Gokumyo 20k consistency

I've had this hone for about 4 months and honed/touched up about 3 dozen razors with it.

Mine was not affixed to the base and so I have been using the "bottom" side to leave the stamp untouched.

I have found that the amount of swarf produced seems to vary from quite alot (for a 20k) to virtually none. The resulting keenness of the edge seems to vary as well.
I always lap with an Atoma 400, and it is definitely faster with a bit of slurry left behind, but I have not found this to improve the keenness.
I have tried using the 3k/8k rubber that came with it and this dramatically increases the swarf production, but I am nearly convinced that it is simply embedding coarse particles in the stone as the edge always seems to be set back when I have tried this.

Now, yesterday when I was lapping prior to touching up a couple of razors I noticed that there is a variation in the colour, a white band 5-7mm wide has formed on one edge and there is a hint of one forming on the other. The center region of the hone is very slightly yellow, and looking with a loupe I can see a mottled appearance. I need a better camera to show this, it is very subtle.

My thought is that I need to keep lapping and see if the center region continues to shrink. Judging by the chamfer on the edge, I have removed about 1mm since receiving the stone. The peculiar thing is that I feel like I had better results with the first few razors I honed.

Has anyone had similar experience?

You have to be absolutely sure the stone is flat. The Gokumyo 20k is a pretty hard stone that can take some time to lap fully. Second you want the surface very smooth, 400 grit scratches is way too coarse. I smooth mine with a coticule and the results are super consistent no matter maker, steel or grind. I do not get any swarf with mine as it should be expected from such high grit stone. I think as soon as you smooth the surface to be like mirror you will not see swarf anymore.

+1 on mainaman's post. I do three lappings on my 20k. Atoma 400, Atoma 1200 and finish the surface with a DMT 325.

Also because of the 20k hardness, each different razor may require a different number of strokes to refine the edge. You need to experiment.

I think I wasn't clear, my concern is that the surface is not uniform in appearance. The edges are pure white and the center is slightly off-white and mottled. I have the feeling that there is a layer or skin of bad material that has "settled to the bottom" during manufacture.
I guess my options are to keep lapping the backside or start using the top. Just wondering if anyone else has experienced this.

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I think that smoothing/polishing the stone surface will improve your chances of a better razor edge. Try a coticule like Stefan suggested.

Honestly, I would ditch that whole backside concept.
Take a picture of the stamps, then flatten it and use the intended side of the stone:)

And as the others has adviced, go to a finer stone for last polish of the stone's surface.

Talk to your vendor about the colouration issue. If it was/is someone like Stu, chances are they'll either know what it means or they'll follow it back to the manufacturer for you to get an answer.

Personally, I would expect a high-end synthetic to be reasonably uniform throughout but I don't know these stones. So your best bet is talk to the manufacturer I'd have thought.

James.

Mine is consistent in color but I don't use it very much.

I've had no issues with mine at all. Mine is white from end to end on both sides, and I do use both sides. I lap mine after every use using 400 grit wet/dry sandpaper and have experienced no issues with that either.
It has become my primary/only finisher and has displaced an Escher that I was using before. In my progression, it follows my 12K Naniwa SS and has caused my 16K and 30K Shaptons to just languish in their boxes.

I found I like the feel of the escher finish on my face/neck better than the feel of the 20k. I still need to use it more to really come to a conclusion, and I'll keep it regardless. If I'm going to sell a personal razor, or on the rare occasions when I hone someone elses razor, I'll trot it out and give them the 'scary sharp' edge.

I lapped the top side and it is uniformly white. The off-white layer on the bottom didn't appear until I had used the hone for a month or more. I recall that I thought it was just a patch of swarf that needed to be lapped away, but instead of shrinking it grew larger. I think this also explains why I had such good results early on and rather inconsistent results more recently.

Mine also has dark yellow streaks on the bottom where it rests on the rubber base.
I wouldn't mind betting it's staining from the rubber.

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Originally Posted by onimaru55

Mine also has dark yellow streaks on the bottom where it rests on the rubber base.
I wouldn't mind betting it's staining from the rubber.

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I was thinking of that possibility myself, though as of yet I only had a bit of black staining as zib described on his. No yellow yet , but as I noted before, I haven't been using it much.

