I have found black Kona always bleeds but so do some colors. I made a quilt for our DGD of rainbow batiks with a white background. It was a jelly roll so could not pre-wash so I used Sythrapol and then Color Catchers. The only color the Color Catchers picked up was LIME GREEN, not magenta or dark purple or hot pink, but lime green. I was shocked. There was no bleeding on the white however. Always best to prepare for the worst bleed and be pleasantly surprised if there is none.