Thread: 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.

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.

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.