Keeping up Appearances

Northwest Coatings Water Base Technical Manager Charles Wasserman says coldseal/cohesive difficulties arise when coated onto metallized or clear films. He counts three chief appearance problems encountered in such scenarios as streaking; uneven surfaces; and voids, craters, and crawling.

Streaking, Wasserman reveals, is caused by material build-up under the doctor blade, and evinces itself in the land area of an applied pattern. An oscillating doctor blade and micro-etching of the cylinder land areas often corrects the problem. Alternatively, the printer should employ a slower-drying and higher-stability coldseal/cohesive.