macule

In letterpress and relief printing, maculing occurs when an impression shifts or doubles on the paper, leaving a blurred or ghosted image alongside the intended sharp print. The term comes from the Latin macula, meaning spot or stain. On press, this manifests as a secondary, offset version of the type or image that overlaps the primary impression, typically offset by a fraction of an inch. The result is legible but visibly degraded, often resembling a shadow or smear rather than a clean strike.

Maculing most commonly happens when the platen (the hard backing surface) shifts slightly during the impression stroke, or when paper moves between the first and second contact of type and substrate. In hand presses, excessive impression pressure combined with soft packing can cause the platen to yield and recover unevenly, pushing the sheet sideways. On powered cylinder presses, worn bearings, loose gripper settings, or a platen that lacks uniform hardness across its face will generate these double impressions consistently.

Where maculing appears in production

The defect most often strikes near the end of long print runs, after the platen or impression rollers have worn. It also appears when printers switch between stock weights without readjusting packing or impression screws. On multicolor presses, maculing on one color station goes undetected until the sheet reaches the second color, where the misalignment compounds. Spot checks at the press are the only reliable catch; maculed sheets slip through to binding if they are not culled.

Fixing maculing requires identifying whether the platen has moved (check levelness with a straightedge), whether paper is slipping in the grippers (tighten or replace), or whether packing has compressed unevenly (replace with fresh, uniform stock). On older presses, worn platens must be recovered or replaced to restore a dead-flat, rigid striking surface. The term is less common in offset and digital printing, where impression pressure is gentler and platen movement is not a factor.