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First JNat Honing Experience

So I picked up an Ozuku Suita Koppa Katakuchi (see pic) from a knife and razor dealer I've purchased a few SRs from and they aren't the most knowledgeable about JNats, but they were told by the supplier (Imanishi) that this is suitable as an SR finisher so I decided to give it a try. I've heard that suita aren't normally hard enough to finish so I'm ok if this is a fast cutter that I can use as a pre-finisher in any event. I decided to hone a GD that I had previously honed with a black Ark finish, and gave me some excellent shaves, so this will give me a good comparison.

ozuku-koppa-katakuchi-1_5000x.png


I also purchased a tomo nagura and decided to hone the blade up to an 8K Shapton finish before moving to the Ozuku. I started with a thick slurry and tried to feel for when the slurry broke down and slowly added water till I felt the slurry was no longer working effectively. I then added a medium slurry and repeated the process adding back a light slurry and then water alone. I did around 200 passes in total and noticed a hazy finish to the edge, which I think is normal for this type of stone. I then finished using the stone under running water and noticed that the edge became more of a mirrored finish.

Tests seemed to show a fairly sharp edge and when I shaved with it today I noticed that it was somewhere between my Black Shadow and black Ark finish, which I was very pleased with. The edge is not as smooth as with the BS but no crisper than the Ark, so it's not as smooth as I would like, but I've also heard that JNats tend to produce a crisper edge than slates so this wasn't unexpected.

Overall, I'm very happy with my first experience with this stone and hoping that I can take the edge further, and maybe get a little more smoothness as well, as I learn my way around this stone. I can certainly see why JNats are so popular!
 

Steve56

Ask me about shaving naked!
That doesn’t look like a suita to me. It looks like the regular Ozuku koppas that many folks sell and are good razor finishers in general. And that’s a nice looking stone BTW, congrats! Ozuku closed in the 1920s according to Alex Gilmore, and I’ve always suspected that these are actually hard Nakayamas from deep in the mountain at the end of the era. This one has some of the Nakayama ‘tells’, cloudy complexion, the thin diagonal line, and the ‘staircase’ layer on the side. But then Ozuku was close to Nakayama.

If you want a smoother edge, try thicker slurry. If you want a keener edge, try thinner slurry, and also try rinsing everything off after thin slurry finishing and adding 10-20 clear water strokes.
 
That doesn’t look like a suita to me. It looks like the regular Ozuku koppas that many folks sell and are good razor finishers in general. And that’s a nice looking stone BTW, congrats! Ozuku closed in the 1920s according to Alex Gilmore, and I’ve always suspected that these are actually hard Nakayamas from deep in the mountain at the end of the era. This one has some of the Nakayama ‘tells’, cloudy complexion, the thin diagonal line, and the ‘staircase’ layer on the side. But then Ozuku was close to Nakayama.

If you want a smoother edge, try thicker slurry. If you want a keener edge, try thinner slurry, and also try rinsing everything off after thin slurry finishing and adding 10-20 clear water strokes.
Thanks! I had a bit of a question about that because it was listed as suita on the link, but that term was dropped in the final description. Either way, it looks like they were correct when they told me that it would be a good finisher. Apparently, the katakuchi term indicates that the pores are tightened so I believe this means that it will be harder than a typical stone of this type, but I really don't know enough about JNats to know if this is the way this term is actually used.

Thanks for that tip, I'll keep experimenting, I have a lot to learn and I know it will take some time to get a feel for how the slurry should be worked and how it affects the final edge.
 

Steve56

Ask me about shaving naked!
Try diamond plate slurry too if you have a mellow one. If you don’t, use the tomo to break the diamond plate slurry.

Katakuchi just mean hard, or ‘hard mouth’ as Google translate makes it. The katakuchi kanji is just a square like you’d draw on paper in a second. I a.ways wondered about the ‘mouth’ part of the translation then it struck me, cartoons - the ‘hard’ kanji could make a cartoon mouth. ??

I have an image of a Matsunaga whetstone company stone that I got from Takeshi years ago that had the katakuchi kanji on it. If I can find it, I’ll update the thread.
 

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As Steve says is best. When going to Clearwater it adds keenness and takes some of the foggy finish from the bevel. The trick is to know how many laps of CW to go with as it makes a big difference fast. I shoot for a medium to thin slurry after a 10k stone. Then CW for just a few laps. No need to do hundreds of laps if you're going with synthetics up to 8k or 10k.

But, I'm far from a pro with Jnats.
 
