FIREPROOFING. The coating or impregna tion of combustible materials, such as textile fabrics and wood, with chemical preparations so as to prevent their burning either partially or entirely. Such substances for the most part act by coating the material with a crust of mineral matter on the surface of the fibres that serves to prevent combustion, but does not interfere with decomposition. Cotton or linen may be steeped in any saline solution, such as alum, ammonium chlo ride, ammonium phosphate, borax, sodium phos phate, and sodium tungstate, in order to render them incombustible. It is said that muslin dipped or washed in a solution containing 20 per cent. of sodium tungstate is perfectly non inflammable when dried. Preparations of these salts in various combinations and proportions find extensive use for the treatment of canvas used for scenery in theatres, and in many places it is required by law that the drop-eurtain shall be fireproof. Papers that are both fireproof and waterproof may be made from a pulp consisting of vegetable fibre to which asbestos and salts, such as alum and borax, in suitable proportions, have been added.
For the fireproofing of timber a number of processes have been invented, and include the impregnation of the wood with such salts as iron sulphate and calcium chloride, sodium silicate, sodium tungstate, zinc chloride, and even com mon whitewash. A similar result is frequently obtained by means of so-called fireproof paints. These include paints in which sodium silicate and zinc chloride have been incorporated. A preparation consisting of boric acid, sodium borate, soluble cream of tartar, ammonium sul phate, potassium oxalate, and glycerin mixed with glue and incorporated with a paint, has been usual in Paris as a fireproofing paint in the theatres. A mixture of these salts may also be used to render fibrous materials fireproof. See FIREPROOF CONSTRUCTION.