Shaptoneers, please confirm something for me...

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Originally Posted by Bart

Rating the coticule with slurry 6K to 8K is pure nonsense.

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First off: I haven't intended to offend you, I just wanted to share a differing experience.

Second: When I said "issues" I was making reference to your own claim that you find the coticule's behavior "enigmatic", nothing more.

And, I think you're misunderstanding what I meant about the abrasive action of the stone. I don't intend to actually rate the grit at any level other than what it is, what I mean is that the extra garnet content in the slurry cuts steel with a speed that is much faster than the usual "8k"coticule. So it is as if the coticule were a 6k when you form a slurry, not that the garnet cuts 6k sized scratches. And, in fact, this is the case when you raise a slurry on many abrasive stones, not unique to the coticule.

Your experiment is nice, it was thoughtful and well executed. But it is faulted by the previous misunderstanding, in that the grit size has stayed the same, so yes, they look very similar. What your pictures don't show is the amount of material each method took off of the edge, which is what I meant by the lower/higher grit ratings. If you get an old wedge or some other razor with a fat bevel I think you'll be able to see what I mean by the "hazy" look made by the slurry, and the "polished" look made by the plain wetted (I've heard the word somewhere, so I'm gonna run with it) surface.

As for the wide variance in performance characteristics among natural stones; I am well aware of it, to say the least. But it is much harder to describe to someone (usually new guys looking for "the best stone for the money that will do everything I need"), with no first hand knowledge of the subject, how the slurry cuts faster but is the same grit as the base stone, or how the stone can both set a bevel and give a fine polished edge. It's just easier to make an analogy to lower/higher grit ranges.

And sure there is documentation saying that garnet is a crystal that is an X rating on the MOHS scale, it is, on average, Y microns in diameter, with Z number of facets, and that the Coticule is comprised of between ALPHA and BETA percentages in concentration of garnet crystals. But unless you get your precise stone analyzed, your still just guessing at it's rating anyway. And when it comes down to being realistic, you just have to have a bunch of stones to compare performance characteristics and decide what kind of rating fits.

(Does anyone remember what happened to that project where there was a chart that compared the different characteristics of various stone to the Nortons and DMT's?)

Icedog,

Thank you very much for your reply. I like your pictures! I can see you enjoy the virtue of quality tools:). Actually the tomato cutting analogy was just a bad attempt to be funny, which is a flaw in my character. But your explanation of it makes sense to me, and the idea of looking at the "peaks" of the edge as spears that concentrate the cutting force in spike points to allow for better penetration is both new and revealing to me. I just finished cutting a tomato in the slowest possible motion, and I could actually see the serrations punching through the tomato skin, before the inclusions follow. The big question is: are similar principles at work when a razor slices hair? At least I can see one flaw in my previous reasoning: I assumed that one hair got trapped in one inclusion between to peaks, and that the sharp bottom of that inclusion did the cutting. How stupid could I be? A hair measures between 30 and 120 microns, while razor striations are about 10 times smaller. Thank you for showing me the light on that. The question of course remains: does "toothiness" really make a difference if applied to a razor's edge? And if so, what would be the ideal size/distribution of the teeth?
I am aware that shapton owners generally do not bother with such ideas, but just put the finest possible edge on a razor and shave while whistling Dixie. As for myself, I'd rather drop dead than slicing tomatoes with a serrated knife, and as far as a razor edge goes, except for the whistling, I have been following the "polish as far as possible" approach. I like to find out IF a "striated" approach to razor's edges makes equal, less or more sense.

Thanks again for chiming in.
I hope you make quick and full recovery,

Bart.

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Originally Posted by Russel Baldridge

First off: I haven't intended to offend you, I just wanted to share a differing experience.

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It is true that I felt a bit patronized by your reply. But I have a great appreciation for your knowledge about all things steel and sharp and your willingness to share with others. I think we have that in common, at least the willingness to share part.;)

My statement that rating the Coticule with slurry as 6000 grit is nonsense, was not directed to you. After all, you only mentioned others rating it that way. A coticule with slurry cuts at least 10X faster than one wiith water, and both you and I are not going to start rating it 600 grit, are we?:hmmm:

Thanks for thinking this thing through with me,
We have been quibbling before. I don't take that personal, and I hope neither do you.

Kind regards,
Bart.

Nope, no personal offense taken.

As for the striations; I think that, at the lower grit levels, the uneven portions of the edge that feel like teeth may be comparable in sharpness to the final desired shaving edge so they are what's making the blade appear to pass the HHT but in reality, the main cutting bevel is much too dull (not to mention that you'd have some serious razor burn from the teeth) to shave with. And when higher grit stones are used to remove the inconsistencies along the main cutting bevel, the sharp teeth are removed, leaving a slightly duller, but much smoother, razor edge.