Try diamond plate slurry too if you have a mellow one. If you don’t, use the tomo to break the diamond plate slurry.

Katakuchi just mean hard, or ‘hard mouth’ as Google translate makes it. The katakuchi kanji is just a square like you’d draw on paper in a second. I a.ways wondered about the ‘mouth’ part of the translation then it struck me, cartoons - the ‘hard’ kanji could make a cartoon mouth. ??

I have an image of a Matsunaga whetstone company stone that I got from Takeshi years ago that had the katakuchi kanji on it. If I can find it, I’ll update the thread.
By "mellow" do you mean a worn plate? I have a worn 1200 DMT so that might work, does the grit of the diamond plate make much of a difference?

I'd be interested in seeing that image if you should be able to find it.
 
As Steve says is best. When going to Clearwater it adds keenness and takes some of the foggy finish from the bevel. The trick is to know how many laps of CW to go with as it makes a big difference fast. I shoot for a medium to thin slurry after a 10k stone. Then CW for just a few laps. No need to do hundreds of laps if you're going with synthetics up to 8k or 10k.

But, I'm far from a pro with Jnats.
Thanks, I'm definitely going to experiment a bit. I was thinking that next I might try my usual technique of going to a 12K Shapton and then using the JNat as a finisher with CW only and seeing how the edge develops. I probably should have tried this first since it would give me an idea of how it performs in relation to other natural finishers that I use this way.
 
By "mellow" do you mean a worn plate? I have a worn 1200 DMT so that might work, does the grit of the diamond plate make much of a difference?
I can't speak for Steve56, but I bet he means a worn plate. 1200 sounds excellent.

I had had a set of diamond plates for 30 years, some sort of 3m diamond cloth with dots glued to an aluminum plate. Finally realized they were totally worn out when I spent like two hours trying to sharpen (flatten, really) a grinder disc, with little result. I came really close to throwing them out.

Those hideously worn plates are about perfect for making slurry.
 
I can't speak for Steve56, but I bet he means a worn plate. 1200 sounds excellent.

I had had a set of diamond plates for 30 years, some sort of 3m diamond cloth with dots glued to an aluminum plate. Finally realized they were totally worn out when I spent like two hours trying to sharpen (flatten, really) a grinder disc, with little result. I came really close to throwing them out.

Those hideously worn plates are about perfect for making slurry.
Certainly something I'll try as I experiment with the stone.
 

Steve56

Ask me about shaving naked!
By "mellow" do you mean a worn plate?
Yes

… does the grit of the diamond plate make much of a difference?

For Atomas I’d say no, BUT the amount of wear makes A LOT of difference.

The way that you know which of your plates in varying stages of wear to use, is to look at the finish it produces on your stone. Use the plate that produces the best/finest finish on your stones regardless of grit rating.

I have a mellow 600 Atoma that I use to finish the surface of my finest JNat finishers - and that’s all that I use it for. It leaves a much finer finish than my Atoma 1200 because the 1200 is ‘fresher’ and leaves fine scratches. Maybe not much of a practical difference, if any, especially after conditioning the surface with a tomo and putting a worn razor or two across it.~
 
Yes



For Atomas I’d say no, BUT the amount of wear makes A LOT of difference.

The way that you know which of your plates in varying stages of wear to use, is to look at the finish it produces on your stone. Use the plate that produces the best/finest finish on your stones regardless of grit rating.

I have a mellow 600 Atoma that I use to finish the surface of my finest JNat finishers - and that’s all that I use it for. It leaves a much finer finish than my Atoma 1200 because the 1200 is ‘fresher’ and leaves fine scratches. Maybe not much of a practical difference, if any, especially after conditioning the surface with a tomo and putting a worn razor or two across it.~
Would using tool steal work well to condition the surface? I have a 2" chisel I purchased to burnish my black Ark and have no other use for it lol.
 
Sure, should be great. Just don’t gouge the surface.
Yeah, I'll have to be careful, the black ark was impossible to gouge with the chisel, but I'm sure the JNat isn't so tough to chip. I imagine removing a large chip would be painful!
 
Yes



For Atomas I’d say no, BUT the amount of wear makes A LOT of difference.

The way that you know which of your plates in varying stages of wear to use, is to look at the finish it produces on your stone. Use the plate that produces the best/finest finish on your stones regardless of grit rating.

