The present invention relates to a process for performing a controlled hydrolysis and condensation of an epoxy-functional silane of the general formula I R1-SiR′m(OR)3-m (I) in which R1 is a (III) or (IV) group and R, R′ and R″ groups are the same or different and are each hydrogen (H) or a linear, branched or cyclic, optionally substituted alkyl group having from 1 to 6 carbon atoms, A and A′ groups are the same or different and are each a bivalent alkyl group having from 1 to 10 carbon atoms, R2 groups are the same or different and R2 is a linear, branched or cyclic, optionally substituted alkyl group having from 1 to 20 carbon atoms, and m is 0 or 1, and optionally of at least one further organofunctional silane of the general formula II R2-SiR′n(OR)3-n (II) in which R2 is an organofunctional group as already defined above, R′ is methyl, R groups are each independently hydrogen or a linear, branched or cyclic alkyl group having from 1 to 6 carbon atoms and n is 0 or 1, where from 0.001 to ≦5 mol of water is used per mole of alkoxy function of the silanes used, no further hydrolysis or condensation catalyst is used apart from boric acid as the hydrolysis catalyst and condensation component, and the condensates formed in the reaction are based on Si—O—B— and/or Si—O—Si bonds.