Technical Bulletin No. 0096: Freeness of Paperboard Stock as Affected by Biological and Other Factors

National Council Technical Bulletin Number 34, published in 1950, dealt with factors affecting the reuse of white waters and clarifier underflow in board mills. This paper attracted considerable interest since the research reported therein gave some clues as to the effect of undesirable constituents in returned water on stock freeness. For this reason, research in this direction was continued and the effect of a multiplicity of factors was investigated by the Rutgers University Project of the Council. Results of this experimental work is reported in National Council Technical Bulletin Number 96, which is attached. This work indicated that the common additives employed in papermaking had little effect on freeness when re-circulated. Fiber fines as well as slime growth were found, under some conditions to have appreciable effect on freeness. The effect of slime growth appears to be related to system water velocities. Where velocity is high, slime growths remain or are dispersed causing little freeness change, while agglomeration occurring at low velocity can cause appreciable lowering of freeness.