Although soap was known in England in the 14th cent. The industry was handicapped in England from 1712 to 1853 by a heavy tax on soap. The manufacture of soap was stimulated by Chevreul's discovery of oleic and stearic acids in the early 19th cent. Chemically, soaps are metallic salts of fatty acids . A number of methods may be employed to make soap, but all are based on the same principle of operation.
Salt is added, and the soap then forms a light curd that floats to the surface.
Glycerol, a valuable byproduct, can be distilled from the liquid residue. It is thoroughly churned, poured into huge frames, cut with wires, shaped, and stamped. Hard-milled soap is run over chilled rollers and is scraped off as chips which are rolled into ribbons, cut, and shaped. Soap is marketed also as chips, flakes, and beads and in powdered form. Soap powders, as distinguished from powdered soap, contain builders that assist in rough cleaning.