This International Standard specifies a test method for the determination of the wet tensile strength of paper or board after its immersion in water for a specified period. In principle, the method is applicable to both paper and board, provided an appropriate soaking time is agreed between the interested parties. This International Standard is not applicable to tissue paper and tissue products or other lightweight, highly absorbent paper which is difficult to handle or of low strength when wet (see ISO 12625-5[1]). NOTE The tensile strength testing is performed using an apparatus operating at a constant rate of elongation of 20 mm/min, as per ISO 1924-2, or 100 mm/min, as per ISO 1924-3. Therefore, depending on which method is chosen, only one or the other of those International Standards is needed for performing the test.