with commercial stone consolidants. Of the 25 products treated (silicones, fluoridated organic compounds, epoxies, polyurethane, butyl acrylate, acrylic ester, methyl acrylate, silanes), ten failed to produce reconstituted specimens and ten produced specimens with very low tensile strengths. The four most successful consolidants were tested for increase in compressive strength on limestone with successfulresults. Eleven consolidants were tested for depth of penetration of sandstone with mixed results. Eighteen consolidants darkened the sandstone in varying amounts. Only one consolidant, epoxy, improved the acid precipitation resistance of limestone to any considerabel extent. All consolidants tested reduced the thermal expansion of sandstone, but only a few reduced the thermal expansion of limestone. See also 21-900 for related study and 21-1334 for entire proceedings. -- AATA