Thread: Coticules: Hard or Soft?

Originally Posted by kevint

Reading all this I am still unsure why Ardenne's for example would suggest softer stones for razors.

I emailed SO about getting a Nakayama asagi for honing straight razors. He replied with a long email in which he described the variations of the stones. The gist of his email was asking me what I wanted to accomplish with the stone. He wanted to know if I wanted a fast cutter , a finisher up to 50K or something in between. I came to the conclusion that I didn't know the answer so I didn't buy anything. My guess would be that Rob figures that razor customers would want a hone that will show results more quickly rather then a hard and slower cutting finishing stone. I may be wrong but that is my supposition.

I like your logic, Jimmy. It's been said in this post that a superlative coticule for our purposes would be a "hard" coticule. I absolutely agree based on my experience in working with my coticules that a "hard" coticule and water puts a great polish on the bevels. However as with any hard stone that I own (coticule, Nakayama Asagi (yeah, I know there are supposed to be hard AND fast Nakayama stones, but I don't have one of those), Chinese 12k and a very fine slate stone) they....................polish.................... ........very...............sloooooooowly.

Medium coticules for me.

Chris L

A lone voice of dissent:

Yes, a too-soft coticule will produce slurry on its own, and slurry is not optimal for the final polish.

BUT a moderately soft coticule can be a wonder. With a very light slurry it can really 'reach down' and haul up an edge into keenness. Then you wash off the slurry and polish with very light strokes. Superb results.

In a series of superb coticule-related posts Bart has talked about the challenge of "chasing keenness." The challenge being that coticules can cut fast with a slurry, but the slurry dulls the edge, and then polishing with water only will take eons to put that grabby edge back on. The usual approach to the challenge is to go very gradually from light slurry to no slurry. I find this process very easy indeed with a moderately soft coticule. They are terrific keenness chasers in my experience.

My theory is that a moderately soft coticule is steadily revealing fresh garnets. If you're vigilant about not letting a slurry develop, you won't get that blunting effect and yet you can polish quickly.

Originally Posted by dylandog

A lone voice of dissent:

Yes, a too-soft coticule will produce slurry on its own, and slurry is not optimal for the final polish.

BUT a moderately soft coticule can be a wonder. With a very light slurry it can really 'reach down' and haul up an edge into keenness. Then you wash off the slurry and polish with very light strokes. Superb results.

In a series of superb coticule-related posts Bart has talked about the challenge of "chasing keenness." The challenge being that coticules can cut fast with a slurry, but the slurry dulls the edge, and then polishing with water only will take eons to put that grabby edge back on. The usual approach to the challenge is to go very gradually from light slurry to no slurry. I find this process very easy indeed with a moderately soft coticule. They are terrific keenness chasers in my experience.

My theory is that a moderately soft coticule is steadily revealing fresh garnets. If you're vigilant about not letting a slurry develop, you won't get that blunting effect and yet you can polish quickly.

"moderately soft" to me would be "medium", would you agree? If so, the ranks of dissention grow by one.

Chris L

Yes I guess so.

I've only ever had 5 or 6 coticules. The softest was my hands-down favorite and I sold off most of the others.

Until I read this thread I'd have just called it soft. Put it this way it took me about ten minutes to lap and chamfer. But you can't quite scratch it with a fingernail, and it doesn't quickly yield a slurry when you're honing with just water, so I guess it's not soft by this measure.

Coticule threads lately have emphasized their ability to cut bevels when you use heavy slurry, and their ability to polish but not cut when they're hard and used with just water. It's even been suggested that they're not very good for the in-between – i.e. that they're too slow to really sharpen effectively (as opposed to polish and smooth) with just water, and meanwhile slurry is dulling. I've even read about going to a different hone to get the edge back on, then polishing it on coticule without slurry.

All well and good, but for me this is where the "moderately soft" – okay, okay, medium – coticule really shines. This one is my main man. My most versatile hone. Any amount of dulling short of bevel re-creation and this thing makes short work of putting the edge back on. And with no slurry at all and very light passes it's a highly effective polisher. Perhaps a very hard coticule would be an even finer finisher, but I'm not yet convinced of this.

I would like someone who knows to tell us in what way the soft coticule differs from the hard one. Is it that the makeup of the rock is different or is it that the rock is just weathered and is starting to rot.

You would not want any sharpening stone so soft your fingernail could scratch it. That puts it in the league of talc or Gypsum. If you used a razor on that it would wear away rite quick.

Originally Posted by dylandog

Yes I guess so.

I've only ever had 5 or 6 coticules. The softest was my hands-down favorite and I sold off most of the others.

Until I read this thread I'd have just called it soft. Put it this way it took me about ten minutes to lap and chamfer. But you can't quite scratch it with a fingernail, and it doesn't quickly yield a slurry when you're honing with just water, so I guess it's not soft by this measure.

Coticule threads lately have emphasized their ability to cut bevels when you use heavy slurry, and their ability to polish but not cut when they're hard and used with just water. It's even been suggested that they're not very good for the in-between – i.e. that they're too slow to really sharpen effectively (as opposed to polish and smooth) with just water, and meanwhile slurry is dulling. I've even read about going to a different hone to get the edge back on, then polishing it on coticule without slurry.

All well and good, but for me this is where the "moderately soft" – okay, okay, medium – coticule really shines. This one is my main man. My most versatile hone. Any amount of dulling short of bevel re-creation and this thing makes short work of putting the edge back on. And with no slurry at all and very light passes it's a highly effective polisher. Perhaps a very hard coticule would be an even finer finisher, but I'm not yet convinced of this.

your description is very close to the feelings ( I have for my cot. But without 5 or 6 i couldn't classify it as hard or medium. If i got another that was not as good or better I would be quite disappointed.

I would guess that the relative hardness is a function of depth.

so far I've been relying on luck to bring me another but nothing so far...

Originally Posted by thebigspendur

I would like someone who knows to tell us in what way the soft coticule differs from the hard one. Is it that the makeup of the rock is different or is it that the rock is just weathered and is starting to rot.

You would not want any sharpening stone so soft your fingernail could scratch it. That puts it in the league of talc or Gypsum. If you used a razor on that it would wear away rite quick.

Just my impression but I think it must be the density of the binder ? The garnet will be uniformly of the same hardness ....wouldn't it ?