The Nature of Single Fiber Kappa Distributions

We examined the uniformity of a variety of kraft pulps with the University of Washington’s single fiber kappa analyzer (FKA). Some consistent patterns and trends with regard to pulp uniformity have emerged. This paper provides a synthesis of the significant observations we made in examining the kappa uniformity of kraft pulps. Hardwood pulps are generally more uniform than pulps from softwoods, but all the single fiber kappa distributions are broad. Virtually all softwood pulps have high kappa tails, whereas hardwood pulps have a high kappa tail only if the pulping is extremely non-uniform. Hardwood pulp kappa distributions appear to be Gaussian. Softwood pulps from commercial digesters are generally much less uniform than those made in the laboratory. The differences in uniformity in hardwood pulps from laboratory and commercial digesters are less dramatic than for softwood pulps. Hardwoods that we have examined appear to be much easier to pulp with uniformity than softwoods.