First, I'd do a test as mentioned - a damp flour sack towel rubbed on the fabric. If the towel shows any color at all, then you know you have a bleeder. Fill a bucket or tub (depending on how much fabric you have) with hot water, add a drop of Dawn or other detergent, and soak the fabric for 12 hours. Drain, spin excess water out, dry, and you'll be good to go. You won't need color catchers.