Thread: Jnat experts wanted: what do I have?

I bought this hone about 15 years ago from a woodworking store. It was sold to me as a very fine finishing stone. The box has no markings other than “Karasu 10�. I know that Karasu means crow in Japanese and refers to the pattern, not the type of stone as far as I know.

Does anyone know what it might be?

As far as the stone is concerned, it is very hard, and it takes a long time to raise a slurry with Nagura. Some razors seem to respond well to being finished on it, but others less so. Even after all these years, i am still figuring this stone out. Perhaps I need the right tomo nagura for it?

Can you post a good image of the ‘skin’ on the bottom edge in the first image?

On those hard stones a 1200 Atoma or equivalent DMT to creat a slurry is a great way to start after you set the bevel. Then finish with your tomo.
Great looking stone by the way!

Here is the skin, only visible on one side:

The skin is not on the bottom of the stone? Nly the sides?

No expert here. Anyway looks like both sides may be usable. Carpenter shop may indicate it is a tool stone but no way to find out till you find out. This is how i test stones, not the only way or best way its just what i do. Take a razor and do a slew of half strokes on it. Then i take wipe it with a white paper towel and see if it self slurries. The stone color is what you would see. Then I would take a razor and look at the scratch patterns to see how course they appear, water only, then with slight slurry from a diamond plate. Some karasu are scratchy. Finish a razor to 12k or so with a synthetic stone and then see what that stone does to that edge in a shave test. I would use a diamond plate generated slurry about the size of a quarter and see. Do that and test shave it.

That’s right! The two sides are pictured in my first post.

Well, the skin didn’t help much, but it was worth a tey. There aren’t any sparkly black patches on the skin are there?

Judging by the color and hardness, it may well be from the Ozuku mine (just a wild guess). It's a finishing stone - that's all that matters. Looks good to me in terms of the surface - nice and clean.
Hope you can unlock its secrets!

Originally Posted by Steve56

Well, the skin didn’t help much, but it was worth a tey. There aren’t any sparkly black patches on the skin are there?

No sparkly black patches, no.

I just gave this stone a good try again, as it has been on my mind. I dulled the edge of my old beat up Henkotsu kamisori on a glass, and took it to this stone. I used slurry from a Tenjou and Mejiro nagura consecutively, thinning the slurries as I went along. Then I stropped it 30 laps on linen, gave it 10 laps each on balsa with 0.5 and 0.25 micron diamond paste. Then 10 more laps on linen, and 40 laps on leather. Result: a really keen edge - I wonder if with the stone's own slurry, or a suitable tomo nagura, I'd be able to leave out the pasted balsa strops altogether.