Thread: About Blues and Yellows

For the better part of the past year, I 've been honing with nothing more than one DMT 1200, 3 Belgian Blues and a small collection of Coticules. I have conducted many comparative tests.
So far I have not thoroughly rounded up my conclusions so far, in one post. Maybe it's time I did.

I found no real variance between the Blues, they all behave very closely the same.
This is not so with Coticules. They show significant variance when used with slurry, but differences practically dissipate when they're used with water.

With slurry all coticules level off at a certain keenness that is only barely shaveable.
When this level is reached, diluting the slurry every 10 laps with 2 drops of water till eventually all slurry is washed away over the course of 70 to 100 laps, dramatically improves the keeness, but the final outcome is a bit unpredictable.

The Belgian Blue with slurry is in absolute terms much slower than the coticule.
The Belgian Blue with slurry also levels off at a certain keenness, but this keenness is sharper than that left by the coticule with slurry.
The diluting trick on the Blue works too, but to a lesser degree than on the Coticule.
The Blue with water only does hardly anything on hard razor's steel.

A Coticule, when used with water as a polisher/finisher, smooths out almost any edge, also those that are sharper than what can be achieved with the Coticule by itself. It will not refine the edge as such, only smooth out the previous scratch pattern and leave it there.

With a heavy slurry, a good coticule can easily do the work of a DMT-1200 for honing out small edge defects, at the cost of some rounding at the bevel tip. For all other use on razors the slurry must be kept thin. Slurry on the Blue must also be kept thin.

Controversial, but I stand by it: Belgian hones don't lend their unique properties form a very fine grit rate. They are unrivaled because they leave such shallow scratch patterns, left by their round honing garnets that create a wavy surface. As a result the edge is far less jagged than that of many synthetic hones. This also means that the edge of the Blue with its larger garnets is even less jagged than that of the Coticule, a capacity that explains the higher level of keeness left by the Blue with slurry than that left by the Coticule with slurry. I will elaborate on that in a thread I plan on posting next week.

Bart.

I really like your systematic approach to using these stones. Thanks for doing the experiments and posting your results.

Hey, super post.

I have a question about the following:

Originally Posted by Bart

A Coticule, when used with water as a polisher/finisher, smooths out almost any edge, also those that are sharper than what can be achieved with the Coticule by itself. It will not refine the edge as such, only smooth out the previous scratch pattern and leave it there.

I'm reading this to mean that say, even a .5 diamond edge or a Shapton 16K edge could be further smoothed with a coticule without any loss of that extra sharpness these media provide. I just want to clarify that that's what you're saying, because your first sentence makes it sound like your experiments have been conducted without anything higher grit than a coticule...

Not a gotcha thing just trying to make sure I've understood.

Also, regarding this part –

Originally Posted by Bart

With a heavy slurry, a good coticule can easily do the work of a DMT-1200 for honing out small edge defects, at the cost of some rounding at the bevel tip.

Do you mean it rivals the speed of a DMT? How big are the chips you're removing with a coticule w/heavy slurry? Do you ever tackle standard ebay-razor-type corrosion with a coticule?

Thanks for all this experimentation and the superb write-up Bart.

«A Coticule, when used with water as a polisher/finisher, smooths out almost any edge, also those that are sharper than what can be achieved with the Coticule by itself. It will not refine the edge as such, only smooth out the previous scratch pattern and leave it there.»
I'm reading this to mean that say, even a .5 diamond edge or a Shapton 16K edge could be further smoothed with a coticule without any loss of that extra sharpness these media provide. I just want to clarify that that's what you're saying, because your first sentence makes it sound like your experiments have been conducted without anything higher grit than a coticule...
Improving a .5 diamond edge with a coticule? I don't think so. After an abrasive stropping, due to the cushion effect of a strop, those edges become a bit convexed at the tip, which renders it out of reach for a hone that only polishes (such as the Coticule with water). As for the Shapton 16K edge, Captain Zero does it, so he's the expert to shed some light on this.
I think depending on how many laps you do, you 'd pay the extra smoothness with a minimal loss of some keenness. About a week ago, I honed an Eclipse razor, nearly a wedge. The initial progression was: Coticule with heavy slurry till it passed the TNT, next the DMT 1200 till it popped hairs, next Naniwa Chosera 5K with inspection under magnification till the DMT scratches were gone, and finaly the Chosera 10K also with visual inspection. The shaves were outstanding, but the combination of such a heavy blade (big momentum) and the ultra sharp edge from that progression, caused tiny bleeding spots on my skin. After two shaves I performed a conservative 15 light laps on a coticule with water. My face likes the edge better now, but the razor shaves just as effortlessly. I suspect the Naniwa edge might be "toothier" which makes it more demanding for a precise shaving angle. Of course, my shaving technique being tuned in with coticule edges, might make all this a nice self-fulfilling prophecy. But even so, the coticule finished edge off the Naniwa is unquestionably keener than a coticule finished edge off a Belgian Blue.

