Abstract: A fast-curing hybrid binder is disclosed which is suitable for use in refractory molds, which has the advantage of a reduced organic-solvent content. The binder contains two silica sources: colloidal silica and a prehydrolyzed organosilicate in the form of a mixture of an alkylpolysilicate and an alkyl or aryl alkoxy silane, preferably selected from the group consisting of C.sub.1 to C.sub.6 alkyl trialkoxy silanes, di (C.sub.1 to C.sub.6) alkyl dialkoxy silanes, phenyl trialkoxy silane, diphenyl dialkoxy silane, and mixtures thereof. Preferably, the alkylpolysilicate is prehydrolyzed tetraethyl orthosilicate and the alkoxy silane is methyl triethoxy silane, dimethyl diethoxy silane or a mixture thereof.

Abstract: A method for preparing a hybrid binding liquid comprises coloidal silica derived from the hydrolysis of an alkyl silicate and from an acidic organo-aqueous silica sol. More than 50% by weight of silica is derived from the sol by the expedient of replacing part of the water in a commercially available silica sol either by a polyhydric alcohol or by silica.