I prewash all my fabric and when a quilt needs to be washed I use shampoo I red this in a quilting book.I do not let the machine agitate but let it soak for 15 min and then send it into the rinse again let it soak 5 min and spin out I then place it on my clothes line lining side out. None of this was my idea but it certainly has preserved my king sized quilts. I do think that the agitation is hard on the fabric and quilting.