I prewash all fabrics to withstand all types of treatment. Since a lot of the quilts I make are wheelchair quilts for our local nursing home, the fabrics are usually prewashed on hot like they will be washed there. They requested STURDY quilts because of the frequent harsh washing. Some people have donated quilts that are not prewashed, loosely quilted, tied, or not quilted at all and they do not survive the constant washing and abuse they get. I prewash the flannel backings twice because of the increased shrinkage and then wash the finished quilts before they are donated. Have not used wide backing yet, but definately will handle that as I do flannel after seeing these comments.