Japanese Natural Stone--Best Practices

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Mucho Bocho

Mucho Bocho

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I just picked up my first Japanese Natural Stone from Maxim. Its a Aiiwantani http://www.japanesenaturalstones.com/sold-jns/

I've watched Jon's and Maximx videos on the subject. Read a lot about sword polishing too. I put three coats of Cashew lacquer on both the stone and nagura and mounted the stone to a thick hardwood base. I realize that there is just a lot of trial and error with gnats. Just hoping some of you will share your trials and tribulations to make my journey a little less painful. I'm sure i'm not the only one with these questions.

Now my questions:

1.) After using the stone, do I wipe it off and let it dry or just leave swarf/mud on it and let it dry by itself?

2.) Should I put some polyurethane on the wood? The glue I used is waterproof and the bottom of the stone is heavily lacquered, but when spraying the stone, I notice that the top of the wood stay a little damp.

3.) So far, i've only been able to create sharp edges, but their a little too slippery for my taste (blue, white, good stainless). I'm not overworking the bevel at all either. Using just a few strokes on each side and light touch. These knives are not that dull to begin with either. Do j-nats require more "working" time? My takenoko only takes one strop to two to get grabby, sticky edges.

4.) Can gnats be used as a dry strop?

5.) Doug just sent me some beautiful Uchigomori finger stones from Oohira, can I use those? I think I have some finger stone monzento too, can I use that to create the slurry?

6.) Whats the deal with Nagura's? I thought they were all small till Maxim sent me one larger than my stone. Can nagura's be used to sharpen on? What the hell is a nagura? What are the different types and how are they used?

Really appreciate some insight here.

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Hi Mucho! I tend to leave the swarf on the stones to dry. The only concern is to leave it in a place so it dries slowly in order to prevent cracks (same with synths). As for your edges not being so toothy, i think the best should be to try a coarser jnat to finish or to pre-finish it (for instance, Ikarashi or Aizu). Whenever Maxim has his Numata back on stock, you could try it also. Another stone that is finer than Numata, but (at least mine) leaves a toothy finish is the Takashima from JNS (the Takashima from AFrames is much harder and finer, from what i've seen so far). The Takenoko is a wonderful synth, isn't it? My favorite synth on the 6k-8k range. As for your other questions, i'll leave it for the more experienced to answer. Hope this helps!
 
Holy crap. I think your Aiiwatani is your nagura. Ha! Defiantly try honing on the larger stone. A nagura is a stone (usually smaller) used to raise a slurry or clean the base stone. Take a look at the site Tomo Nagura. It's a razor hone site but has a lot of good info on jnats.
 
Can't tell from the pictures how much slurry you generated with the Tomo nagura, but I'd say be pretty generous with it especially if you are sharpening narrow beveled knives. I haven't enjoyed the feeling of sharpening on nats without a good slurry buffer. And if you're using this after fine synths then it may take more than a few strokes to refine the synth scratch pattern
I too have a larger Aiiwatani tomo nagura from Maksim, it creates a nice fine slurry and itself isn't of the shape and cut to use as the sharpening stone, so I guess that can be why it fits the bill of nagura?

Edit: got a better look at the pictures, I assume the tomo nagura shot shows it covered in mud but dried out? In that case looks like you were generous enough on the slurry
 
Mucho Bocho said:
I just picked up my first Japanese Natural Stone from Maxim. Its a Aiiwantani http://www.japanesenaturalstones.com/sold-jns/
**
I've watched Jon's and Maximx videos on the subject. Read a lot about sword polishing too. I put three coats of Cashew lacquer on both the stone and nagura and mounted the stone to a thick hardwood base. I realize that there is just a lot of trial and error with gnats. Just hoping some of you will share your trials and tribulations to make my journey a little less painful. I'm sure i'm not the only one with these questions.

Now my questions:

1.) After using the stone, do I wipe it off and let it dry or just leave swarf/mud on it and let it dry by itself?

* I leave swarth on my stones like Marcelo, haven't had any problems.

2.) Should I put some polyurethane on the wood? The glue I used is waterproof and the bottom of the stone is heavily lacquered, but when spraying the stone, I notice that the top of the wood stay a little damp.

*Why not? Couldn't hurt

3.) So far, i've only been able to create sharp edges, but their a little too slippery for my taste (blue, white, good stainless). I'm not overworking the bevel at all either. Using just a few strokes on each side and light touch. These knives are not that dull to begin with either. Do j-nats require more "working" time? My takenoko only takes one strop to two to get grabby, sticky edges.

*Many Jnats are very fine and will polish the edge when the slurry breaks down. Good for Yanagiba and some other single bevels but often too fine for Gyuto. That said , every natural stone is different and will produce different results with various steels and edge geometries. As Marcelo points out mid grit jnats will give you a toothier edge. I like to start with an aoto or aizu then finish on a finer jnat. Sort of like the 1000, 6000 synthetic progression. Keep in mind that some naturals will be better suited for edge sharpening and others will be better for Kasumi polishing.

4.) Can gnats be used as a dry strop?

*Never tried it. ??

