In 1970, it was learned that a PTFE micropowder in combination with wax greatly increased the rub resistance of printing ink. An early investigation of the mechanism was done by printing on a transparent substrate and rubbing with paper. The microscope was then used to study the appearance.   Fig. 1: Liquid appearance of the wax suggests pressure melting. Some of the rub streaks caused by the paper fibers had the appearance of a flowing liquid, which was interpreted as the wa...