I snip off a corner and hand wash in hot water with the detergent I would use for machine was. Swish the swatch around until well saturated, then lay on white paper towel. If it's going to bleed you will see it on the towel. I have had reds with no bleeding. But the worst case was a turquoise. I hade to wash that one twice! I also swear by color catchers. Love sewing on batiks!