Re: SWOP, SNAP, GRACOL Paper Grades Question
Michael:
Very important metric, but only tracked at the mill. Costs a lot of money to measure smoothness. Done in a lab like GATF or a vendor. Two methods: Sheffield smoothness, an air leak method, best suited for uncoated paper; and the better method, Parker Print Surf, PPS for acronym junkies, is air leak with a "blanket like" surface, best for coated paper. The closest you might get in something like the Paper Grade Finder is Gloss, which is an indirect measure of smoothness. Well, so is air leak. When you print on plastic, the wise printer measures surface roughness, R(a) with a a surface profilometer. These toys can cost $10,000 to $20,000. Still, a very important metric. Blanket suppliers use R(a) too.
John Lind
Cranberry Township, PA
724-776-4718