This International Standard specifies a method for the determination of the water absorption of paper and board after total immersion in water for a specified time. The method is applicable to all types of paper and board which have a degree of water resistance. It is not applicable to very absorbent papers such as toilet tissue. NOTE — The method is analogous to that specified in ISO 769:1972, Fibre building boards — Hard and medium boards — Determination of water absorption and of swelling in thickness after immersion in water.