I always at least pre-rinse fabrics to get the chemicals out and put them into the dryer to pre-shrink. If it is a red or a fabric I think will run, I place it into warm water, let it soak for 24 hours and keep changing the water until it stops running. Sometimes it is up to a week before all the excess dye is gone, then I do the vinegar trick to make sure it is set and let it soak again in warm water to make sure it will not bleed. Only then do I feel safe using the fabric.