I also pre-wash in hot water. To hopefully control bleeding and shrinkage. If I am concerned, about bleeding, I use Retayne, and let soak in hot water for about 1/2 hour, then finish washing. I don't always use soap. I just washed a wide 108 inch backing in hot water and after washing and drying, it was 102 inches in width. A good reason to pre-wash to me.