I used the method that Peckish posted and quite a bit of dye came out. I then washed it again and the water was quite clear, so it looks like a success. I dried the fabric...I was afraid it would be faded after all that... but it still looks black.
GeriB, good question about what the manufacturers are doing, and why clothing doesn't bleed like this. This was good quality fabric.
Thanks again to the QuiltingBoard for coming to my rescue.
Watson