The consolidation of stone materials by impregnation with pure monomers and subsequent polymerization has certain advantages. Due to a low viscosity of about 0.6cP the monomers will reach the inner parts of the stone very rapidly, where they will solidify. Pieces of sandstone weighing about 100g, which had a porosity of 19% and a specific weight of 2.1, were impregnated in a bath for ten minutes with a solution of 2% benzoyl peroxide and 0.6% dimethyl paratoluidine in methyl methacrylate. In the first case a piece of sandstone was wrapped in aluminum foil to prevent evaporation. In the second case the impregnated sandstone was kept in the monomer solution for an additional two hours, wiped dry, and aired at room temperature without further prevention of evaporation. In the third method, the impregnated piece was removed from the solution after ten minutes and allowed to cure at room temperature without prevention of evaporation at all. After two days the pieces were weighed 4% again after vacuum-drying at 30°C for about five hours, and the polymer content was determined. The percentage retention was defined as the ratio of the polymer weight to the amount originally introduced. With the first impregnation method the retention varied from 50-75%, in the second from 86-90%, and in the third about 40%. Reversibility is all additional advantage of this method in contrast to impregnation with epoxy resins or to the silicone-estersandstone consolidator.