I use Warm and White cotton batting and always preshrink it. I put it in very warm water in my large utility room sink and let it soak 30 minutes to an hour (depending on if I forget about it or not!). Then let it drain, squish out excess water so I can pick it up and put it in the washer for a delicate spin only cycle. Transfer it to the dryer and run on low heat delicate cycle again. Pull it out promptly and fold it up till I need it. Works great.