I pre-rinsein water as hot as I can stand. Except for backing--that actually goes into the washer with a very small amount of soap. I pre-rinsed 20 FQ's today and dried in a hot dryer. About half showed some colour in the water---not a lot but maybe enough that could have bled into the adjoining fabric in a quilt. My reasons as stated above--no nasty surprises---and I don't sneeze or wheeze when working with the fabric.