Thread: Tsushima "Ocean Blue" 12K

The best I can tell from my stone, it is not a Tsushima mountain and it is not an ocean black. It is very hard and very smooth. Although the razor finish looks like a mirror finish to the naked eye, if it is examined at 30 - 60x, there is some haziness, just as other have reported with a JNAT.

I can get a true mirror polish with my Naniwa 12K, but the edge is tends to be somewhat harsh with some steels. That is why I tried the Tsushima blue. The edge might not be as sharp, but it is more smooth.

I am anxious to see what kind of results others who have indicated they plan to purchase the stone will be able to achieve. This stone is not going to replace Eschers, Coticules, and Nakayamas, but for those who do not want to pay the exorbitant asking prices for these stones, the ocean blue may be an alternative. Yes, I could have purchased a Coticule bout for a similar price, but I would rather have a rectangular stone.

Sometimes it seems that a stone that does one or more things really well, when it comes to the final sharpening stages of finishing off a razor, command a premium price. Especially the ones that are known to.

Originally Posted by RayClem

The large ocean blue stone I purchased was 7 3/4" L x 2 11/16" W x 15/16" thick with all measurements to 1/16". The weight was 949g.

Perhaps they are changing the description with each stone they sell? I dont know. Its odd.

Originally Posted by Magpie

Perhaps they are changing the description with each stone they sell? I dont know. Its odd.

I think it's probably more likely that they aren't all cut to the same exacting spec.

Having had an Amazon gift card burning a hole in my pocket for a while now, I decided to try an 'L' version of this stone. It arrived this morning. I have only had a few minutes playing with it so far - enough time to flatten it and run a couple test razors and a knife over it a bit.

Some observations: The stone is fairly hard but not crazy hard. I'd put it at around 4.5 hardness level on the commonly used 1-5 JNat hardness scale. Used with diamond plate generated slurry the edge produced is nowhere near what a 12k synth produces IMO. I'd put the edge produced closer to that 4-6k mark like the more common black Tsushima stone. Looking at the surface of the stone under a 10x loupe side by side with a Thuri, the Thuri is visibly considerably finer. I'm not absolutely convinced this is an actual JNat. I'll withhold a verdict on that for now though. The stone has a lot of "sparkles" on the surface as well, which none of my other JNats have.

That said, on straight water it produces a very high polish, and the feedback is quite good - the feel smooths out until it feels like oiled glass under the blade as it ceases to do much cutting. When slurry honing the slurry definitely darkens a good bit, and the characteristic "steely" smell of swarf is very clear.

The stone shows a quite burnished surface where the razor made contact when honing with straight water. Slurry honing with the included tomonagura-generated slurry produces a finer finish than DN generated slurry, as would be expected. The stone does not appear to auto-slurry very much, and can be readily diluted out to straight water, unlike the black Tsushima I've used.

So anyway, just a quick preliminary report. I will do some more work with the hone in the next few days and probably take a few scope photos for comparison to some of my other JNats as far as scratch depth and pitch using my reference razor (I have used this razor for a long series of scope images so that the only variable is the hone - probably have 50 or so by now).

I got my hone today (the small one). I honed a couple of razors that were finished on Cnats and I'll shave with them over the next few days and see if I can tell anything about the edge over a Cnat edge.

Originally Posted by gcbryan

I got my hone today (the small one). I honed a couple of razors that were finished on Cnats and I'll shave with them over the next few days and see if I can tell anything about the edge over a Cnat edge.

Thanks. Now this is getting interesting.

Thanks eKretz. You obviously have a lot more experience honing than I do, so I value your comments. I look forward to your microphotographs. My objective in starting this thread was to foster conversation and I have certainly succeeded in that.

After going back and honing a razor on my Naniwa 12K SS and then taking it to the ocean blue, I did note that the edge was more polished on the 12K and became more hazy on the natural. I used the matching nagura stone to create the slurry, so it was still polished to the naked eye.

Although I like the shave from the 12K synthetic on most of my razors, it creates a harsh edge on my Hart with O1 tool steel. The natural stone produces a smoother, more comfortable edge.

If I recall correctly, I believe Coticules are often quoted as 6-8K stones, but they finish well when starting with a slurry and finishing on water. They may not produce the sharpest edge, but produce a smooth edge. I think the ocean blue may do something similar, at least with some steels.

One day, I will probably purchase a Coticule. They are pricey enough, especially for a rectangular stone. I would love to have a Thuringian as well, but they are even more expensive, especially if it is a real Escher.

Right now, I am spending my money on razors. I have a Jerry Stark custom coming in the mail later today. After I add a couple of more razors to my collection (likely a Wacker and a Brian Brown), maybe I will go back to buying hones. It is difficult to support both a razor addiction and a hone addiction at the same time.

Originally Posted by eKretz

The stone has a lot of "sparkles" on the surface as well, which none of my other JNats have.

I have seen Jnats with sparkles, I think I still have one of those. It is not too common thing though.


Regarding the Tsushima, I pointed out earlier that if it is indeed Tsushima it will be in the midrange. The color looks off as well. Might be a marketing thing, or it is a just a variety that we have not seen by now. I have not seen anything but dark Tsushima in Japan though.

Just to add a note to my last post, my (smaller) stone doesn't have a slurry stone and I used it only with water.