Among many hydrophilic high-molecular substances used as a substitute for photographic gelatine, there are some which contain in their molecule free carbonic acid residure, e. g. copolymers of maleic, acrylic or crotonic acid with other vinyl compounds. They react with those substances which have amino and (or) hydroxy groups in their molecule, e.g. gelatine or poly vinyl-alcohol, and as the result they form a net-like structure by their mutual cross-linking, and lose their solubility in water, yet do not lose their swelling property in water or in developer and other processing solutions, in contrast with the behavior of low molecular organic hardening agents, e.g. formaldehyde or mucochloric acid, which highly affect the swelling property as well as the solubility of their host binding agents. We determined melting-points, degrees of swelling and solubilities in water as well as in developer, of the dried gelatine gel films which contain various amounts of those high-molecular hardening agents, i.e. a copolymer of vinyl methyl ether and maleic anhydride (PVM/MA), a copolymer of vinyl acetate and crotonic acid (PVAc/CrA), a copolymer of styrene and maleic anhydride (ST/MA), poly acrylic-acide (PA), or some technical products of poly acrylic ester or amide containing free carbonic acid residues, together with poly vinyl-alcohol (PVA), which is not a hardener in itself for gelatine, and found that best results were obtained in the cases of using PVM/MA or PA as a hardener in gelatine with an appropriate amount of PVA.