Moisture-induced dimensional changes have a significant effect on the runnability of paper and paperboard in converting operations. This phenomenon of hygroexpansion is also largely responsible for web and reel defects such as curl, twist, cockling, waviness and long edges of the paper material.

The hygroexpansion of the paper is a major concern for any producer of paper, print or packaging. For a long time, no method has been available for measuring the hygroexpansion in a flexible, effective and accurate manner.

The method can predict dimensional changes of paper when the moisture changes, e.g. during printing or end-use.

RISE has developed a new test equipment to measure the hygroexpansion of paper materials. This equipment is both labour-effective and time-effective, since it is fully automatic and allows 30 independent hygroexpansion tests to be run at the same time. The equipment is connected to a moisture generator which can be programmed to make measurements possible under optional humidity histories in the interval 10 %RH to 90 %RH.

We can provide hygroexpansion coefficients, and also a description of how dimensional changes occurs.