Pre-wash like the above posters advised. Probably at least 1/2 of them bleed - some are horrible to get to stop bleeding. I just swished mine very gently in my pure white dishpan with a drop or two of liquid soap in lukewarm water and then rinsed in cool water. If they did not bleed, then I rolled them up in big thirsty towels and line dried - did not bother to iron then. Not much wrinkling that way. Some never did stop bleeding so threw at least two pieces away. The dark blues are the worse ones to bleed.
I got a beautiful black and gold piece of batik from a lady on here and it did not appear to have been washed, so I proceeded to wash it the minute that I got it and the color of the water was tea colored. Not too dark. I then emailed her and told her that the fabric arrived here in the mail and that I had already washed it and that it did not bleed too much - she was surprised, because she had prewashed it.