If you wash a sweater that is 100 percent wool, the warm water and agitation can cause it to felt and shrink. Felting is a result of the wool fibers rubbing together, which can erase the visibility of the knit or crochet stitches. While a sweater that has felted will never look like it did before due to the alteration of the fibers, you may be able to stretch it back out with a process called blocking.
Wash the sweater by hand in a sink full of cold water. Use a capful of silicone-free hair conditioner instead of soap, and stretch the sweater gently in the water without agitating it.
Roll the sweater like a jelly roll in a large absorbent towel, gently pressing out any excess water.
Cover a soft surface with another large towel. A bed or sofa works well. Lay the sweater on the towel
Stretch the sweater back into shape and pin it all the way around the edges, inserting a pin every 1 to 2 inches.
Allow the sweater to air-dry completely. Depending on the thickness of the wool and the climate, this can take up to two days.
Ann Jones has been writing since 1998. Her short stories have been published in several anthologies. Her journalistic work can be found in major magazines and newspapers. She has a Master of Fine Arts in creative writing.