LINOLEUM

smooth-surfaced floor covering made from a mixture of oxidized linseed oil, gums and resins, and other substances, applied to a felt or canvas backing. In the original process for manufacturing linoleum, a thin film of linseed oil was allowed to oxidize. Since oxidation proceeds mainly on the surface, fresh oil was continually applied to the surface of the oxidized film. After weeks of exposure, during which the thickness of the oil film reached an inch or more, the oxidized oil was fluxed with a natural resin. Cork and other fillers were mixed with the resin and oxidized oil. This process was eventually replaced by a faster method in which linseed oil is oxidized in large cylindrical kettles where the oil is stirred at elevated temperatures. The oxidization is continued until the oil barely flows at reaction temperature; then the oil is blended with resin in heated kettles and the mixture is exposed to hot air. The plastic material of high viscosity that forms is blended with wood flour and whiting. The binder, fillers, and pigments are mixed, then calendered into sheet form between rollers and applied to a backing of felt or canvas saturated with asphalt. The backed linoleum is hung in tall buildings or stoves, which are heated to harden the linoleum. The hardening process may take weeks. Modern manufacturing methods are used to produce plain and inlaid, or printed, decorative patterns. Inlaid patterns are made by cutting squares out of two differently coloured linoleum sheets and attaching them to the backing material. Marble effects are achieved by mixing blends of two or more colours, and other effects are obtained by granulating mixes of variously coloured sheets, applying these crumbled materials through stencils to a backing, and then pressing them into sheet form again. Linoleum is resilient, warm, unaffected by reasonable floor temperatures, and does not readily support combustion. It is specially hardened to resist indentation and is not susceptible to damage from fats, oils, greases, or organic solvents, but moisture and certain alkalies will attack it after prolonged contact.