Show your work! Uchigumori and co...

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EricEricEric said:
Lots of great information 🙌🏻

I didn’t consider pressure at all 🤔

For my nakayama tomae and shiro nagura pressure doesn’t appear to be the essence of the result, however on other stones it did seems that accidental burnishing streaks could appear if too much pressure was applied, further more with yet other stones max pressure never resulted in burnishing.🤷🏻‍♂️
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This is exactly why it so hard to make generalizations. A lot of it can come down to the stone in question. Nakayama tomae, like the one you have, can be utterly sublime ultra-fine stones. Not nearly as glassy or fussy as some others can be. You can polish with a lot of pressure or very little pressure and both can work well. Trying that approach with a murderously hard kiita or iromono or asagi would very quickly frustrate you. I find most people - myself very much included - get burnishing unintentionally in areas with greater convexity, such as the tip, as the surface area in contact with the stone decreases.

So hard to make generalizations about polishing.
 
Interesting topic about polishing/burnishing !
At first, we could think it is a difference of abrasion, but I am slowly understanding that it is not that simple and depending of the type of stone you can be very surprised : a mid grit mid hard stone, freshly lapped, will abrase like hell and will surely make a kasumi easily with a normal amount of pressure. But as the surface of the stone get polished by the knife and abrasion, the stone start to glazed and will not abrase as it was and will finally only burnish : the iron was very dark will become very light color and details will appear. I really advise people who want to try jnats for their ability to show details to try a mid hard/hard mid grit stone because you can really play with the stone and get both kasumi and burnished surface really easily. Most important, those mid grits don't scratch when you start burnishing, meaning start to rub a knife on a hard closed surface with only water. What finer harder stone will most often do (but there is exception).
For the awasedo, it is different : Most hard stone (razor stones and most tool stones), will be so hard and maybe because of the abrasive size, will pull on the iron if you try to burnish with pressure and without slurry, meaning you will get a huge scratch like a comet on your bevel and stone. That's why, most users keep the slurry on those stones and use light pressure : you keep the abrasion and you don't directly rub the knife on a hard surface.
But there is exception ! and that's when you realise you know about nothing and you realise nature can make some crazy things : I got a stone that will only burnish, which is very hard, and will not pull iron at all. Like magic. Why it does, I don't know ! but there is something in the texture, the composition of the stone, even that it is so hard, that will avoid that pulling effect.
@KenjiF I am not sure about what you say : if I burnish a surface with synthetic, then my jnat will struggle to abrase. If you go directly to a very hard stone, maybe, because you will put a burnished surface on the hard (maybe burnished if you did not lapped) surface of the stone. But most of the time, after a synthetic progression, even if you get a perfectly burnished surface at the end, you will grab a soft or mid soft jnat to make the bridge and burnished or not, the stone will abrase the knife and will quickly make a kasumi.
 
milangravier said:
I really advise people who want to try jnats for their ability to show details to try a mid hard/hard mid grit stone because you can really play with the stone and get both kasumi and burnished surface really easily.
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Like an Aizu/Tajima?
In all another nice writing, thanks for the input as always!
 
dragjp said:
Like an Aizu/Tajima?
In all another nice writing, thanks for the input as always!
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Yeah, Aizu, Tajima, Ikarashi, Mikawa naguras... The one I am thinking is my Kasabori, a kind of fine and hard Ikarashi. There is so many mid grits and if you accept the compromise to be in the 3k/4k grits range, you can get some amazing finish that only best fine awasedo could do.
 
Yes, the finish depends on both the stone and steel, and the only way to find good stones is to try multiples. That‘s why sword polishers have several different uchigumori, and why I have several different uchigumori for knife polishing too. The same stone won’t make the same finish on different blades, even from the same manufacturer. I have a Takeda sassanoa that’s a bit more finicky than the other Takedas.

Here’s an uchigumori fingerstone finish on a Masahiro Virgin Carbon. Apologies for the imperfections and poor image quality. This knife does get used, so I spiffed it up a little for the photos.

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Here are some uchigumori pieces that I’ve accumulated over the years. The stuff in the plastic bags came from Yahoo Japan, the person listing said that his father was a sword polisher that had retired and he was selling off the stones. They looked very pure, and they are, and several are shaped. The larger chunks came from several sources, Yahoo, Takeshi, etc. The white one is mostly gray on the back, but maybe closer to the shiro layer. Narutaki stone lower right.

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For knives, at least when you don’t demand a traditional process like when finishing a historical sword, many stones make an indistinguishable finish. As mentioned before, a soft tomae, but also akepin, hachmai, Hakka, soft kiita and iro, all these can work really well, depending on the particular stone.

When I did the Masahiro above, I was just learning what worked and what didn’t. If I were doing it over, I’d stick with high quality sandpaper on a flat surface up to about 2k grit, then switch over to JNats for finishing, testing a few to see which ones worked best on the particular blade.
 
Life has been pretty crazy lately but I’m trying to get back in the swing of things as far as polishing is concerned. Don’t be surprised to see me snatching up some stones in BST in the next few months!!

In the meantime to hold me over I was lucky enough to grab a @Illyria Kiridashi through @ethompson the other day and had myself a good lil time last night. Great little marking knife that is absolutely perfect for testing stones. Fantastic banding and a lot of character make this one of my favorite purchases. I went full natural progression and stopped with a Narutaki Suita.
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This is a Dua Vua cleaver I kind of went to town with.
It’s never going to be a pretty knife, so I call it a “Dirty Cleaver”
I think it’s ready for a new handle.
 

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ethompson said:
Okudo suita! And at least 8 others before you see littered in the background haha
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do you do any edges off that stone?

I feel like I'm in a tiny minority of folks using Okudo suitas for edges around here but I dont know if it's because folks don't like them or if it's just because theyre such hard stones to get a good example of.
 
ethompson said:
Okudo suita! And at least 8 others before you see littered in the background haha
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That’s a nice looking suita!

Idid a little polishing too, testing a piece of uchigumori that I don’t remember a lot about. The test victim was the usual Masahiro. I only polished the lower part near the edge, and you can see the transition. Th brown spots in uchi are always of concern, but I try to stay off them as much as I can, and no scratches this time.

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tcmx3 said:
do you do any edges off that stone?

I feel like I'm in a tiny minority of folks using Okudo suitas for edges around here but I dont know if it's because folks don't like them or if it's just because theyre such hard stones to get a good example of.
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I like them a lot for edges. The edges from them seem to have a bit of a ‘bite’ for the things with ‘skin’.
 
tcmx3 said:
do you do any edges off that stone?

I feel like I'm in a tiny minority of folks using Okudo suitas for edges around here but I dont know if it's because folks don't like them or if it's just because theyre such hard stones to get a good example of.
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It’s fantastic! Helps that size lets you do large gyuto like this 250 easily in one sweep.

Okudo in general are hard to find and then many of them are brutally hard and less suited for knives as opposed to tools. So great knife examples just aren’t as common as a lot of other stones people tend to speak of more for edges. But they’re some of my favorites if you get a good one.
 
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