I bought some black fabric from my local quilt shop. Since I planned to use it to frame off-white pieces, I pre-washed and used 3 color catchers, which came out pitch black. I washed 3 more times with color catchers before they came out light grey. I think it depends on what you're putting it with. If i were putting it with very dark colors, I would still pre-wash, but be less obsessive about it, but I think you need to be cautious with black.