Full Description

This method applies to the measurement of the drainage time of coarse, easily dewatered, insulating-board pulps. The apparatus described in TAPPI T 221 "Drainage Time of Pulp" and also T 227 "Freeness of Pulp" were designed for papermaking pulps that dewater more slowly than insulating-board pulps. As a result, neither apparatus differentiates well in between the rapidly dewatering pulps used for insulating boards. Only by concentrating the major resistance to the flow of water at the fiber pad under test can the best differentiation be obtained, and even then it is not very marked, particularly with the coarser grades of fiber normally used for insulating board. For this reason, a special apparatus has been designed.

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