The document specifies a method for the determination of the drainability of a pulp suspension in water in terms of the Schopper-Riegler (SR) number. The Schopper-Riegler test is designed to provide a measure of the rate at which a dilute suspension of pulp may be dewatered. It has been shown that the drainability is related to the surface conditions and swelling of the fibres, and constitutes a useful index of the amount of mechanical treatment to which the pulp has been subjected.#,,#