This can be continued up as far as one wants to, or can realistically, go (i.e. shapton 30k, Nakayama, .25 diamond). And at some point, the edge just cannot get any finer. I have yet to tell a difference between CrO and my Nakayama because, at those grit levels, the striations are almost non-existent and it's the quality of the steel and the bevel angle that are the noticeable properties.

So, to summarize my attempt to answer your question, I am saying it's possible that the teeth are sharper than the main bevel, sharp enough to pass the HHT, and that a polished razor edge returns to the same (or finer) sharpness of the original teeth but without the serration. Thus making the edge "shave ready".

Is that somewhat in line with your observations?

Russel,

What you describe is what I believe to be the foundation of "the progressive honing method". From the very beginning it always made the most physical sense to me, so I have learned to hone my razors by those rules and still am to this day. My edges shave well and last between 10 and 20 shaves before I need to touch up. Many people would be happy with that and never give the bare physics of honing another tought. But that's not me...

There's the pyramids. No doubt in my mind they result in fine shaveready edges, but I can't honestly believe that 5 laps at 8K can remove 1 lap of scratches at 4K. I could be wrong, having no experience with Nortons and all. The last thing I want is this thread gliding off to yet another "progressive" versus "pyramid" discussion, so I 'm not going to say anything more about that.

But I have another observation: Robert Chevalier, owner of a razor store in Antwerp, tutors shaving and honing classes. As I mentioned in previous posts, his method really works, and because of the success of his courses, there are probably more people in Belgium that hone with Chevalier's paradigm than those who follow one of the methods advocated on SRP. Chevalier does this:
He raises a good slurry on a coticule. Then he hones, usually without X-stroke, a number of laps on the coticule, till the TNT passes. Next he runs the razor over a piece of horn that he keeps in water. It smells awful, and I really think it is not needed, but he states they do the same at Dovo, and it serves to remove a possible burr. As a final honing step, he does a few very light laps on a pasted paddle strop, cured with red Dovo paste (that's 4 (edit) micron!, if I'm not mistaken). He doesn't do much, just enough till the razor passes the HHT. (Is he pulling some teeth out of that finely polished coticule edge??) Then he strops about 20 on canvas and a bit more on clean leather. That's it.

I saw him do it. I saw his wife do it. I have tested a razor honed by her, that I knew for sure to be dull prior to the honing (a heirloom piece that had been lying in a drawer for 30 years). It passed the HHT very well. My friend learned to shave with that razor, and it stayed keen for many shaves.

All that leads me to wonder if there might be two types of edges. The one I have on my razors as we speak, which corresponds with what you describe in your mail, and another type of edge that includes "teeth".
The first thing I need to know to answer that question, is whether "teeth" really makes a difference for cutting a hair, hence the Shapton experiment I called for. I really hope there are people willing to perform the experiment (polishing an edge with a progression of Shapton hones and performing the HHT after each hone), and start posting their results any time soon.

Bart.

I think you're on to the right explanation. The coticules have garnets in them and it's the corners of the rhombic dodecahedral shape that get cleaved from the embedded crystal and make the slurry do the cutting and polishing of the edge. The eschers have silica in them. Different crystal system - hexagonal, long C axis, equal A and B axes. The result is different and it can be seen on the steel at the end of the process. The diamonds in a diamond stone are different yet again both in crystalline family (cubic) as well as in use. The nickel plating holds the diamond in place while the steel is abraded over it. That is very different from slurry honing and the results are different. Check out the difference in coticules when the edge is dry honed vs. slurry honed. Tim Zowada has photos of the two methods result on straight razor edges. The dry honed is brighter but doesn't shave as well.

Coticule rated as a 6000? What's THAT about? I've been honing razors for years on coticules and have customers around the world who have been doing so as well. Their consensus is the coticule (Select grade) is rated as an 8k but polishes an edge to about a 10k. The belgian blue is similar. It is rated as a 4k but polishes toa 6k. You do have to use a slurry as the Belgians (and I) recommend. A pure coticule slurry stone ("cotigura"), a word I invented, is the best slurry stone to use either with coticules or belgian blues.

Hey Howard,

Nice info, thanks for contributing. Yes I saw Zowada's photos. I tried dry honing, but did not liked the results as much.
Another thing I have been trying, is to backhone on slurry after setting the bevel on a DMT, and then finish with a normal stroke on water. The results were very good, but I 'd have to build more experience with that approach and compare it to my regular honing paradigm, before I could confirm if there's any real advantage.

Is there really no one willing to do the initial experiment?
(honing a razor with a progression on all the Shapton hones and performing an HHT at each stage).

:(

Thanks to everyone for sharing his viewpoints on this one.
Although there is no final outcome, I still learned a few things.

Kind regards,
Bart.