This International Standard describes the procedure for determining the fines mass fraction of all kinds of pulp by means of a perforated metal plate or a single-screen fibre classifier (Dynamic Drainage Jar or similar). The screening procedure is the same for all pulps, although the mass of the test portion and the total volume of water for screening are not the same. NOTE The procedure is also applicable for most kinds of paper samples, provided that it is possible to fully disintegrate the sample.