The effect of organosilanes on deteriorated limestone has been investigated. Particular attention was paid to the depth of penetration, effects on color and degree of consolidation. Three systems, a solution of acrylic silane in methyltrimethoxy silane, Wacker H and Wacker OH were found to be the most suitable consolidants for use on limestones. The first treatment of stone containing soluble salts was investigated. It was shown that organosilanes do not encapsulate salt in stone and that soluble salts can be removed by a poulticing technique following consolidation. -- AATA