My Jnat Journey
- Thread starter Tomo
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What?
It’s about the pressure?
Shazam!
It’s about the pressure?
Shazam!
Here are some great old photos taken by Seraphim many years ago that dramatically demonstrate the effects of pressure.
He took a photo of a piece of chalk, one with heavy pressure and one with light. Note the difference at the edge were the stria end.
It says all you need to know…Keep it simple.
He took a photo of a piece of chalk, one with heavy pressure and one with light. Note the difference at the edge were the stria end.
It says all you need to know…Keep it simple.
Steve56
Ask me about shaving naked!
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- #206
I like yours better!
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- #207
Cashew laquer is curing nicely. The Awasedo laquer has been down for two weeks. I think it’s about there. The Nagura lacquer has been down for a week. Feels dry but still smells a bit.
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- #208
Lapped and chamfered the lacquered Awasedo. I did the chamfers with sandpaper on glass to avoid gumming up my diamond plates with lacquer. The Ozuku on the left had some chippy edges from when it was cut. One edge is clean but the other one still has a few divots. I don’t think there’s and need to chase them out if I use the clean edge.
For me that's small enough to just lay a shallow chamfer that brings the edge in beyond the divot. Maybe hand sand the divot very lightly so it doesn't cause issues as you lap down.
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- #210
Did a test run on the Ozuku.
#2 Mikawa > Asagi JNS Nagura > Plain water
The feed back on the stone was very nice and I spent a while on each stage. The razor glided smoothly on the surface. This is a proven slurry progression for me and it worked beautifully on this stone. HHT was on point. First impressions of this stone are good. It seems to be an easy one. I stuck to the clean edge and didn’t feel the edge chips on the opposite side at all.
Does anyone know what you call this surface pattern? It looks a bit like a trout skin to me. The rough patch in the bottom right of the dry pic looks like little scales. You can you feel them at all but under magnification it looks like thin layers ready to flake off.
#2 Mikawa > Asagi JNS Nagura > Plain water
The feed back on the stone was very nice and I spent a while on each stage. The razor glided smoothly on the surface. This is a proven slurry progression for me and it worked beautifully on this stone. HHT was on point. First impressions of this stone are good. It seems to be an easy one. I stuck to the clean edge and didn’t feel the edge chips on the opposite side at all.
Does anyone know what you call this surface pattern? It looks a bit like a trout skin to me. The rough patch in the bottom right of the dry pic looks like little scales. You can you feel them at all but under magnification it looks like thin layers ready to flake off.
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Hard to be sure as pictures can be a bit deceiving but it looks to me like you have quite a bit of oxidation on the overall surface and some demineralization in spots but more heavily in the lower right. I would do some quick but heavy lapping. If the surface lightens in color it lets you know you have to go further to remove the outer oxidized layer.
There is a great video by KVJ on YT called Surgical Black Oozuku. (All time best honing video on YT IMHO) Pay attention to what he says in the beginning about oxidation and lapping.
FWIW, 3 of my 4 JNATs needed similar treatment. I think there are so many old stones being dredged up by the kids and grandkids of deceased elders that these are what makes up the majority of the stones being traded. Many of them were being actively used, suddenly stopped, and then just sat idle for decades. If they’re in use the surface stays fresh but sitting for 30 years, you have to knock off that top layer.
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- #212
That’s interesting. I lapped the stone but maybe I need to give it a little more.
Good video. I liked this one too. I wish that I found it earlier. He addresses some of the points that I’ve found to be important through my experimentation. Particularly around Aroma slurry and the importance of clearing slurry between stages.
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One thing that is a bit tricky is that, especially with a hard stone, lapping down to 140 or 400 on a stone finished to 600 and dressed with a nagura will in itself lighten the colour. If I lap a stone I haven't used for 6-8 weeks then the lapped layer will be lighter but I haven't been able to determine if that is because it oxidises really quickly or if I'm just changing the finish. I suspect the latter but I should test this point more systematically.
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You are correct. There are two factors darkening the color of a stone: oxidation and finish. A freshly lapped and roughed surface will appear lighter. Independently, removing the darkened oxidation will also lighten the surface. The important thing is to know your stone.
Attached are pictures of a Maruka Nakayama Asagi. It most likely sat for decades unused and the surface has extensive oxidation. The last picture is with most, probably 2/3rds of the oxidation lapped off. At this point it is easy to tell what was oxidative, and if you look close, what still is some thinner oxidation.
Note, the next to last picture which is the reflection on the surface before lapping. I’m not entirely sure if an oxidized surface is necessarily “bad” provided that it is very smooth like this and you are using a quality tomo nagura. The only way to be sure is to lap it. Plus oxidation is ugly and takes away from the natural beauty of the stone.
Edit: adding one more newer picture.
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- #215
Full Mikawa progression. It works!
The cashew has been down for a week and a half and it was time to play. I could not visually see any difference in the finish left by these stones. They all left a very fine and even looking finish. They did feel slightly different under the blade. I was surprised how much water they absorbed. The Tomo was a little too hard for this stone and gouged it up a bit. I switched to an Atoma slurry which seems to do the trick. Finished on plain water, 40 laps linen and 60ish on horse hide. Solid edge.
Gave the stone another good lapping after. I got the scratches out but I’m not sure that I’m through the oxidation layer. It is looking much cleaner though. There are parts of the surface that have what looks like flakes. The flakes are stable and can not be felt but they look a little unnerving. Similar to what you might see on an Idwal.
The cashew has been down for a week and a half and it was time to play. I could not visually see any difference in the finish left by these stones. They all left a very fine and even looking finish. They did feel slightly different under the blade. I was surprised how much water they absorbed. The Tomo was a little too hard for this stone and gouged it up a bit. I switched to an Atoma slurry which seems to do the trick. Finished on plain water, 40 laps linen and 60ish on horse hide. Solid edge.
Gave the stone another good lapping after. I got the scratches out but I’m not sure that I’m through the oxidation layer. It is looking much cleaner though. There are parts of the surface that have what looks like flakes. The flakes are stable and can not be felt but they look a little unnerving. Similar to what you might see on an Idwal.
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Steve56
Ask me about shaving naked!
Those are very likely bias cracks as @alx gilmore calls them. They’re fine cracks almost parallel to the surface and can be unstable/shed material. Not a bad idea to brush them with a fiberglass brush after each lapping. The fiberglass brush will remove any unstable material. You may be able to fell them after that, but only because some places will be low.
This is quite a collection. Not a koppa in site. Enough bricks to build a house. Watch at your own peril.
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- #219
I’m glad you find it interesting. I’ve had a lot of fun making it. As usual I’ve probably taken things a little too far. I hope that doesn’t put people off of JNats. I’ve actually come to the conclusion that JNats are far more approachable than I originally thought.
This was exactly what I got from the thread. It didn't put me off -- it made me think of them as more approachable. I have some stones on the way now (purchase decision heavily inspired by this thread), so we'll see how that revised option bears out in practice
