A method of treating keratinous material, in particular human hair, comprising applying to the keratinous material - a first composition comprising: at least one organic C 1 -C 6 alkoxy silane selected from the group consisting of (3-aminopropyltriethoxysilane, (3-aminopropyl)trimethoxysilane, (2-aminoethyl)triethoxysilane, (2-aminoethyltrimethoxysilane, (3-dimethylaminopropyl)-triethoxysilane, (3-dimethylaminopropyltrimethoxysilane, (2-dimethylaminoethyl)-triethoxy-silane, (2-dimethylaminoethyl)trimethoxysilane and/or condensation products thereof, and at least one organic C 1 -C 6 alkoxysilane selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane and/or condensation products thereof, - a second composition which has a pH of from 8.0 to 10.5 and which contains at least one compound selected from the group consisting of amino acids and protein hydrolysates, wherein - the total content of all polymers contained in the composition - based on the total weight of the composition - is below 0.1% by weight, and - the total content of all polymers contained in the composition - based on the total weight of the composition - is below 0.1% by weight. - a first composition comprising: at least one organic C 1 -C 6 alkoxy silane selected from the group consisting of (3-aminopropyltriethoxysilane, (3-aminopropyl)trimethoxysilane, (2-aminoethyl)triethoxysilane, (2-aminoethyltrimethoxysilane, (3-dimethylaminopropyl)-triethoxysilane, (3-dimethylaminopropyltrimethoxysilane, (2-dimethylaminoethyl)-triethoxy-silane, (2-dimethylaminoethyl)trimethoxysilane and/or condensation products thereof, and at least one organic C 1 -C 6 alkoxysilane selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane and/or condensation products thereof, at least one organic C 1 -C 6 alkoxy silane selected from the group consisting of (3-aminopropyltriethoxysilane, (3-aminopropyl)trimethoxysilane, (2-aminoethyl)triethoxysilane, (2-aminoethyltrimethoxysilane, (3-dimethylaminopropyl)-triethoxysilane, (3-dimethylaminopropyltrimethoxysilane, (2-dimethylaminoethyl)-triethoxy-silane, (2-dimethylaminoethyl)trimethoxysilane and/or condensation products thereof, and at least one organic C 1 -C 6 alkoxysilane selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane and/or condensation products thereof, - a second composition which has a pH of from 8.0 to 10.5 and which contains at least one compound selected from the group consisting of amino acids and protein hydrolysates, wherein - the total content of all polymers contained in the composition - based on the total weight of the composition - is below 0.1% by weight, and - the total content of all polymers contained in the composition - based on the total weight of the composition - is below 0.1% by weight.