ISO 3781:2011 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. It is not applicable to tissue paper and tissue products other lightweight, highly absorbent paper which is difficult to handle or of low strength when wet (see ISO 12625‑5).