Details:
Summary:
In this system, water is applied to the plate by a metal roller spaced 0.004 in. from the plate surface, after which an air blade removes the excess water. The water discarded is pulled into a vacuum chamber. The air blade slot is 0.010 in. wide and is set 0.015 in. from the plate surface. The air pressure is quite low. Fountain solutions ranging in pH from 3.5 to 8.0 have been handled successfully. Operation is fairly independent of press speed, and no plate scum has been encountered. Advantages claimed are: (1) Less water is used, reducing ink emulsification and paper curl. (2) The system works equally well on line and halftone copy. (3) Problems with damper coverings are eliminated. (4) Regardless of the plate surface, a very thin uniform film of moisture is applied. (5) A change in thickness of the film can be effected within a single revolution of the press. (6) Once established, water film thickness remains unchanged.