Print mottle shows as patchy color density in solids and halftones, and gloss mottle as patches of shine and dullness, both usually a few millimeters across. Causes include uneven coat weight, binder migration, poor formation under a thin coating and uneven ink absorption between units of a multicolor press. Back-trap mottle, where blankets in later units unevenly lift ink printed by earlier ones, is the classic offset version.
Back-trap mottle again on the four-color solids, so pull the coat weight profile and binder level for that run.
Also heard as
- mottling
Related terms
Print gloss
Gloss of the printed ink film on a paper, as distinct from the gloss of the bare sheet.
Formation
How evenly fibers are spread through a paper sheet, judged by small-scale variation in mass.
Coat weight
Mass of dry coating applied to paper per unit area, usually stated per side in grams per square meter.
Ink holdout
The ability of a paper surface to keep ink and its vehicle on top instead of absorbing them.