Coticule Break-In?

[Koop]

I've used my coticule several times, always with the same slurry stone. Last time I tried an experiment. I tested the edge of the razor on a packing peanut after honing on a King Gold 8K, then honed with a creamy slurry on the coticule. Re-tested on the packing peanut and the edge took a step backwards. After trying a few iterations I found a light skim milk slurry brought the edge forward.

Okay, so today I was repairing an edge on an old Shumate (they're all old, right?). After the 8K King, I went to the coticule with the skim milk slurry that my test indicated would be a step forward. Oh man, after ten laps the slurry was turning gray - this never happened before. My coticule seems more aggressive than ever. I wonder what changed? Do coticules break-in? I haven't honed on this stone all that much, maybe 8 - 10 times.

 

[sexy beast]

Try without a slurry. I use just water or soap and water 30 to 50 strokes. Then I use running water "small stream'' until I start feel resistance. Sometimes I do 30 to 50 strokes before I'm done. Every stone is different but generally the same with my two coticules. I have an Old Rock 5''x1'' and newly mined 8''x2''. This method works for me if the bevel is set properly.

 

[Legion]

One razor might have softer steel than the other.

 

[Koop]

One razor might have softer steel than the other.

Doh! This razor was an antique shop find with some chips and roughness on the edge. Now that I think of it, it responded fairly quickly throughout the stone progression. Talk about overlooking the obvious! Thanks for pointing this out.

 

[natto]

This razor was an antique shop find with some chips and roughness on the edge.

after ten laps the slurry was turning gray

That is pretty common (to me), with knives that have never been sharpened on flat stones. Some spines have a funny shape. Or the shape of the edge doesn't fit to the spine. I think of "high spots" that get more pressure and fast wear.

Once the geometrie is full developed, the phenomen diminishes. I would like to hear wether you can observe the same.

 

[Frank Shaves]

I doubt it. Coticule slurry is tricky.

 

[SliceOfLife]

I've used my coticule several times, always with the same slurry stone. Last time I tried an experiment. I tested the edge of the razor on a packing peanut after honing on a King Gold 8K, then honed with a creamy slurry on the coticule. Re-tested on the packing peanut and the edge took a step backwards. After trying a few iterations I found a light skim milk slurry brought the edge forward.

Okay, so today I was repairing an edge on an old Shumate (they're all old, right?). After the 8K King, I went to the coticule with the skim milk slurry that my test indicated would be a step forward. Oh man, after ten laps the slurry was turning gray - this never happened before. My coticule seems more aggressive than ever. I wonder what changed? Do coticules break-in? I haven't honed on this stone all that much, maybe 8 - 10 times.

They can... Especially hard coticules.

Basically the less a stone "Autoslurries" (To steal the old Rating Bart used 20 years ago)... the more chance it has to "Break in".

You can debate what this break in is. Is it garnets rounding off? Is it garnets breaking down to smaller pieces? Is it just the larger garnets being the first to break free of the surface and wash away?

Whatever is happening, on harder stones you are often going to see more aggression after recently raising a slurry or especially after aggressively lapping the stone vs after years of use without "agitating" the surface.


However what you describe seems more related to the razor than the stone.

On finishers... especially good ones with a wide range... if the razor is almost finished... they will be very slow. No swarf raised... they're just polishing a nice clean bevel.

Take that same stone, same razor, same technique... but you cut a fresh 1k (or 8k or whatever is "coarse" for you) edge into it... they raise a TON of slurry.

This is because the stone works... and the first time you gave it a razor that DIDN'T have a lot of wild metal topography sticking out in every which way for the abrasives to grab a hold of. The second time you did. So the first time it's removing very little... the second time you're putting it to work and it's removing a lot.


TLDR: The swarf on a finisher is usually more indicative of how close to finished the razor was when you went to the finisher than the state of the finisher.


What can screw with this reading is razors honed poorly (no bevel/bad bevel)... but polished highly. Not many finishers will pull heavy swarf off a razor in that state... gets back to the old way people would call hones "polishing" instead of "sharpening" past a certain level of fineness. Basically very fine stones will struggle to reshape a polished bevel/edge... but are much better at polishing a well shaped but rough-surfaced bevel/edge.


Of course softer steel can also explain it, like suggested above. I don't hone Kamisori's, but I did once... and every stone pulled crazy amounts of swarf off one of the two sides of the Kamisori. I mentioned this in a thread asking for help and the Kami guys pointed out that one side the spine isn't hardened (or mine had worn through the hardened part or something, can't remember)... so yes, steel hardness affects how fast you'll see swarf accumulate.

