I've had the same problem!! It was not Hobbs batting. I've never used either cotton batting or spray basting, with one exception, again! I now pin all my quilts. I just finished a small appliqued wall hanging that had to be spray basted, as the pins would have left too many wholes in it. I used bamboo/cotton blend batting. It didn't wrinkle or bunch but I still detest the spray basting! Too many other issues I can live without!