The Polishing of Surfaces

Abstract

IN NATURE of Sept. 4, 1926, Mr. J. M. Macaulay suggested that, in the process of polishing, surface layers were actually melted—the energy supplied being ample to produce melting, and the difficulty with regard to temperature disappearing if the heat, due to friction, was produced at points of contact rather than over large areas (the temperature at a mathematical pointsource of heat being infinite). In NATURE of Jan. 29, Mr. N. K. Adam contends that “it does not seem necessary to suppose that actual liquefaction occurs,” since “the polisher will tear away the surface particles of the glass” and “some of these particles will naturally be redeposited elsewhere at random, thus forming the amorphous layer.” Now it is difficult to believe that particles of glass spread at random will have a polished surface, even although these particles be of molecular dimensions, since each particle will be covered by a surface layer of gas, or other substance, which will prevent cohesion at ordinary temperatures. It might be contended that in the polishing process the particles torn from the surface had no time to assume a surface layer, but that is surely a highly improbable assumption. It seems to me that Mr. Macaulay's letter gives the key to the rational explanation of surface polish.