Water release from fractionated stock suspensions. Part 1 – Effects of the amounts and types of fiber fines

Cellulosic fines produced varying resistance to dewatering in tests with a gravity-based freeness device. Fines at low to moderate levels had little effect on gravity dewatering, but fines slowed drainage considerably as their concentration increased beyond a threshold. Fines created by refining (secondary fines) slowed drain-age to a much greater extent than did those originally present in bleached hardwood kraft pulp (primary fines). The results were consistent with a mechanism in which unattached fines can migrate within a wet web to choke points, where they tend to block the flow of water.