S741 is a special product for reinforcing and strengthening crumbled and weathered stone. It can be used on absorbent sandstone, mortar joints and plastering. Surfaces treated with S741 remain vapour permeable and UV resistant. Not effective on marble and most limestone because they are not absorbent enough. After treatment is completed apply HMK S731 Silane Impregnator to the treated area to reduce the penetration of water and dirt.