Thread: Tsushima "Ocean Blue" 12K

I recently purchased a Tsushima "ocean blue" Japanese 12K natural sharpening stone. There is also a Tsushima "ocean black" stone, but I think it is lower grit stone more suitable for mid-range honing after setting the bevel. The "ocean blue" is a finisher.

Do any of the other SRP members tried using this stone for razors? If so, please relate your experience with this stone.

Supposedly it comes from a recently closed underwater mine in South Tsushima Island. Because the stone was mined until recently and is more available than some of the JNATs that came from mines closed decades ago, the price was reasonable, but is not a cheap stone.

The stones are available in a variety of sizes; I purchased a 8.0" x 2.7" x 1.0" stone that is an ideal size for razor honing. It comes with a matching Nagura in a leatherete case.

https://www.amazon.com/Natural-Sharp.../dp/B01CMY2HA2

I was only able to find a couple of reviews of Tsushima stones on YouTube, both by Robert Ortiz. I think one is on the ocean blue and one is on the lower grit ocean black.

The stone seems to be exceptionally uniform in structure, no inclusions, cracks, layering, etc. It was lapped on all sides. Although it is impossible to assign a true grit rating to a natural stone: by feel, under a 30x magnifier and by honing scratch pattern, I have no doubt that the stone I received is 12K or higher. I have both a C12K and Naniwa 12K SS for comparison. Some of the reviewers of the stone loved it and others thought it was a lower grit stone, but the one I received seemed to be 12K.

I used the new stone to refresh a couple of razors that weren't quite giving as good a shave as I wanted and found that it did improve the edge, both under the microscope and on my face. I created a slurry using the Nagura, started with circles and finished with water and X-strokes. As the edge gets polished. the stone get quite sticky.

I will have to do a lot more experimenting before I can tell you whether the Naniwa 12K, C12K, or Tsushima "Ocean Blue" 12K give the best edge on the majority of my razors, but for now, I am pleased with this addition to my tool kit.

This a natural stone, therefore grit rating is absurd as they do not have one.
Tsushima behaves close to 4-6k stone (variations are common for J-Nats), the 12k is just a buzz word to attract buyers.

The recently closed mine claim is a new thing to me, but it could be true. That stone can be used for a bridge from 1k to a finisher, or for knives.

Originally Posted by mainaman

This a natural stone, therefore grit rating is absurd as they do not have one.

Thank you!!!

Originally Posted by mainaman

This a natural stone, therefore grit rating is absurd as they do not have one.
Tsushima behaves close to 4-6k stone (variations are common for J-Nats), the 12k is just a buzz word to attract buyers.

The recently closed mine claim is a new thing to me, but it could be true. That stone can be used for a bridge from 1k to a finisher, or for knives.

As I said in my original review, it is "impossible to assign a true grit rating to a natural stone". However, I have a complete set of Naniwa new superstones. In comparing the surface of the stones, my Tsushima ocean blue is significantly finer than my Naniwa 5K, 8K, and 10K superstones, and as good or better than my Naniwa 12K. Thus, at least with my specific stone, I believe 12K to be a reasonable description. My stone is much finer than the 4-6K rating you surmise.

There may well be Tsushima stones that are similar to 4-6K synthetics. I understand that there are stones from that same mine that can be used as prefinishers, but are not fine enough to be used as finishers. The stone I received, however, is ultra-fine and definitely suitable for finishing.

If someone else were to purchase another stone from the same source, it may or may not be as fine as the one I received. That is the risk you take with any natural. You have to trust the vendor to rate the stones appropriately. I took a chance on the vendor of Tsushima stones and was rewarded.

Originally Posted by RayClem

As I said in my original review, it is "impossible to assign a true grit rating to a natural stone". However, I have a complete set of Naniwa new superstones. In comparing the surface of the stones, my Tsushima ocean blue is significantly finer than my Naniwa 5K, 8K, and 10K superstones, and as good or better than my Naniwa 12K. Thus, at least with my specific stone, I believe 12K to be a reasonable description. My stone is much finer than the 4-6K rating you surmise.

There may well be Tsushima stones that are similar to 4-6K synthetics. I understand that there are stones from that same mine that can be used as prefinishers, but are not fine enough to be used as finishers. The stone I received, however, is ultra-fine and definitely suitable for finishing.

