In an offset press's continuous-flow dampening system, the line of contact between two rollers rotating in the same direction, typically a hard transfer roller and a form roller, either belonging to the dampening system, or shared by the dampening and inking systems. When two adjacent rollers rotate in the same direction (either clockwise or counterclockwise), at the line of contact (the nip) they are moving in opposite directions, preventing the fountain solution transferred by the rollers from flowing into the nip. A reverse slip nip is occasionally produced in presses as a means of preventing interaction between excess fountain solution returning from the plate and "fresh" fountain solution flowing out of the fountain pan. Preventing this interaction allows greater control, or metering, of the fountain solution flowing to the plate. A more or less "conventional" nip between two rollers rotating in opposite directions is called a slip nip. (See Dampening System.)
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