Lightweight Coated #5 Publication Grade Print Benchmarking Study and Assessment of Laboratory Gloss and Roughness Test Methods, 2000 International Printing & Graphic Arts Conference Proceedings

Linda Kim-Habermehl, Mario Seixas, Joann Surma, David A. Smith--This heatset web offset printability study provided a recent “snapshot” of printed paper performance for nine commercial No. 5 lightweight coated (LWC) papers, spanning a basis weight range of 48 g/m 2 (32 lb) to 57 g/m 2 (38 lb). Results show that, from 1991 to 1998, the brightness limits of the most popular U.S. brands of LWC offset #5 grades have risen by 0.5%, while basis weights have dropped from about 60 g/m 2 (40 lb) to a range of 48 – 57 g/m 2 (32lb – 38 lb). Ink gloss rose while sheet gloss dropped, illustrating the end-use importance of delta gloss and readability. The highest ink snap samples (printed ink gloss minus sheet gloss) were found across all the basis weights. Ink trapping efficiency improved and gloss two-sidedness decreased. There were no incidents of, or differences in, mottle or granularity in the solids or halftone screens. Visual printed roughness fiber rise) was generally worse for the lighter weights, as expected. Severity of fluting did not correlate with basis weight.

Pre-dampening the paper, in a prüfbau heatset ink gloss method, yielded the best correlation (r = 0.80) to press trial ink gloss. The opposite conclusion was drawn for the best roughness correlation of the non-image area: a simple dry run through the oven was significantly correlated. There was no correlation between visual roughness and 75-degree ink gloss or between Monitor roughness measurements and 75-degree sheet gloss.