Abstract: A process is described for the production of condensation products which be converted into glass, in which at least one silicon compound which can be hydrolyzed to form SiO.sub.2, at least one compound which can be hydrolyzed to form Al.sub.2 O.sub.3, B.sub.2 O.sub.3 or TiO.sub.2 and at least one hydrolyzable alkali metal compound or alkaline earth metal compound is brought into contact with at least the stoichiometrically necessary amount of water. The hydrolysis is carried out according to the invention in the presence of a complexing agent selected from the group consisting of .beta.-carbonyl carboxylic esters and C.sub.2 to C.sub.5 carboxylic acids and their carboxylate ions, which prevents precipitates of hydrolysis products of the very reactive aluminum and boron compounds forming while the less reactive silicon compounds remain unchanged or are only partially hydrolyzed.