Originally Posted by
mainaman
Are you sharpening western planes or Japanese?
As far as hardness one can't compare Jnat to C12k, coticule Escher or anything else but another Jnat, it is like comparing apples to oranges.
Your proposal of test by rubbing two stones will not work unless the slurries are different color because how will you be able to tell which slurry you are looking at? A more sensitive test will be to make a very light scratch on each stone and see which one will smooth faster, that stone will be the softer one.