The cotton batting for vintage quilts was never prewashed. It would have fallen apart! These days it's possible to preshrink cotton batting -- because of needlepunching and surface bonding treatments -- but I'm not sure why someone would want to do this. For those who want a more modern "comforter" look, it's much easier to purchase polyester batting (which does not shrink) than to preshrink cotton batting (which typically shrinks about 3%).