Not a gotcha thing just trying to make sure I've understood.

I like to address honing with a scientific approach. Peer review and critical questions are always more than welcome in that respect.

«With a heavy slurry, a good coticule can easily do the work of a DMT-1200 for honing out small edge defects, at the cost of some rounding at the bevel tip. »
Do you mean it rivals the speed of a DMT? How big are the chips you're removing with a coticule w/heavy slurry? Do you ever tackle standard ebay-razor-type corrosion with a coticule?

Yes, my fastest coticule rivals the speed of my DMT 1200. In fact I prefer that coticule over the DMT. It's more pleasant in use. But I always finish bevel work with honing on the DMT till I can pop hanging hairs along the entire edge.

How big a chip? Anything that asks for very close inspection, or magnification, to be visible. If it's bigger than that I go to a DMT 600 or even to a 325.

About ebay-razor-type corrosion. Maybe this will sound like blasphemy, but I always remove a small portion of the bevel after I finish restoring a razor. I grew tired of waisting my time putting an edge on steel that turned out to be unreliable ("cheese-with-holes"-syndrome, edges prematurely crumbling away, bad durability). Doing that clearly calls for coarser hones. If an old razor doesn't need restoring, but merely shows some surface corrosion on the edge, sure, I'll saddle my Coticule workhorse with some slurry and hone away.


Thanks for the appreciation,
Bart.

Nice post. Help me out here. From what I read, I'm assuming that if you had a natural combo you would use the yellow coticule (maybe with slurry) first and follow it with the blue. Is that correct?

Originally Posted by kelbro

Nice post. Help me out here. From what I read, I'm assuming that if you had a natural combo you would use the yellow coticule (maybe with slurry) first and follow it with the blue. Is that correct?

You have that backwards. Blue with slurry, then yellow (with slurry if you want, then water) is the typical progression.

That is typical, Joke, but if Bart is going from the coticule with slurry TO the DMT 1200, then that means that he feels the Coticule with slurry is faster than the DMT, which is pretty dang atypical. Plus, he was asked explicitly about this, and confirmed it in a few posts previous.

Recall that he went Coticule w/ slurry --> DMT 1200 --> Naniwa 5000 --> Naniwa 10000 --> Coticule w/ plain water

Originally Posted by joke1176

You have that backwards. Blue with slurry, then yellow (with slurry if you want, then water) is the typical progression.

Exactly my point. That's how I do it. But my take on his post is the opposite.

Bart, very useful post! I enjoyed reading it!

I'm going to add the following website to this topic : Zowada Custom Knives - Stone Surfaces

Hi-res pictures of the bevels and edges of razors made after honing on different types of whetstones.

Please don't forget to click on the links at the bottom of the page!!!

Originally Posted by Bart

The Belgian Blue with slurry is in absolute terms much slower than the coticule.
The Belgian Blue with slurry also levels off at a certain keenness, but this keenness is sharper than that left by the coticule with slurry.
The diluting trick on the Blue works too, but to a lesser degree than on the Coticule.
The Blue with water only does hardly anything on hard razor's steel.

Bart.

He is neither saying to go from the blue to the coticule or from the coticule to the blue, at least not in such simple terms.

Here is the evaluation, as I see it.

According to the second sentence, the coticule with slurry is less keen than a blue with slurry. So, in terms of keenness, the following applies:

(1) (Coticule w/ slurry) < (Blue w/ slurry)

From a previous post, we find that he finishes with the coticule with water, even after such fine stones as the Naniwa 10000. So we can assume that the coticule with water is more keen than the blue with slurry, as follows:

(2) (Blue w/ slurry) < (Coticule w/ water)


Combining (1) and (2) we get this:

(3) (Coticule w/ slurry) < (Belgian Blue w/ slurry) < (Coticule w/ water)

Other stones may be in his progression, this is only a comparison of the uses of a yellow coticule and a belgian blue.

Also, due to the shallowness of the scratches left by the yellow coticule when used with water only, it can serve to smoothen out the edge left by most stones, even stones that are technically rated at a higher grit than the coticule, much the same way that many here use chromium oxde to smoothen out hte edge left by .25 micron diamond compound.


I'm not saying this is my personal take on how the honing progression should go with the belgian stones, I'm just trying to clear up the confusion as to what Bart said. I haven't used a coticule nearly as much as he apparently has, so I defer to his expertise in these matters.

Also, according to Bart, using a Belgian Blue with water only is so slow when used on a razor that it is rendered basically useless, so it's not in his honing progression.

Bart, please don't feel like I'm trying to put words in your mouth, I was just trying to eliminate confusion. If I was wrong on any of these points, please feel free to correct me!