I have a mellow 600 Atoma that I use to finish the surface of my finest JNat finishers - and that’s all that I use it for. It leaves a much finer finish than my Atoma 1200 because the 1200 is ‘fresher’ and leaves fine scratches. Maybe not much of a practical difference, if any, especially after conditioning the surface with a tomo and putting a worn razor or two across it.~
With a low magnification for here is a new atoma 400
1-400.jpg

And now , Here under high magnification, the difference between a used atom 400 and a used Atom1200.
The wear and the grit of the atoms generates a big difference in the production of a fresh mud.
ATOMA 400.jpg



ATOMA 1200.jpg
 
With Jnats the size of the diamond plate grit does not matter that much, because Jnat slurry is friable and will break down with use. In theory a 400-grit plate will cut a 400-grit grove in a stone and produce grit about 400 grit wide and about 200 grit high, not 400 high because of the binder.

But in reality, the Jnat grit immediately breaks down much smaller quickly. Try it, you will not see 400 grit stria on your bevels. I regularly use 300-600 grit plates to flatten and make diamond slurry.

Larger diamond slurry can be more aggressive but, with use will become finer quickly. Added to the breakdown, is the swarf, micro bits of steel that float in the slurry and act as a cushion between the stone face and the steel. Which is another reason to thin your slurry and create new slurry for your finish laps to minimize edge impact damage and rebuild the edge.

To break in a diamond plate, sharpen a couple of kitchen knives and lap a couple stones, the goal is just to knock off any high diamonds and get a more even face.
 
With Jnats the size of the diamond plate grit does not matter that much, because Jnat slurry is friable and will break down with use. In theory a 400-grit plate will cut a 400-grit grove in a stone and produce grit about 400 grit wide and about 200 grit high, not 400 high because of the binder.

But in reality, the Jnat grit immediately breaks down much smaller quickly. Try it, you will not see 400 grit stria on your bevels. I regularly use 300-600 grit plates to flatten and make diamond slurry.

Larger diamond slurry can be more aggressive but, with use will become finer quickly. Added to the breakdown, is the swarf, micro bits of steel that float in the slurry and act as a cushion between the stone face and the steel. Which is another reason to thin your slurry and create new slurry for your finish laps to minimize edge impact damage and rebuild the edge.

To break in a diamond plate, sharpen a couple of kitchen knives and lap a couple stones, the goal is just to knock off any high diamonds and get a more even face.
Thanks, this makes a lot of sense.
 
With Jnats the size of the diamond plate grit does not matter that much, because Jnat slurry is friable and will break down with use. In theory a 400-grit plate will cut a 400-grit grove in a stone and produce grit about 400 grit wide and about 200 grit high, not 400 high because of the binder.

But in reality, the Jnat grit immediately breaks down much smaller quickly. Try it, you will not see 400 grit stria on your bevels. I regularly use 300-600 grit plates to flatten and make diamond slurry.

Larger diamond slurry can be more aggressive but, with use will become finer quickly. Added to the breakdown, is the swarf, micro bits of steel that float in the slurry and act as a cushion between the stone face and the steel. Which is another reason to thin your slurry and create new slurry for your finish laps to minimize edge impact damage and rebuild the edge.

To break in a diamond plate, sharpen a couple of kitchen knives and lap a couple stones, the goal is just to knock off any high diamonds and get a more even face.
I had specified “fineness of the mud particles before backdown process”

The first difference between Atoma 400 and Atoma 1200 can be seen in the creation of the mud. I agree with you on your remarks for the continuation with the break down of the mud.

As you specify yourself in the tread “Mohs Scale for testing the hardness of stones” “.A Jnat, like any natural stone can vary from one side of the stone, to the other, as can the Nagura.” Each Jnat, each Nagura will be different, they are natural stones, they contain what they contain.”

Some JNats decompose very quickly and others very slowly, if at all. We come back to the subject Hardness and friability described by Alex in the post ““Mohs Scale for testing the hardness of stones”

I find it funny to continue to exchange here on the same subject.

When it comes to the sharpening step 100% agree with you, in the end it doesn't make a difference thanks to mud degradation.

When it's the finish, the last step, and the edge is very thin and fragile, that's another story. The first hits with a fresh mud made with an atoma 400 and with a slowly degrading stone makes a lot of difference. Under high magnification this is perfectly visible.

OK I'm talking about something that brings an end benefit. Maybe @dabrock is not at this stage yet but if you want the next stage these little things are to be taken into account because as you say yourself "Honing razors is not just about sharpness"

But something tells me you want to add a final word. Which I would gladly leave to you.
 
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