Quote Originally Posted by zib View Post
Slurries just increase speed, not the size of the grit. IMHO.
This much is certainly true, as to state otherwise would be a physical impossibility.
However, use of a slurry with a coticule definately does reduce the sharpness of the edge (Probably why it was quite confusingly said to act like a lower grit hone). This is thought to be due to the edge colliding head on with the garnets in the slurry.
The reverse seems to be true for Japanese naturals. Use of a slurry with these stones seems to have the ability to impart a sharper edge, but I don't know a lot about these hones.

So while the use of slurry does generally increase speed it also has an effect on the sharpness of the edge which can be attained with that particular hone.