Originally Posted by
roughkype
Where did you find that rubstone? It goes with a very good barber's hone, the Frictionite. It's intended to deglaze the Frictionite. I don't know what sort of grit it would leave if used as a slurry stone; could leave something far coarser than you want. Back when I honed reed knives on my Frictionite, I used the rubstone quite a lot. I'd say it's too soft for lapping--mine thinned down pretty quickly.
If you could find the barber's hone this was paired with you'd be in good luck. Probably out a pretty penny too.
To flatten your hones, use some 300-grit wet/dry sandpaper on a marble tile, or treat yourself to a 325-grit DMT plate. The DMT plate is also the standard tool for raising slurry if you don't have a slurry stone for your hone.
Normally, the slurry stone is just a small piece of the same stone as the hone itself. Nagura stones might be os are a different source, but they're a special case. DMTs are nice neutral slurry-raisers, because they do not shed any grit onto the source stone.