I have seen some hard Arks let loose a little bit of auto-slurry but only right after lapping, and only for a very short time. It seems to me that it's usually the white translucent ones that it's been more common with. In my experience, with those few that do, after that first little bit they don't release much of anything.
That black Ark staying dull like it is makes me think it's not getting quite to the level of burnish that it needs for the best razor edges.
Here's about where I like mine to be. Both shots are my NW 3" x 10" Translucent black Ark with the stone dry and washed with acetone - no oil or water on the surface. Second shot is a near 90° reflection of an incandescent light bulb, you can see it pretty clearly.
That black Ark staying dull like it is makes me think it's not getting quite to the level of burnish that it needs for the best razor edges.
Here's about where I like mine to be. Both shots are my NW 3" x 10" Translucent black Ark with the stone dry and washed with acetone - no oil or water on the surface. Second shot is a near 90° reflection of an incandescent light bulb, you can see it pretty clearly.