Suehiro Gokumyo 20k updated opinion.

My Gok 20k arrived just on 2 years ago, and at the time it was the 'panacea' for all honing issues. It was. And it still is the number one choice for people honing straight razors on synthetic hones as the final stone.
I have made however a few observations. There are 3 'Gokumyo' series stones from Suehiro, I have owned, a 1 micron 10k, a .75 micron 15k and the .5 micron of the 20000 grit stone. I have since parted company with the 10k and the 15k, as either or both could admirably fill the role of 'finisher' in their own right. I recall the comment that there is swarf on the 20k after only 10 or so strokes. This is where the true position of the 20k is mis-read.
Thinking that metal particles after 12 strokes on a 20k .5 micron stone is ridiculous. That dark streaking that can appear on the surface of the 20k, is not swarf, it is a part of carbon steel, 'Graphite'. It is very much like the lead in a pencil. As a test, take your Gok 20 and run the spine of a razor down the hone. Now you understand. Equally do a dozen stokes on a taped razor. Now do it un-taped, the dark on the stone is multiplied. As a result of this, I use the cleaning stone maybe 3 times just honing one razor, finishing. A couple of strokes with the cleaner stone, wipe it, and you have a slightly dis-rupted surface, and the end result is superb. So, to say that after a dozen strokes on your 20k, that there is suspended steel in the liquid simply is not the case. Still a great stone, just a tip, remove that black stria blocking the pores of the hone with the cleaning stone, you will get much better results on the 20k when it's cleaned of the graphite.

I like to spray mine after about 10x & maybe a finger rub, followed by another spray. Normally, doesn't take much more than 10x anyways to get a fabulous finish. It's one of my favorite finishers.

With all due respect, the hone doesn't just "pull graphite" out of the steel... It certainly is cutting the steel and embedding it in the hone. This is a fast cutting stone for a 20k likely because it has a fairly high ratio of abrasive to binder.

Agree Scott, I would just add, that IMHO you can go straight from an 8k to to the Gok 20 with little problem at all, hence, my like of having a clean surface as well as a slight disruption of the surface, which I like on most of my synthetics, clean stone free of anything blocking the pores of the stone. I might end up doing three sets of 5 laps, with a slight clean in between, especially on a razor I am experimenting with. I have gone from 4K to the Suehiro, simply to see what it behaved like. All I'd say, is I finish up with a dozen laps on a progression of Naniwa superstones , the 10k, and as you rightly say 10 or so laps on the 20k and the strop is the next step. They were a remarkable stone 2 years ago, and I haven't seen anything better since.

My only point re 'Swarf'. Was that there is no steel particles in the solution on the hone, You can of course see the darker patches, but unlike stones that have swarf, it is obvious that there is steel 'in solution'. Take your 20k with the darkened areas and rinse it under a tap. The dark patches will still be there, as you put it, 'having not been pulled out of the stone' Clearly there is a movement of particles from the razor to the hone. But is it steel particles in solution (Swarf)? caused by the abrasive stone. On my other stones, if swarf builds up, I just rinse it off, gone. Same as if you write on the hone with pencil, once again it won't rinse off, you need to use a lapping plate to remove it. Is that swarf? to me, 'swarf' is metal particles from the razor you are sharpening, being separated by the abrasive, you don't need a lapping plate to get rid of swarf, just a rinse off. Just an opinion, I respect your view.

Yes, it's swarf, it's just embedded in the stone. Swarf by definition is just metal particles removed by a cutting or abrasive tool. The SG20k is not a friable hone - as I'm sure anyone who has used one will agree. The particles removed are very small, and get mostly locked into the surface of the stone. Some can be rinsed away with a little finger scrubbing still though. Those hones that don't embed particles much are usually friable stones, so that some particles of the stone come loose as they are dulled or packed up with swarf.

Interesting read. I have been cleaning the swarf from my 20k with a coticule. I have been too lazy to test it,but has anyone explored the merit of using the 400 grit cleaning stone vs finer stones,IE a rougher vs smoother finish on the 20k? It stands to reason the supplied rubbing stone may provide a more aggressive honing experience than using a coti to clean the stone as I have been doing.

