I was thinking about getting some connecting threads batik charm packs to make a quick quilt. All the cutting already done has it's appeal. My question is how color fast would they be? I don't think prewashing 5x5 squares would be practicle but I don't want a bleeding mess after I put it all together. I'm figuring if none are prewashed they'll all shrink about the same so that should be okay. Most concerned with the color bleed. Anyone have any experience with these?