Moisture-induced dimensional changes have a large 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 thus a major concern of any producer of paper, print or packaging. For a long time, however, no method has been available for measuring the hygroexpansion in a flexible, effective and accurate manner.

New effective test equipment

Innventia has recently developed new test equipment to measure the hygroexpansion of paper materials. This equipment is both labour- 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.

 

The hygroexpansivity tester is fully automatic.