both times I have attempted to wash batting, have turned out badly. Actually, the one time, I just got the poly batting damp, tossed it in the dryer on "warm" to get the wrinkles and fold marks out (king sized packaged batting). That one ended up with sort of "crispy parts" which ended up trimming off and also had to make a dart like thing in the middle of it. Will not attempt to get the wrinkles out of a poly bat in the dryer again. The second time I found a mystery batting in my stash and decided to wash it gently and it went puff, disintegrated, little bits of fluff all over. Nope, not washing battings again. OK, now I mostly use batting on a roll, end of the wrinkled problems and shrinkage clearly indicated on the roll. I don't usually prewash fabric, and don't mind the small about of shrinkage my cotton/poly batting does. And the all poly batting doesn't shrink much at all. My recommendation is to know your batting and buy the one that shrinks or doesn't shrink to your liking.