This part specifies a method for the determination of hygroexpansivity when the paper or board is subjected to a change in the relative humidity with which it is in equilibrium from (33 2) % to (84 2) %. The purpose is to cover applications of paper and board intended to be used in high humidity conditions. It may also be useful in determining the effect of excessive moisture to which paper may be subjected for short periods during some printing processes. The method is generally applicable. However, it is not suitable for cr pe papers and corrugated fibreboard.