In a process for the production of porous masses suitable for heat or sound insulation or as fillers for life belts or similar articles, by dissolving or dispersing a composition comprising a cellulose ester and/or ether in a small quantity of solvent to form a plastic mass, mixing therewith a filler and dissolving out the filler during or after pressing, the filler is sufficiently finely ground to pass through a 100 mesh sieve. In an example, 180 grams of cellulose acetate are swollen with 9 ccs. of tricresyl phosphate and 360 ccs. of a mixture of 85 per cent tetrachlorethane and 15 per cent alcohol by volume. 3,6 kgms. of sodium chloride ground to 100 mesh are added, and the mass pressed for 2 or 3 minutes in a press one foot square to a thickness of one inch at a temperature of 95--100 DEG C. and a pressure of 1 ton/sq. inch. The cake is dried at 80--100 DEG C. for about 6 hours and washed in running water for about 24 hours and then again under slight pressure or vacuum to eliminate the sodium chloride. The mass is then dried. Other examples are given in the Specification, which includes the use of any ester or ether of cellulose with any of the known solvents, and any soluble filler, which includes practically all soluble salts, preferably sodium chloride, anhydrous sodium sulphate or calcium chloride. In a modification, the filler is a by-product obtained in the manufacture of acetic anhydride and consisting of an anhydrous mixture of sodium chloride and sodium sulphate which passes readily through a sieve with 250 meshes to the inch. The mixture may be rendered free from objectionable smell by admixture of a little finely divided calcium carbonate. Fibrous fillers such as asbestos fibres, silk fibres, cellulose fibres, or hair, may be incorporated in the mass, and substances reducing inflammability, e.g. triphenyl phosphate, tricresyl phosphate, magnesia, metallic silicates or phosphates may also be added. Substances such as tin phosphate silicate may be used to raise the melting point of the mass. Plasticizers are not necessary when triphenyl or tricresyl phosphate are used, but may be added alone or with one of the agents which reduces inflammability. Examples are dibutyl phthalate, triacetin, phthalic esters of ethyl alcohol, butyl alcohol and glycol and cyclohexyl esters of adipic acid. Colouring matter may be included if desired. The mass may be rendered impenetrable to gases and liquids by applying a suitable composition, for instance, a benzyl cellulose coating composition or a cellulose nitrate composition to the surface of the material. The Specification gives some of the physical properties of the material produced according to the invention and compares it with other materials. Specifications 23196/13, [Class 2 (ii)], 228,844, and 305,020, [both in Class 70], are referred to. According to the Provisional Specification, the mass may be coated with solvents applied by brushing or spraying, or with synthetic resins, or with rubber. Two or more of the masses may be joined with adhesives, and pieces of fabric like cotton gauze may be introduced into the masses or applied as coverings thereto. Such coverings may then be coated with synthetic resins, rubber or other suitable substances.ALSO:In a process for the production of porous masses suitable for heat or sound insulation or as fillers for life belts or similar articles by dissolving or dispersing a composition comprising a cellulose ester and/or ether in a small quantity of solvent to form a plastic mass, mixing therewith a filler and dissolving out the filler during or after pressing, the filler is sufficiently finely ground to pass through a 100 mesh sieve. In an example 180 grams of cellulose acetate are swollen with 9 ccs. of tricresyl phosphate and 360 ccs. of a mixture of 85 per cent tetrachlorethane and 15 per cent methyl alcohol by volume. 3,6 kgms. of sodium chloride ground to 100 mesh are added, and the mass pressed for 2 or 3 minutes in a press one foot square to a thickness of one inch at a temperature of 95-100 DEG C. and a pressure of 1 ton per sq. inch. The cake is dried at 80-100 DEG C. for about 6 hours and washed in running water for about 24 hours and then again under slight pressure or vacuum to eliminate the sodium chloride. The mass is then dried. Other examples are given in the Specification, which includes the use of any ester or ether of cellulose with any of the known solvents, and any soluble filler, which includes practically all soluble salts, preferably sodium chloride, anhydrous sodium sulphate or calcium chloride. In a modification the filler is a by-product obtained in the manufacture of acetic anhydride and consisting of an anhydrous mixture of sodium chloride and sodium sulphate which passes readily through a sieve with 250 meshes to the inch. The mixture may be rendered free from objectionable smell by admixture of a little finely divided calcium carbonate. Fibrous filters such as asbestos fibres, silk fibres, cellulosic fibres, and hair may be incorporated in the mass, and substances reducing inflammability, e.g. triphenyl phosphate, tricresyl phosphate, magnesia, metallic silicates or phosphates may also be added. Substances such as tin phosphate silicate may be used to raise the melting point of the mass. Plasticisers are not necessary when triphenyl or tricresyl phosphate are used but may be added alone or with one of the agents which reduces inflammability. Examples are dibutyl phthalate, triacetin, phthalic esters of ethyl alcohol, butyl alcohol and glycol and cyclohexyl esters of adipic acid. Colouring matter may be included if desired. The mass may be rendered impenetrable to gases and liquids by applying a suitable composition for instance a benzylcellulose coating composition or a cellulose nitrate composition to the surface of the material. The Specification gives some of the physical properties of the material produced according to the invention and compares it with other material. Specifications 23196/13, 228,844, and 305,020, [all in Class 70], are referred to. According to the Provisional Specification, the mass may be coated with solvents applied by brushing or spraying, or with synthetic resins, or with rubber. Two or more of the masses may be joined with adhesives, and pieces of fabric like cotton gauze may be introduced into the masses or applied as coverings thereto. Such coverings may then be coated with synthetic resins, rubber or other suitable substances.