Thread: Stone hardness & decription questions

So first off. This was sold as a Narutaki Akane Tomae 4+. I am confused on the hardness of this stone first off. Initial feel and water tests say this is more of a 5 or more in hardness. Water sits on it forever. No self slurry with knifes or razors, but produces a good bit of swarf so it has good speed. Once I use a tomo though it produces slurry very easily and also with atoma lapping plate. So on water only it seems like a 5 to 5+, but when slurrying it seems like a 4 or 4+. Never had a stone like this before how would one gauge the hardness better?

Next I still have only seen very few stones listed as Akane or Akane iromono and seem to feel this would still just be an Iromono Tomae, but is there a difference?

Finally in the pics you may be able to see small purple dots that cover the stone. Are these Nashiji, goma or renge? Nashiji I thought was mostly on Kiita stones, Goma I thought are usually black and renge is usually on Suita stones. This is a red stone with purple spots.

So… How is the edge?

Hardness/fineness is an estimation by the user/seller based on his experience and the performance of the stone.

It is a natural stone, so there are no absolutes.

That you feel it is harder/ finer, is a good thing, no?

As with most things now, that market is shrouded with mystery as to the provenance of ancient stones, and you/we are at the mercy or graced by the expertise and voracity of the seller.

All natural stones are a roll of the dice, in terms of performance, but a good guide can make the journey smoother and more successful. It sounds like a stone you have room to grow into…

Nice looking stone, enjoy.

The edges are awesome and the stone is very fine. I just never had one that I couldn't figure a good hardness for. It is usually one way or another this stone just seems to have both.

Took a shot with the loop and phone to try and show the purple spots.

Originally Posted by rideon66

The edges are awesome and the stone is very fine. I just never had one that I couldn't figure a good hardness for. It is usually one way or another this stone just seems to have both.

I understand your desire to assign it a number, but it sounds like a great hone.

Originally Posted by Utopian

I understand your desire to assign it a number, but it sounds like a great hone.

You are correct. I just want to satisfy my own understanding and knowledge.

Well if it bothers you that much get one of those hardness kits they sell in science and education stores and test it yourself. They are just a few bucks and you'll know for sure.

I think when you are buying a Japanese natural stone, you need to be clear on what you tell the vendor you want or what you intend to use it for. I think retailers that grade stones that are still stamped are guessing a bit, based on the mine it came from and its strata/colour. I can only comment about my own experience, but I looked for stones that would be for final finishing/polish of straight razors. I asked exactly that and now after using the stones, I got what I wanted. I think that a stone that readily produces swarf in the slurry isn't a super hard stone, it is faster and more abrasive, which leads one to think it would be unlikely to be a perfect finishing stone. Now I may be wrong, but the Ozuku I bought does not give up swarf to any great degree, but under 400x power the pattern on the bevel/edge is what you would expect and want (Kasumi).
IMHO assigning a hardness level, is a bit like guessing a grit rating. That hardness scale often touted as a guide to the usefulness of the stone, tends to be more for the buyer to relax about the choice of hone. Natural stones can't be assigned like that. So, be very clear to the vendor, and most of the time you will get a good result, especially if you trust the vendor. Buy from reliable vendors, and enter into the purchase with open eyes, as its not a clear cut thing. Just a thought.

Originally Posted by bobski

I think when you are buying a Japanese natural stone, you need to be clear on what you tell the vendor you want or what you intend to use it for. I think retailers that grade stones that are still stamped are guessing a bit, based on the mine it came from and its strata/colour. I can only comment about my own experience, but I looked for stones that would be for final finishing/polish of straight razors. I asked exactly that and now after using the stones, I got what I wanted. I think that a stone that readily produces swarf in the slurry isn't a super hard stone, it is faster and more abrasive, which leads one to think it would be unlikely to be a perfect finishing stone. Now I may be wrong, but the Ozuku I bought does not give up swarf to any great degree, but under 400x power the pattern on the bevel/edge is what you would expect and want (Kasumi).
IMHO assigning a hardness level, is a bit like guessing a grit rating. That hardness scale often touted as a guide to the usefulness of the stone, tends to be more for the buyer to relax about the choice of hone. Natural stones can't be assigned like that. So, be very clear to the vendor, and most of the time you will get a good result, especially if you trust the vendor. Buy from reliable vendors, and enter into the purchase with open eyes, as its not a clear cut thing. Just a thought.

Oh I have no problem with the stone or it's final finish. The edges are excellent smooth and one pass cleared. Now I usually do 2-3 just so I do wtg and atg. I think the wholesaler or seller may have a good estimate on the hardness based on the properties. It just seemed harder to quantify to me because all other stones I have had went one way or the other. I also base my judgement from multiple other stones I have purchased from reputable sellers and based on their hardness assessment I am able to come up with a good idea of range for these stones. This one just feels harder with water only than it is and softer with slurry than it is. So I think they put the rating in the middle based on that. Now with stone speed and fineness I think a stone should have decent speed (swarf should come up in water only), should be hard enough that is should not self slurry with a razor water only and some pressure plus should be fine enough to finish a razor. That being said we all have different skin types and preferences. I tend to not like the edges from super hard stones as much . I do have some and get very nice edges, but tend to like the edges from stones that would be more in the 4+/5 range. Ultimately I do not fully believe in hardness being a factor in finishing. I think it has more to do with how fine the stone is and how it gives up new particles to sharpen and finish. So in my view if a stone does not self slurry and has great fineness you can refine and polish an edge just as well as a super hard stone and to me the edge is smoother and more gentle to my sensitive skin. I have even found with the right touch you can produce a very nice edge with even the softer of stones if the fineness is there and it isn't constantly giving up new particles with a super light touch. It is similar to the touch one would need to finish an edge properly water only on a super hard stone.