Thread: Estimating bbw/coticule grits

If a piece of abrasive is 10 microns in diameter, but protrudes from the stone 6 microns or less does it polish like a 8 micron abrasive protruding the same distance? How about a football shaped piece of garnet protruding point up vs side up? Micron rating doesn't always translate well to grit rating as grit rating doesn't translate well in natural stones.

Originally Posted by ezpz

can anyone describe what they mean by inclusions in coticules? are these hard inclusions that damage an edge? or are these variations within the mineral matrix surrounding the garnets which give it different colour without a significant difference in honing properties? i have the feeling that some standard coticules are simply coloured something other than solid yellow.

I'm unclear on this as well hence my somewhat confused post above. I've been using vintage coticules, the more suitable (for razors) of them, all have what I'd call inclusions ie manganese lines, and none of which have a totally uniform colour. Would this mean that they would not be select today? I'm not trying to grind any axe here (so to speak) but I am puzzled. Kind of think that I've either got to luck into a pure vintage or bite the bullet and buy a select stone new.

As regards the 4k/8k distinction, while the latter kind of works if you think of it with a standard deviation attached (+/-2k or more), the 4k BBW attribution seems more random than anything. One of the entertaining (or frustrating, delete as applicable) things about coticules is the way that you can get them to function over an often wide range of putative grits.

I honestly think the 4k/8k "rating" that was applied to the BBW and Coti was simply a parallel to the Norton 4k/8k, which was THE hone back then.

As we know, grit size doesn't tell you anything about how a hone will cut a razor, nor does it tell you what the edge will shave like. As a corollary, you cannot shave with a razor that was finished on a hone and say what the grit rating of that hone was; you can only compare the way the razor shaves with the way a razor finished on another hone shaves. I myself am guilty of using a "shave off" to "estimate" the grit of a hone, but it is really just comparing the way an edge off one hone shaves compared to the way an edge of another hone (of known grit or not, it doesn't matter) shaves.

In summary, it doesn't matter what grit a hone is; all that matters is how it cuts and what kind of edge it leaves.

Originally Posted by Disburden

Bingo.

To my thinking, which may be wrong, I can't see how having inclusions on a stone which are peering through the surface at me are just going to change the appearance of the stone.

I would think it would be unlikely but possible. If you view it like synthetic stones that have a abrasive and a binder, you could change the color of the binder with out effective the abrasives. Conceivably at least, I would be surprised if the colors of say Norton's are not just for cosmetic and identification purposes and you could conceivably get a non uniform color on a uniform stone.