Expose sensitized metal plates to positive or negative films.
What does a Lithographic Platemaker do?
Exposes sensitized metal plate to positive or negative film, using vacuum frame, to produce offset lithographic printing plates: Punches holes in light-sensitive plate with register punch and inserts register pins in holes to prepare plate for contact with positive or negative film. Places plate on bed of vacuum frame and inserts positives or negatives on register pins to align positives or negatives with each other and with plate. Places masking paper on areas of plate not covered by positives or negatives to prevent exposure of those areas. Lowers top of vacuum frame onto plate and film assembly and activates vacuum to maintain contact between negative or positive film and plate. Sets timer to activate ultraviolet light that exposes plate to positives or negatives. Removes plate and film assembly from vacuum frame and places exposed plate in automatic processor to develop image and dry plate. Performs tests to determine time required for exposure by exposing plates and comparing exposure to gray scale. May replenish chemical solutions in automatic plate processor to maintain processor in working order. May expose plates, using step-and-repeat machines. May make proofs.