A binder is described which comprises A) a hydrolysate or heterocondensate of at least one hydrolysable silicon compound and at least one metal, phosphorus or boron compound, the metal being selected from Al, Ge, Sn, Pb, Ti, Mg, Li, V, Nb, Ta, Zr and Hf, B) an organic polymerizable or polycondensable monomer or oligomer and C) a buffer, so that the pH of the buffered binder is in the range from 2 to 7, and optionally a complexing agent, if appropriate, the at least one hydrolysable silicon compound comprising one or more hydrolysable silicon compounds having at least one nonhydrolysable group or oligomers thereof. The binder is suitable for consolidating bulk or loose substrates.