Casein condensates in stable aqueous form are prepared from acid-casein brought into solution with the aid of a substance of alkaline reaction, urea or thiourea or a mixture of both, and formaldehyde, by heating an aqueous solution of these substances until a colloidal mixed condensate is formed, diluting the latter with water as soon as it reaches a thick colloidal consistency and before it reaches the water-insoluble condition and immediately cooling the diluted solution to ordinary temperature. The condensing solution may be prepared by making an aqueous glue from the casein and alkaline compound, adding the urea and/or thiourea and then adding the formaldehyde. A part of the urea or thiourea may be replaced by another substance containing amino-groups and capable of resin-forming condensation with formaldehyde such as biuret, dicyandiamide or melamine. If desired, further substances may be added which, at least in part, enter into the structure of the resinous product, for example, water-soluble alcohols. A buffer solution may be added, before or after the condensation, to stabilize or modify the acid-reaction of the mixture. The products may be combined with other binding or adhesive substances such as reversible casein glues, other water-soluble synthetic resins and products obtained by the polymerization of polymerizable monomeric compounds in general, cellulose esters, starch, dextrin, softening agents, filling materials and pigments; they may be used in emulsions with water-immiscible organic solvents, lacquers, drying oils, oil-soluble synthetic resins, rubber or derivatives thereof and waxes such as paraffin wax. They find application in paper, wood, leather and textile industries and in combatting pests. According to examples, aqueous solutions of binding agents are prepared from formaldehyde and (1) urea and acid-casein in triethanolamine solution; (2)-(3) a sodium citrate solution and a casein solution containing either thiourea and trisodium phosphate or urea, thiourea, borax and glycol, both obtained as described in examples (5) and (4) respectively of Specification 597,390; (4) an aqueous solution of guanidine carbonate, casein, urea and dicyandiamide; (5) urea, thiourea, melamine, borax, cyclohexanol and the purified casein solution obtained as in example (3) of the above-mentioned Specification. The Specification as open to inspection under Sect. 91 states that the agents may be prepared from any carbamide. This subject-matter does not appear in the Specification as accepted.ALSO:Hardenable binding agents in stable aqueous form are prepared from acid casein brought into solution with the aid of a substance of alkaline reaction, urea or thiourea or a mixture of both, and formaldehyde, by heating an aqueous solution of the aforesaid substances until a colloidal mixed condensate is formed, diluting the latter with water as soon as it reaches a thick colloidal consistency and before it reaches the water-insoluble condition, and immediately cooling the diluted solution to ordinary temperature. Generally, in making the condensing solution an aqueous glue is prepared from the casein with the aid of the alkaline substance, then the urea and/or thiourea is added, a part of which may be replaced by another compound containing amino-groups and capable of resin-forming condensation with formaldehyde such as biuret, melamine, dicyandiamide or the like and finally the formaldehyde is added in aqueous solution or in solid form. If desired, further substances may be added which, at least in part, enter into the structure of the resulting products, for example, water-soluble alcohols. The normally acid-reaction of the mixture may be stabilized or modified before or after the condensation by addition of a buffer solution. The binding agents may be combined with other binding or adhesive substances (see Group V), emulsified with oily constituents and generally, find application in the paper, wood, textile and leather industries and in combating pests. According to examples, solutions of binding agents are prepared from formaldehyde and (1) urea and acid casein in aqueous triethanolamine solution; (2)-(3) a sodium citrate solution and a casein solution containing either thiourea and trisodium phosphate or urea, thiourea, borax and glycol, both obtained as described in examples 5 and 4 respectively of Specification 597,390; (4) an aqueous guanidine carbonate solution of casein, urea and dicyandiamide; (5) urea, thiourea, melamine, borax, cyclohexanol and the purified casein solution obtained as in example 3 of the above-mentioned Specification. p The Specification as open to inspection under Sect. 91 states that any carbamide may be used in forming the binding agents. This subject-matter does not appear in the Specification as accepted.ALSO:Adhesives comprise the hardenable binding agents in stable aqueous form prepared from acid-casein brought into solution with the aid of a substance of alkaline reaction, urea and thiourea or a mixture of both, and formaldehyde, by heating an aqueous solution of these substances until a colloidal mixed condensate is formed, diluting the latter with water as soon as it reaches a thick colloidal consistency and before it reaches the water-insoluble condition and immediately cooling the diluted solution to ordinary temperature. A part of the urea or thiourea may be replaced by another compound containing amino-groups and capable of resinforming condensation with formaldehyde such as biuret, dicyandiamide or melamine; further substances may be added, if desired, which at least in part enter into the structure of the resinous product, for example, water-soluble alcohols. A buffer solution may be added to stabilize or modify the acid-reaction of the solution before or after the condensation. The products may be combined with other binding or adhesive substances such as reversible casein glues, other water-soluble resins and polymerised compounds in general, cellulose esters, starch, dextrin, softening agents, fillers and pigments; they may be used in emulsions with water-immiscible organic solvents, lacquers, drying oils, oil-soluble synthetic resins, rubber or derivatives thereof, and waxes such as paraffin wax. Examples describe the preparation of the casein products used as adhesives (see Group IV (b)).