Abstract: The present invention relates to a method for preparing a surface for bonding with a synthetic resin. In the method, a layer is applied onto a substrate surface by sand blasting with a composition comprising (A) 0.01 to 90% by weight of an optionally silanized material having a particle size less than 5 .mu.m and having a hardness greater than that of the substrate surface, and/or (B) 20 to 100% by weight of a silanized siliceous material having an average particle size of 2 to 200 .mu.m, and (C) the remainder of the sand blasting composition having an average particle size greater than 5 .mu.m, and optionally the layer is thereafter silanized. The invention is further directed to the above-mentioned composition.