Return-facing
The use of return-facing is confined principally to foundries manufacturing thin, light castings, as stoves, etc.; where, having no coal mixed through the sand, means must be provided, not only to scale the casting clean, but leave the color uniform throughout. To effect this the raw sand surfaces of the moulds are first treated to a dusting of bolted hydraulic cement or German clay (a cheap substitute for heavy carbon-facing) to fill the pores of the sand, then a light dusting of heavy facing, and, lastly, the return-facing in just sufficient quantity to permit the pattern, when returned, to leave its impression sharp and smooth without sticking. The carbonized preparations of return-facings supplied by the dealers are, as a rule, preferable to the light charcoal-facings usually employed for this purpose, as they neither run before the metal nor adhere to the pattern as much as charcoal is liable to. See PRINTING; FACING.