Method for the preparation of a film forming flame retardant comprising nitrogen and silicon in its chemical composition, said method comprising the following steps: i. conversion of Z 1 moles of amine moiety, selected from the group of primary and secondary amine and covalently bound to Z 2 moles of one or more at least partially hydrolysable silane moiety, with Z 3 moles of a chemical substance selected from a group of chemical substances obtainable from carboxylic acids or carbonic acid and represented by formula, or wherein Z 1 is a number >0 Z 2 is a number >0 Z 1 / Z 2 ≥ 1 Z 3 is an number >0 Z 1 > Z 3 R 1, R 2, R 3, R 4 are independently from one another selected from a group of chemical functional groups of low polarity consisting of hydrogen, saturated C 1 -C 24 alkyl, unsaturated C 1 -C 24 alkyl, N-alkyl, C 1 -C 12 alkylphenyl, aryl with 6 to 20 ring atoms, heterocyclyl with 5 to 20 ring atoms, all of these optionally substituted by moieties selected from a group of chemical moieties of high polarity consisting of hydroxy, alkoxy, cyano and carbamoyl moieties, X 1, X 2 and X 3 are independently from one another selected from a group consisting of O, S and NH; ii. conversion with at least one HO-functionalized substance of formula M x y R 5 z wherein M is selected from the group consisting of Al, Si, Ti, Fe, Cu, Zn, x, z are integer numbers in the range from 0 to 8, y is an integer number in the range from 1 to 8 x + z > 0 and R 5 is selected from a group consisting of H, saturated C 1 -C 24 alkyl, unsaturated C 1 -C 24 alkyl, and C 1 -C 12 alkylphenyl, while the chemical substance of formula, or is selected from a group consisting of 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 2-hydroxynaphtoic acid, 3-hydroxynaphtoic acid, 4-hydroxynaphtoic acid, 6-hydroxynaphtoic acid and esters or amides thereof, 2-hydroxybenzonitrile, 3-hydroxybenzonitrile, 4-hydroxybenzonitrile, 2-hydroxynaphtonitrile, 3-hydroxynaphtonitrile, 4- hydroxynaphtonitrile, hydroxynaphtonitrile. i. conversion of Z 1 moles of amine moiety, selected from the group of primary and secondary amine and covalently bound to Z 2 moles of one or more at least partially hydrolysable silane moiety, with Z 3 moles of a chemical substance selected from a group of chemical substances obtainable from carboxylic acids or carbonic acid and represented by formula, or wherein Z 1 is a number >0 Z 2 is a number >0 Z 1 / Z 2 ≥ 1 Z 3 is an number >0 Z 1 > Z 3 R 1, R 2, R 3, R 4 are independently from one another selected from a group of chemical functional groups of low polarity consisting of hydrogen, saturated C 1 -C 24 alkyl, unsaturated C 1 -C 24 alkyl, N-alkyl, C 1 -C 12 alkylphenyl, aryl with 6 to 20 ring atoms, heterocyclyl with 5 to 20 ring atoms, all of these optionally substituted by moieties selected from a group of chemical moieties of high polarity consisting of hydroxy, alkoxy, cyano and carbamoyl moieties, X 1, X 2 and X 3 are independently from one another selected from a group consisting of O, S and NH; Z 1 is a number >0 Z 2 is a number >0 Z 1 / Z 2 ≥ 1 Z 3 is an number >0 Z 1 > Z 3 R 1, R 2, R 3, R 4 are independently from one another selected from a group of chemical functional groups of low polarity consisting of hydrogen, saturated C 1 -C 24 alkyl, unsaturated C 1 -C 24 alkyl, N-alkyl, C 1 -C 12 alkylphenyl, aryl with 6 to 20 ring atoms, heterocyclyl with 5 to 20 ring atoms, all of these optionally substituted by moieties selected from a group of chemical moieties of high polarity consisting of hydroxy, alkoxy, cyano and carbamoyl moieties, X 1, X 2 and X 3 are independently from one another selected from a group consisting of O, S and NH; ii. conversion with at least one HO-functionalized substance of formula M x y R 5 z wherein M is selected from the group consisting of Al, Si, Ti, Fe, Cu, Zn, x, z are integer numbers in the range from 0 to 8, y is an integer number in the range from 1 to 8 x + z > 0 and R 5 is selected from a group consisting of H, saturated C 1 -C 24 alkyl, unsaturated C 1 -C 24 alkyl, and C 1 -C 12 alkylphenyl, while wherein M is selected from the group consisting of Al, Si, Ti, Fe, Cu, Zn, x, z are integer numbers in the range from 0 to 8, y is an integer number in the range from 1 to 8 x + z > 0 and R 5 is selected from a group consisting of H, saturated C 1 -C 24 alkyl, unsaturated C 1 -C 24 alkyl, and C 1 -C 12 alkylphenyl, while