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TAPPI T 227 Pulp freeness






Freeness of pulp (Canadian standard method)


TAPPI T 227 pulp freeness, is designed to give a measure of the rate at which a dilute suspension of pulp (3 g of pulp in 1 L of water) may be drained. The freeness, or drainage rate (see TAPPI T 221 “Drainage Time of Pulp”), has been shown to be related to the surface conditions and swelling of the fibers. Besides these factors, the result is dependent also on conditions under which the test is carried out, such as stock preparation, temperature, and water quality. The applicability of this method to all types of pulps has not been determined.


The procedure was originally designed to yield a test value suitable primarily for the control of manufacture of groundwood. It is also widely used to follow the changes in drainage rate of various chemical pulps during beating and refining. Treatments which produce a large proportion of fines may sometimes cause an anomalous rise of freeness (false freeness) usually at values below 100 mL. Freeness values do not necessarily correlate with the drainage behavior of pulp material on a commercial paper machine.


To perform adequate testing on a dry sample 30 oven dry grams are desired and the equivalent of 10 oven dry grams are desired from slush samples. This ensures proper disintegration and that a duplicate can be run on each sample to be tested. If sample availability is limited, testing can be performed using less sample or as a single determinant. IPS calculates the freeness corrections based on the tables in the method.


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SGS-IPS cannot sell or otherwise provide standards, specifications, or test procedures to third parties.