5.) Doug just sent me some beautiful Uchigomori finger stones from Oohira, can I use those? I think I have some finger stone monzento too, can I use that to create the slurry?

* Might as well give it a try. Badgertooth , XooMG and others are rubbing full size aoto and other jnats on a Thai bensui with good results. You'll be thinning the Uchi as a bonus. It is fun to see what happens when you mix stones and their slurries. Usually the softer stone will contribute the largest percent to the slurry. Uchigumori can be coarser then think sometimes.

6.) Whats the deal with Nagura's? I thought they were all small till Maxim sent me one larger than my stone. Can nagura's be used to sharpen on? What the hell is a nagura? What are the different types and how are they used?

*As I mentioned the site Tomo Nagura is a great source of information on jnats and nagura. Tomo nagura means the nagura is the same as the base stone as in your case I believe they are both Aiiwatani. To make things a little confusing some large bench stone from certain mines are called nagura. These you see in Katana polishing.

Really appreciate some insight here.

*Hope this helps you have fun with your new stone.

Doug

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**
 
Doug, Thanks for the input. I thought we had more members on the forum that use Japanese natural stones.

Unfortunately patience isn't one of my strengths, and I'm used to my synthetics working instantly, so this stone and me haven't jelled yet.

I polished up my Toyoma petty and needed to do the same to the edge. This time I used less water on the stone/nagura. It finished up with a nice sharp edge, somethat sticky, but still did not have that instant bite, fingers do not slide at all.

I messed around with different sharpening angles but did not really overwork the edge. In the end, I was able to get the knife shaving sharp, dropping through tomatoes and shredding news print, but the edge is still a little too slick for my taste. I'm going to keep at it, I'll discover a solution sooner or later. I've heard good things about this stone and so I think its my technique that needs more work.

Still like to get some more input from the jNat Vets, you know who you are.
 
I had the same 'problem' with a nakayama. My solution in the end was to start with one or two drops of water which allowed the blade to grab the stone rather than skate along it, as swarf and mud formed I was able to add a few more drops of water. That produced a sticky edge. The wetter sequence which didn't ever grab and swarf up was more like a super fine honing that left too slick an edge for my liking.
 
Most natural stones have irregular and more or less firmly held grit, unlike synthetic stones with very sharp edged and less tightly held grit. That means the grit is usually fairly blunt on natural stones and sharp corners fracture off or the grit crushes and becomes more blunt. A slurry gives you sharper grit because the particles wedge into the firmly held ones and stick up above the surface, increasing the local pressure and exposing sharper corners.

Every natural stone has it's own "personality" and you will have to experiment to see what works best for you. Typically, however, Japanese stones require slurry to cut quickly, and when used with only water tend to polish or burnish the edge rather than grind steel off. If you start with slurry, raised either with another stone or a fine diamond plate and finish with only water you can get both sharpening and polishing on the same stone.

If you want to get tricky, get a selection of nagura stones ranging from fairly coarse to fine grit, and work up a slurry from each in succession on your hard finisher -- that way, the stone isn't doing anything but holding the grit from the nagura in the slurry. Each nagura will give you a different effective grit size, and you can finish with the bare stone and water. This is a typical razor progression on natural stones, so it may not work well with knives, but illustrates the theory anyway.

Note that burnished edges tend to hold up better than edges ground with finer but sharper abrasives. this is true of woodworking tools too, which is why I've been finishing plane blades on natural stones recently. Works pretty well, although it's not fast.

Peter
 
So i've spent a little more time with the Aiiwantani natural stones and its nagura. I just used a drop or two to get the slurry alive again and am able to get sharper, grippier edges. But I'm still giving them a final strop on the Takenoko for that extra bite. I now understand what others mean about the feel of quality carbon steel (Shig, Kato, Carter) on a nice Japanese Natural Stone. Erudition for sure.

I haven't gotten into mixing different naguras, slurry stones or Uchimgori... Just trying to test one variable at a time.
 
I don't think it matters if you wait for the stone to dry before you put it in storage. Just keep it from heat if you want to avoid cracks
 
Vysis said:
I don't think it matters if you wait for the stone to dry before you put it in storage. Just keep it from heat if you want to avoid cracks
Click to expand...

This doesn't address op's question... Finer natural stones dry pretty quickly as they can largely be used splash and go, the query was with regards to slurry management since the slurry is an integral part to using these naturals
 
So I have a related slurry issue...
My best results on an edge come with single or wide bevels, where the initial polishing of the bevel/blade road creates masses of lovely slurry, which gets ground finer the longer I polish, and thus when I come to the edge I am able to get it screaming sharp, using all this slurry. (This is all wonderfully enjoyable I might add!) When sharpening my other double bevel edges (non wide bevel gyuto for example) however, there is no prior work to create and refine a good slurry, so it takes a very long time indeed to get to anything approaching the same state. Depending on the stone, I do use a nagura, but even then I just raise a light slurry, and usually have to return to the nagura half way through to create more. I have not managed as of yet to get as good a slurry or as good an edge on any of my double bevel edges.

