Reverse shrinkage means just what it sounds like. In wovens, reverse shrinkage is most often due to chemical properties of the fabric and if not dry cleaned, the weave will loosen from its previously crisp state and get billowy. Is billowy a word? This happens a lot with inexpensive rayons -as I would know from shopping the dollar a yard bins so it serves me right. Sure, you pay less for fabric but the pass along cost to the consumer is higher on account of maintenance.
Reverse shrinkage in knits is usually due to something else. We’ve all experienced it. You buy a shirt, skirt or slacks and after one washing, the garment is wider than before. Do you know why this is? Believe me, you don’t want to find out about reverse shrinkage the hard way when people start sending the stuff back. They can send it back because it’s a manufacturing defect, not a fabric flaw.
If you think you know the answer, let us know in comments. If you know the cause, you also know how to prevent it so be sure to explain that too. Thanks!