Pure rayon shrinks when washed or dried if it has not been pretreated when manufactured. Rayon is a delicate fabric that was originally designed as a dry clean only material. Blended rayon with a 30 percent or more ratio of polyester is normally safe in the washer or dryer.
When rayon is wet, its strength is decreased by as much as 50 percent. Washing in a machine can break down the fabric from the repeated agitation. Dryers only increase the chances of damaging the fabric. The result is a loss of softness with the rayon often feeling stiff and scratchy.