 

[Koop]

I would categorize my coticule as "hard." It doesn't self-slurry and when I raise a slurry on it, I suspect it mostly comes from my coticule slurry stone.

 

[Gamma]

Color of slurry is not necessarily an accurate or even useable indicator of speed or a greater/lesser amount of metal being removed at a faster or slower rate. I try to avoid judging the action based on color. If I need to, I can check the striations to see if they are markedly deeper, or not, and go from there.

The shade of slurry can vary due to a few different things. Whether or not the steel particles are staying in suspension or not, for example. Slurry density affects this, along with some other things, ionization, covalent bonds, etc.

Steel type, softness, hardness, steel particle shape, etc, all can factor in. If the slurry is a bit more aerated, slurry appearance can change too. If the edge was even so very slightly more toothy to start off, than the previous blade, there may have more steel in the slurry as a result. Tiny differences can have a very large impact on appearance. Lighting too, can affect appearance.

I stick with harder Coticules. I lap them regularly.
When I lap a Coti, it's usually on a 300x-400x worn diamond plate.
After leveling, I usually dress the working surface down with a slurry stone and then hone. I might finish lap on 600x w/d if it is handy.
Have not experienced significant behavioral changes with a fresh surface prepared that way.
If I had an old dirty stone that was loaded with swarf and build up, and I lapped it, then it might seem different after being refreshed. Maybe. My diamond plates cut better after cleaning too, sometimes.

If I lapped a Coticule with a new 140x plate and honed on that raw surface without any dressing, I suspect I'd see some changes until the top leveled out. That's pretty much the same for most stones though.

Making slurry on a stone will normally refresh the surface and allow access to fresh abrasive, Jnats are similar. Theoretically it would perform the same as the last time it was slurried though.

 

[blancpain]

On the topic of dressing coticules and using slurry - does creating slurry effectively change the dressing?

Say I've dressed up to 600x grit on w/d and then I use a slurry stone (which itself is lapped on a 325 DMT let's say) - is the dressing preserved or am I altering it with the slurry stone? If we are altering it what's the point of dressing coticules at all if we will be using slurry?

 

[Wid]

On the topic of dressing coticules and using slurry - does creating slurry effectively change the dressing?

Say I've dressed up to 600x grit on w/d and then I use a slurry stone (which itself is lapped on a 325 DMT let's say) - is the dressing preserved or am I altering it with the slurry stone? If we are altering it what's the point of dressing coticules at all if we will be using slurry?

I use a slurry stone to dress the stone after lapping So I can’t see it changing anything when ya slurry it.

 

[LJS]

I only use coticules for finishers really. Don’t see much point in all the slurry use and discussions for that purpose.

Instead of break-in, I prefer a glaze or burnish on an old and very hard coticule.

 

[SliceOfLife]

I'll probably do a dilucot once every few years just to prove I can still do it, but yeah, long run? Hones are cheap. Great finishers are valuable. Don't put wear on a great finishing Coti forcing it to do a mediocre job of low grit honing when you can buy a low grit hone, use the coticule to finish and have it last forever. That's my opinion anyway.

That's not to say a coti won't still last your lifetime doing dilucot, a thick layered, hard coti might... but folks have coti's from the 18th, 17th maybe earlier centuries... It won't last THAT long doing dilucot.

Same reason I never use a great razor finisher (except hard arks because they are unkillable by anyone who isn't a watchmaker*) with knives or other tools. Don't care how great the edge is... not worth putting the wear/dishing on a stone that with a razor is basically a permanent solution and will never show wear if ya stick to razor touchups.

I'm no Norton Razor Hone fan, but if ya are... Imagine how many Norton Razor Hones would be around today if the axe-men weren't burning through em for the past half century or more?


*If you wanna have your mind blown, buy a watchmakers kit with an old translucent ark in it... Those guys WEAR OUT arks, polishing whatever little tiny things it is they polish.

 

[Wid]

I doubt anyone would be wearing out coticule while honing a razor in any form or fashion. Might as well use them the way you want. I’m a fan of diluticot and do it frequently. There are a few old boat shaped stones I use as pure finishers but not for fear of wearing them out.

 

[JPO]

Even if i only used one coticule to hone all my razors i don't think i would be able to wear out any of my coticules.
I always had better results if I did a proper slurry dilution.

 

[Eshebert]

If I use a synthetic with a coticule at all, its for a correction (chip or geometry). Its Dilucot for me, but we all have our preferences. If you like it, I love it.

 

[Wid]

Even if i only used one coticule to hone all my razors i don't think i would be able to wear out any of my coticules.
I always had better results if I did a proper slurry dilution.

Same here