Wool and other animal fibers make cozy garments that keep you warm all winter, but they require special care. The scales in wool are much like the scales in human hair, and just as your hair can form knots with enough friction, wool can shrink. This shrinkage, called felting, occurs when wool is exposed to hot water and agitation. If you accidentally toss a wool garment into the washing machine, it's possible to stretch it out again with a process called blocking.
Fill a clean sink with cold water and add 2 tablespoons of hair conditioner or baby shampoo. Swish the water gently to mix in the shampoo or conditioner without making suds.
Place the shrunken wool item in the water and allow it to soak for 30 minutes.
Remove the item from the sink and gently squeeze out as much water as you can, without twisting or wringing. Lay a large bath towel on the floor, lay the item on the bath towel, and roll the towel from one end to the other to absorb the rest of the excess water.
Lay another dry towel over a large piece of thick cardboard -- a flattened cardboard box works well. Place the item on the box and tug it gently to stretch it back into shape.
Pin all the way around the edges of item with straight pins, sticking them through the sweater, through the towel and into the cardboard. Place one approximately every 2 inches to hold the item in the shape into which you have stretched it.
Allow the item to dry thoroughly before unpinning it. If it is very large or thick, this can take up to two days, depending on climate. To speed up drying, place it in front of a fan or dry it outdoors in the shade on a warm day.