If someone else were to purchase another stone from the same source, it may or may not be as fine as the one I received. That is the risk you take with any natural. You have to trust the vendor to rate the stones appropriately. I took a chance on the vendor of Tsushima stones and was rewarded.

I was referring more to what the listing says not you, I hope I did not offend you. What I said about Tsushima is based on what the common perception about the stone is. In Japan, those stones are sold as knife stones, not razor stones. There is a reason for that, they are not fine enough.

Yes, they are considered knife stones, nice to look at though.

You can, on some naturals compare the stria pattern, to a known grit synthetic stone, not by feeling it, but by honing side by side with both stones on the same steel.

Many low grit stones feel smooth, but the grit size is what does the cutting, not the feel of the stone face. A good example are barber hones, many feel very slick, but are very aggressive and leave deep stria patterns.

With many Jnats, they do not leave a uniform synthetic stone stria pattern, that is part of their appeal. As a result, they cannot be grit compared.

Hone a razor with a synthetic 12k, then mark the half way point between the heel and toe on the razor. Now hone the toe end, on the Natural, keeping the marked line on the edge of the stone.

Now compare the stria from one end to the other, especially where they meet.

I have a black not a blue, and it does produce a nice knife edge.

I have some Tsushima black nagura and indeed, it's a mid range stone. I used to use it more in the past, now not so much anymore... This ocean blue looks like it's a different stone to me. It's probably too soon to tell exactly what it's capable of, but sounds interesting... I wonder how it compares to the black Tsushima in hardness. Does your stone auto-slurry visibly? Could you describe the honing feeling on slurry? Do you hear much hiss and does it go away as you hone on it?

When I compared the Tsushima to my Naniwa stones, not only did I examine the surface of the stone by feel and under a 30X scope, but I also examined the edge of the two razors I honed on the stone using a USB microscope. The scratch (stria) pattern on the Tshshima ocean blue is as good or better than the Naniwa 12K.

Please do not think that because an "ocean black" stone is not a suitable finisher that the "ocean blue" will not be. That is like comparing a Belgium blue to a Coticule. They both come out of the same region, but they are different stones. I do not have an "ocean black" but if I did, from what I have heard, I would not try to finish on it.

My Tsushima blue is ultra fine, of uniform consistency, very hard and dense, just as described by the vendor. I understand those are characteristics desired for a good natural finisher for razors.

I admit that my experience with this hone is limited. I have only tried to finish two razors. However, those two razors have been problematic. I could never get a suitable edge on either of them with either a Naniwa 12k new superstone or a C12K. Although I could get both of these razors to the point they would shave, the shaves were harsh. That is why I was interested in purchasing another natural stone. After finishing on the Tsushima ocean blue, both edges are improved beyond that which I was able to achieve previously. As I get to know the stone better and refine my technique, I suspect I will be able to achieve even better results.

When I started to use my Tsushima blue, I dipped the stone in water. The stone is very dense, so it does not absorb much water.

Although the stone was already lapped on all sides, I lightly lapped the surface of the stone I planned to use for honing. I then created a slurry with the matching Nagura stone. The stone is quite hard, so I doubt you get much in the way of additional slurry as you hone on it. The slurry is similar in color to the color of the fine metalic shavings, so it is difficult to tell how much metal is being removed. With the hardness of the stone, I suspect the slurry breaks down into finer particles as you hone.

Since the razors I finished had already been honed on other stones, including Naniwa 12K and C12K stones, little metal was removed and there was not a lot of audible feedback. I started with circles and then switched to x-strokes. As I started to thin out the slurry with water and the edge became more polished, the stone started to become "sticky". In the future, I might try to add a lubricant such as glycerin to minimize the stickiness and see if I can get even a smoother edge, but for now these are the best edges I have been able to get on these two problematic razors.

You want to compare stria size, if possible. It is smaller, thicker or the same.

I was watching a recent auction on the blue stone, and the seller was hyping the stone, unabashedly quoting grit sizes, which for me is a red flag about the seller.

These stones are not new and traditionally, they have not been razor finisher.

There is a lot to learn using naturals, Jnats are no different, it can be a windy road.

If you are having trouble getting an edge on a Naniwa 12k, moving to a natural just invites a host of variables. It is not uncommon for results to be lacking on the Chinses stone, few if any are 12k, or close.


Enjoy.