Measuring Hygral Expansion in Woven Wool Fabrics

Abstract

Hygral expansion measurements of woven wool fabrics are influenced by the way in which wet fabric, after relaxation in water, is dried. If the wet fabric is dried directly in an oven, the hygral expansion values are relatively low, but if the fabric is allowed to dry under ambient conditions before oven drying, the values are relatively high (and closer to the "true" values). An interlaboratory trial conducted using thirteen commercial worsted fabrics includes a statistical analysis of different methods for determining the magnitude of hygral expansion. The fabric drying conditions have an important bearing on the magnitude of the dry dimension, and this in turn influences the hygral expansion value obtained.