Effect of Blanket Properties on Print Quality

Five blanket types were evaluated against four printing surfaces (two papers and two board samples) with respect to selected printability parameters. Testing was conducted using a Heidelberg 5-color press. During the trials, no piling was noted. Back-trap mottle was measured instrumentally and visually. Except for one sample that had a coating defect, the instrumental results indicated that there was little difference in mottle between print substrates or blankets. Visually, however, differences were seen and, in general, the non-compressible blanket surface looked the worse. The severity of the mottle seen with this blanket is highly dependent on the impression setting between it and the substrate. With respect to print gloss, blankets, in general, did not have any major influence. Ink position on the press did, however. The gloss of the 1st down cyan (C1) was several points higher than that of the 5th (and last) down cyan, C5. This is attributable to ink-paper interactions that are not apparently related to blanket roughness, nor the ink absorptivity of the substrate. Dot gain was affected by the choice of blanket; a substrate-dependent increase in dot gain, and corresponding decrease in print contrast, being observed with one blanket. This is attributable to the nature of this blanket's surface.