Transparence or translucence of the surface film produced in polishing metals

In a communication to the British Association it was suggested that all smooth metal surfaces are covered with an enamel-like transparent layer. In a subsequent communication to the Royal Society the actual formation of a surface layer or skin by polishing was demonstrated. Two of the photo­micrographs in the latter paper (figs. 5 and 6, Plate 9) showed that minute pits on a polished surface of antimony had been covered over by a film of this description. It was suggested that the diminished reflecting power of the film covering the pits probably indicated that it had become trans­lucent, but no direct evidence of this translucence was afforded by these particular observations. It was also suggested that the film might have been carried across the pits on a support provided by small granules or flakes which had filled up the pit to the level of the general surface. The purpose of the present communication is to record and illustrate certain recent observations which show:— (1) That the film which covers the pits is transparent, or at any rate highly translucent: and (2) That in the case of the smaller pits the mobile film has been carried across the empty pit without any support from below.