Originally Posted by
Luke Dupont
Is micron a measure of height variation, or width variation? Does it assume that height and width are equal when discussing "particle size"? You can have particles spread further apart with less differentiation between peaks and vallies, and you can also have particles that wear and become duller and rounder as opposed to remaining sharp and pointy. And in the case of Arks, you have particles that are so tightly fused together that you have something of a more solid surface with pores rather than extruding bumps / crystals.
There are a ton of variables that go into it which some measure of "particle size" doesn't capture, I think. The shape of the particles, the way that they wear or don't wear (how sharp or rounded they become) and the nature of the surface (pores versus protruding particles, and how even or far apart they are spread), as well as things like friability or lack thereof (Jnats and waterstones, for example, with their abrasive particles that are suspended in a slurry).
All these factors and many more produce different sorts of cutting actions, and impart different edges. I'd love to know, too, if anyone has a measure of all these different factors and can explain how they work.
It's also worth noting that difference in the hardness of the stone versus the steel affect the finished edge as well. Sharpen an O1 tool on an Ark, and then Japanese steel, and then A2, and you will find different results and cutting action on each one. The O1 chisel will have a slightly coarser edge than the Japanese chisel, which because of the narrow hardness gap between the steel and the stone, will be more polished and burnished on the Arkansas stone, making a Soft Ark cut produce a finish somewhat finer and closer to a Hard Ark.
If the difference in hardness is further apart, you will get less polishing and more grinding - you will cut quicker but coarser. Sharpen those three steel types on diamonds and you will notice very little difference in the finished edge.