Processes for Fireproofing Wood
Considerable attention has been given in the United Kingdom to the best method for fireproofing wood, especially in connection with railroad construction. The following is a description of a process which, it is claimed, has received the favorable consideration of the British Admiralty. The wood is placed in large iron cylinders, the doors of which are hermetically sealed. The wood is then subjected to a course of steaming, and under vacuum the air and moisture in the pores of the wood are removed and the sap vaporized. The fire proofing solution is thereafter run into the cylinders, and under pressure forced throughout the pores and fibers. Subsequently the water in the solution is evaporated in drying kilns, and the chemicals, in minute crystal form, arc left embedded in the wood. When heat is applied these crystals expand to many times their original size, forming a glassy coating to the fibers of the wood which excludes the oxygen in the air. In time the heat causes the crystals to collapse, but further crystals in the wood immediately expand, and the same process of resistance against fire continues. The chemicals used are antiseptic and preservative, consisting chiefly of phosphate of ammonia. As a result of the treatment, the life of the wood is also lengthened, for the cause of decay (sap water) is eliminated. This process is claimed to be especially satisfactory, inasmuch as the material treated is not saturated with a solution of salt, nor are such chemicals used as tungstate of soda, sulphate of ammonia, sulphate of alumina, alum, etc., which invariably cause discoloration of the wood, corrosion of metals, destruction of fibers, and prevent satisfactory painting or polishing. After this treatment the wood can be worked, nailed, glued, painted, polished, etc., as though it had not been subjected to any special process. All kinds of timber can be treated.—Consul-General John L. Griffiths, London.