So a few queries I suppose-
Am I creating enough slurry with the nagura, should I be working it longer until a relative mudfest like with single bevels?
Do most of you keep the mud created in the heavier sessions? And if so how, just in a ziplock baggie?
I feel that in the initial edge work on gyutos etc, where the slurry is minimal, I'm not really doing much to the edge, and end up with this slippery edge with no bite, much like how mucho described above - is this work actually detrimental to the edge, fatiguing it by excessive polishing, until the slurry state is achieved where real sharpening is possible?

It seems a lot of our tentative first steps with nats come across very related issues, and I hope that any answers will be helpful with your own problems! Suffice to say it's a very enjoyable learning curve.
 
I have never used a jnat but couldn't you just let the slurry dry on the jnat so it would be ready to use the next time?

Jeff
 
Jacob, Good content! I've been leaving the slurry on the stone. I will refresh it each time I sharpen using the Nagura Maxim supplied when I bought the stone. I found this info on Nagura that I found insightful:


Quote:
What are the 12 layers of Nagura. Which mountain(s) or mines do they come from in Aichi prefecture? What are the differences in density and fineness of grit and other charactoristics of the stones in the 12 layers?


From the top

Mejiro
Tenjyo x2 layers
Serizuna
Buchikou
Koma
Botan
Yae-Botan
Mushi
Atsu
Ban
Shiki-Ban

I don't think anyone out of Japan knows this....

Only a couple suit tool sharpening. Koma, Mejiro, Tenjyo, Botan are the most popular.
 
In order to get more slurry, you could use a nagura of the same stone (i do it all the time with a Tsushima nagura on a Tsushima stone) or, if you don't have such a nagura, to create some by atomizing the stone.

In terms of creating a toothier edge, what works best for me is use jnats from start to finish. For instance: omura > JNS Numata (coarser and faster than the other Numata i've tried) > Ikarashi (coarser) / Aizu (less coarse) / Takashima (finer) / Hakka (finest). Also test for the toothiness as you use the stones. Once you reach the level desired, stop. Another thing is i feel there are some blades that are simply toothier than others, Kato nakiri being the toothier i've seen so far.

Another stone that leaves a bitting edge is aoto, if you manage to get the right one. Aoto seems to vary a lot. From the three i tested, one is ridiculously thirsty and coarse, actually leaving a nice and lasting edge, although it's terribly slow (i like to use those on the easiest to sharpen crappy stainless steels); the other is fast, thirsty but not as thirsty as the first one, making a lot of slurry in no time, leaving a bitting edge; the third is much harder and finer and not thirsty at all, still reasonably fast, and good to be used as a finisher for harder steels or pre-finisher before the ohira suita.
 
Don't possess an aoto as of yet. On the list however!
What do you mean by atomising the stone Marcelo? I only have a couple of nagura sent with a stone from Shinichi, one a nakayama and one a shoubu.
I always leave the slurry on the stone when finished, but I find it never picks up where I left it the next time I come to it! Think I will start saving the slurry from big wide bevel sessions. And bulking out the nagura selection!
 
Hi Jacob! Yes, the dried slurry when watered never seems to be as dense as before it dried! By atomizing, i mean to use your Atoma plate or similar on the stone to raise some slurry. I once opened a thread asking more experienced sharpeners what they thought about this method as opposing to using a nagura. It looks like the nagura is the safest bet, specially for razors due to their more fragile edges. However, for knives, i came to the conslusion that it should be an ok method if you need to create extra slurry. Maybe best to use a nagura, but it's not easy to find the right one for each stone we have.

http://www.kitchenknifeforums.com/s...d-plates-Vs-Naguras-on-Jnats?highlight=nagura
 
Yeah when I got my first nat I used my dmt on it, but for some reason have been dissuaded from it - think I've read it's better practice to not use diamond plates on your nats. But especially when unsure of which nagura to use it seems an attractive prospect, as you get a pure slurry of whichever stone you are using, rather than a compound of the stone and a possibly different nagura. Maybe I will play around with it again. Thanks for the link!

It has occurred to me it was mentioned by Krassi, in a similar recent post, who mentioned not using diamond plates on nats after posting a video of him using one years before, I will ask him why he thinks better not to.
 
If you think about the diamond plates which are diamonds impregnated on a flat metal surface, they tend to be much more exposed than a stone where the abrasive and binding/rest of the composition of the stone sit much more on the same plane. The diamonds which instead stick out will gouge deeper into the stone vs a nagura. You're getting less fine slurry to start with though because of that coarser/deeper cutting action are kicking up slurry fairly quickly.
But also, if you've read Maksim's natural stone wiki posts, particularly the one on how to flatten then lap against several stones in progression to get the smoothest finest surface so you can access the true fineness of the stone (particularly relevant for finer stones), using diamond plates for slurry generation are going to undo some of that work.
Whether or not that differential matters for kitchen knife usage is another matter
 
Im quite new to jnats and still dont fully understand the slurry thing. Some stones should only be used with slurry created by nagura (or less desirably diamond plate)? Or first without slurry then with slurry? I heard Suitas can/should be used without slurry?
 
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