Acrylic refers to a synthetic yarn that offers the wearer numerous advantages. The wool is easy to maintain, strong, durable and wears well. The only drawbacks of this type of material are that it doesn't offer a great deal of warmth and tends to pill if you don't wash it carefully. If you've received or inherited an acrylic hat that you love aside from the fact that it's too loose for your head, you can still shrink it to create a snugger fit.
Place the acrylic hat inside of a lingerie bag. If you don't have such an item a woman's stocking will do. Tie or snap the bag shut, or knot the stocking.
Put a large pot of water on the stove to boil over high heat. Use a pot that you don't plan on cooking food out of again. Once the water reaches a boil, lower it down to a simmer.
Place that hat in the hot water and dunk with a pair of tongs until you've properly submerged it. Allow it to simmer in the water for 40 minutes.
Stick your tongs in the water and remove it, placing it on a towel. Wrap the towel around the hat and soak up all the excess water.
Place the hat in the dryer on the highest heat setting. Once the dryer cycle is over, the hat will have shrunken properly and will be ready to wear.