oriented or strength - enhanced embossed film is produced by introducing a thermoplastic film having an inert liquid lubricant covering its surfaces into the nip between at least one pair of rotating compression rolls under sufficient pressure to reduce the thickness of the film , and simultaneously embossing at least one of the film surfaces within the nip . while various inert liquids may be used as the lubricant , use of water for this purpose is preferred . the lubricant is believed to provide a hydrodynamic wedge at the film - compression roll interfaces , and for best results it is preferred to spray the lubricant into both incoming sides of the nip of the compression rolls .