IMPROVEMENT OF PRINTABILITY OF MECHANICAL GRADES WITH PRE-CALENDERING

Paper samples, collected from the dryer sections of commercial machine s were treated with a Hydra-Nip pre-calender. pre-calendering can incr ease gloss by up to 5 points and reduce Parker Print-surf roughness by up to 0.9 mu m without significant strength loss, over existing machi ne calendering. Pre-calendering when combined with soft calendering gi ves additional improvements in gloss and smoothness. Print quality, as measured by print density index, increases significantly, particularl y on the side that contacts the heated metal roll in the last nip.