Yes, I too have had better result from regular cleaning, I have use the supplied dual grit stone, small arks, coticules, high grit diamond plate and scotch brite sponge.

Most anything improves the finish on the razor. If I am at the bench I use a small stone or scotch brite, if at the sink a 1k diamond plate.

I find keeping the stone clean does make for a more uniform stria pattern or polish. I clean frequently or when I feel the stone is not cutting.

I also do the same, with the Naniwia 12k. When I don’t, I find irregular stria on the bevel.

I'm not convinced a stone can selectively remove carbon from steel.

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Originally Posted by Euclid440

Yes, I too have had better result from regular cleaning, I have use the supplied dual grit stone, small arks, coticules, high grit diamond plate and scotch brite sponge.

Most anything improves the finish on the razor. If I am at the bench I use a small stone or scotch brite, if at the sink a 1k diamond plate.

I find keeping the stone clean does make for a more uniform stria pattern or polish. I clean frequently or when I feel the stone is not cutting.

I also do the same, with the Naniwia 12k. When I don’t, I find irregular stria on the bevel.

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Fortunately for me, I guess, I don't hone that much, so I haven't used the 20k a lot. I'm sure you've seen this post of bobski's contact with Stuart of Tools Of Japan. Of course cleaning with a diamond plate is not as rigorous as lapping, but I'm spooked about going near my 20k with a plate now. For cleaning swarf, IIRC, I probably just hit it with a nylon bristled fingernail brush.

Yea, under running water and very lite pressure, maybe 3-4 laps. Even using stones or scotch brite, flood with water, a few scrubs, it good to go.

The Naniwa take a bit more laps, and for it I use a 300 or 400 plate.

I little dish soap as you use the DMT a few laps , eases the cut of the plate & attaches to micro (like that word :D) swarf. This cleans the hone faster , as the water flushes the soapy swarf away.

Jimmy, Stuart Tierney gave the Atoma 400 the green light, only the 1200 was advised against. And EKretz, I have had a play with some pencils, lapping plates, and thought about the results I found. I do believe Sir, you are correct, and I withdraw the swarf issue. The bell rang for me as far as your saying the metal had embedded in the stone. I went and looked at three different grit stones, with some soft lead pencils. I couldn't rub them off with a hand or cloth, but I had to rub for a while with an Atoma 400 to get a full grid of pencil off, indicating, you are indeed correct, based on the fact that to remove the pencil marks on a gridded stone, you have to take small amount of the stone, to get out what is in the surface of the stone. An excellent thread,
Cheers Bob.

Personally, I like using a JNat tomo to clean/condition my SG20k. It does a very nice job of cleaning out the swarf and also leaves a nicely wettable surface that doesn't cause water to form beads and leave large dry areas.

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Originally Posted by bobski

Jimmy, Stuart Tierney gave the Atoma 400 the green light, only the 1200 was advised against. And EKretz, I have had a play with some pencils, lapping plates, and thought about the results I found. I do believe Sir, you are correct, and I withdraw the swarf issue. The bell rang for me as far as your saying the metal had embedded in the stone.I went and looked at three different grit stones, with some soft lead pencils. I couldn't rub them off with a hand or cloth, but I had to rub for a while with an Atoma 400 to get a full grid of pencil off, indicating, you are indeed correct, based on the fact that to remove the pencil marks on a gridded stone, you have to take small amount of the stone, to get out what is in the surface of the stone. An excellent thread,
Cheers Bob.

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The head of Shapton USA, Harrelson Stanley, used to say that you could tell the stone was flat when the color was consistent from end to end .......... IIRC.

Somewhere along the way someone posted about the pencil grid. I always wondered if the pencil lines went a bit deeper into the surface necessitating removal of more stone. I figured it did, but figured it ain't much.

I've laid a pencil grid down and honed on it, to see how quickly it would wear off, and where the most wear would occur. Kind of an interesting experiment, that I'm sure others have tried.