Would also explain the very geometric shape of the discolouration, perhaps?

James.

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Originally Posted by onimaru55

Mine also has dark yellow streaks on the bottom where it rests on the rubber base.
I wouldn't mind betting it's staining from the rubber.

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The bottom of mine has never been in contact with the base. It came packaged separately and I have always set it bottom side facing up.

Whatever the stain is, it was either not improving or even reducing the HHT from a Shapton 8k. I just touched up a TI on the 8k and then the newly lapped top of the 20k and there was a clear improvement in the HHT. I will shave with it in the morning...

I HAD been suspecting the 8k to 20k was to big a jump and now have a 16k GS in the mail from Stuart.

Mine came on the rubber base and was stuck to it. I don't remember any yellowing, but I did lap the bottom to get rid of the sticky surface. I also decided to use the bottom to hone and to preserve the upper stamped side. I've never used the rubber base after unpacking it. Now the stamp side which is down and was white has yellowed along the length of the stone. The upper lapped side is a clean white.

It does sit on a steelex stone holder which has 3 rubber pads that are a similar rubber, but the yellowing isn't just at the contact points of the pads which are stationary, but its all across the now lower stamped side of the stone and also on the sides. :shrug:

Edit: Based on gadaiver, post #18, mine is a second generation too.

The label side was slightly yellow before lapping but the pure white surface was exposed very quickly.

What I am seeing on the bottom is not yellow, but more of a mottled off-white texture. I should add that I have removed about half a millimeter of the bottom between yesterday and this morning, so this is not a surface stain.

This is what I received from Stuart regarding the different generations of stones:

The newest stones are third generation. First were fixed to their rubber bases and the original type, the second was introduced for uniformity with the rest of the line-up and featured a stone not solidly fixed to it's base. The third generation are the same, but the stone itself is wrapped in plastic by Suehiro due to some problems we discovered with the stone/base being in contact with each other between manufacture and delivery in the second generation. It seems that the stone in contact with the rubber base absorbs something from the rubber, and can cause some inconsistent performance in the side of the stone that was in contact with the base. So long as you use the 'up' side exclusively, you shouldn't have any problems of any kind.

I've got a second gen stone. I've never used the logo side and that side did absorb a bit of black/gray staining from the base. Works well so far on any razor I've used it on. Of course at that grit level I only take a truly shave ready razor to it for final enhancement. Trying to get to shave ready with such a stone, whoever makes it, is not the correct approach IMHO.

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Originally Posted by JimmyHAD

I was thinking of that possibility myself, though as of yet I only had a bit of black staining as zib described on his. No yellow yet , but as I noted before, I haven't been using it much.

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The only staining I ever noticed on any stone was some black and yellow stains in the 4k side of my Norton 4k/8k combo. No staining on either side of the Gokumyo 20k.

I used marker on bevels just to see how quickly Gokumyo would polish. It stained "quite easily". Had to remove those stains with other stone. I guess they have a tendency to stain...

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Originally Posted by offshoot

I used marker on bevels just to see how quickly Gokumyo would polish. It stained "quite easily". Had to remove those stains with other stone. I guess they have a tendency to stain...

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Yes, that is my impression after a 1000+ razors on it.
Even tape will leave stains on it sometimes.
Rather than lapping it though, I just scrub it with a brush after every few razors, and that has kept it going for more than 18 months without lapping:)

Same here.

Mine is a 3rd gen stone, lapped up to 1000 with an atoma it collects a patina from taped razors, even steel, quite quickly.

If the surface is smoothed over with a translucent arkie after the atoma and the residue washed off, it will still stain with metal, but not as quickly. The arkie soon removes the patina, but I have to wash it off as it will smear into stripes if anything is left on the surface.

Regards,
Neil

The 1k/4k(i may be mistaken on the grit) works very well to remove swarf. My stone has about 200 razors on it and it feels harder than when I first got it. First hone on it felt like a naniwa 12. Im considering shelving it as my Jnats are producing much smoother IMO. I havent shaved off of it in 2 months, honed one for myself on it and it felt harsher than I ever remembered it to be. A great shave, but the smooth off the natural is hard to beat.