A process for preparing a binder which comprises a heterocondensate of silicon compounds and metal and/or boron compounds. The process comprises mixing a silicon component which comprises (A), at least one hydrolyzable silicon compound having a non-hydrolyzable polymerizable group, with water to form a hydrolysis product, and 15 s to 15 min after mixing (A) with water, the addition of (B), at least one compound of boron or a metal selected from Al, Ga, In, Tl, Ge, Ga, Sn, Pb, Ti, Zr, Hf, Sc, Y and La.