Thread: What is Grit in Japanese Natural Stones, and How Important Is It.

Everything on the earth gets recycled. All the rock is weathered and then washed into the seas and then gets re-manufactured into rock again and the cycle goes on and on. What makes some rocks different is just happenstance. The right combination of minerals under the right conditions. I remember years ago during a geology Field trip going to Franklin, N.J which is a very famous locality for a vast assemblage of fluorescent minerals and had a variety of iron, manganese and Zinc Minerals. It sits on a hill and you can look across a broad valley to a ridge across which is Stirling Hill and both locations have these minerals. Most of the economically valuable ore went between the two and it was all weathered away leaving these two "tiny" legs left over.

I am looking for 2 straight razor users to come to Sonoma for a honing session to act as independent participants. I believe that I can prove that the grit from Japanese tennen toishi is as fine or finer than a Shapton 30k stone.
I will provide a 600x microscope for all of us to use, I have a Shapton 30k on glass stone, of course a few stones to play with, and lunch.

It would be helpful is one of the users has a video camera, HD prefered and knows how to use it, and a seperate Shapton 30k. If those fellows or gals who can come do not have either of those items, maybe they can borrow, beg or steal the items.
Professional sharpeners welcome as well as observers. I have a dedicate shop.

In the past a few of you have been to my shop and you know I love to sharpen for hours and hours and hours. So those who can come be prepared to spend the better part of a day here.

Because I am self employed almost any day of the week will work although Sundays - Thursdays are best.
No reason not to communicate through this thread. best wishes, Alex

It would be very interesting to see the results of this honing session! With text and hd video even better there a lot of people on here interested in j-nats and how to use them.

Obviously there's more to these curious and varied natural stones than meets my eye, and I am continuing to learn as I go along. Two points have come to the forefront for me that deserve some acknowledgement.


The first would be the hardness issue. Thanks to Jim Rion, Maxim & Stefan and others, I am now backing the use of ultra hard stones for razors in the finishing process. On my website I will set aside the LV5 & LV5+ stones for razors in a similar manner as Maxim does while providing the softer stone to knife and tool users. It just makes sense to use the bound-up grit in these very hard stones as the base for finishing razors. I have used the clear water stage in my final honing progression for some time, I now see the logic behind the hardness factor of bound up grit in the earlier stages of the progression as well.



My second realization regards the fineness factor in awasedo. The illusive 30k or greater grit particles in japanese awasedo has proven difficult to document. This will require a greater skill than I most likely will ever possess. So for now it will remain anecdotal. I still believe that some grit particles in awasedo will polish to finer levels but, the problem remains of how to isolate them. And because it is so difficult to isolate them, this very state of illusiveness appears to diminish their importance.

In a slurry situtation I have found that the japanese hon yama stones continue to cough up a greatly varied selection of particle in the obvious sizes, those most easily seen as scratches likely in the 2-3um range. In use, the continous outpouring of particles places the ability of isolating and documenting the finest of the fine an extremely difficult quest. If one were to suppose that grit from awasedo did deminish in size under labor, what prevents it from becoming smaller under additional labor? I found myself at the short end of the curve, a place where the finest of the fine fall through the cracks in regards to my home based documentation scheme and are never seen from again because they just get smaller. My latest attempt was based on harvested slurry which was then dried and utilized as grit on a pasted strop. The grit just blew away.

Furthermore, even if I could show the break down, in reality what part does the ultra fine grit play in honing, when at all stages fresh large full size particles emerge and come into play overshadowing the smallest particles effects on the blade?

The idea that multiple sizes of grit working together in unison will create a vast and complex web of scratches and peaks that act in a naturally harmonious systematic way to develop triangulated structures within groups of scratches at the razors edge, will remain with me just a theory for the time being. best to all, Alx

Originally Posted by alx

Obviously there's more to these curious and varied natural stones than meets my eye, and I am continuing to learn as I go along. Two points have come to the forefront for me that deserve some acknowledgement.


The first would be the hardness issue. Thanks to Jim Rion, Maxim & Stefan and others, I am now backing the use of ultra hard stones for razors in the finishing process. On my website I will set aside the LV5 & LV5+ stones for razors in a similar manner as Maxim does while providing the softer stone to knife and tool users. It just makes sense to use the bound-up grit in these very hard stones as the base for finishing razors. I have used the clear water stage in my final honing progression for some time, I now see the logic behind the hardness factor of bound up grit in the earlier stages of the progression as well.



My second realization regards the fineness factor in awasedo. The illusive 30k or greater grit particles in japanese awasedo has proven difficult to document. This will require a greater skill than I most likely will ever possess. So for now it will remain anecdotal. I still believe that some grit particles in awasedo will polish to finer levels but, the problem remains of how to isolate them. And because it is so difficult to isolate them, this very state of illusiveness appears to diminish their importance.

In a slurry situtation I have found that the japanese hon yama stones continue to cough up a greatly varied selection of particle in the obvious sizes, those most easily seen as scratches likely in the 2-3um range. In use, the continous outpouring of particles places the ability of isolating and documenting the finest of the fine an extremely difficult quest. If one were to suppose that grit from awasedo did deminish in size under labor, what prevents it from becoming smaller under additional labor? I found myself at the short end of the curve, a place where the finest of the fine fall through the cracks in regards to my home based documentation scheme and are never seen from again because they just get smaller. My latest attempt was based on harvested slurry which was then dried and utilized as grit on a pasted strop. The grit just blew away.

Furthermore, even if I could show the break down, in reality what part does the ultra fine grit play in honing, when at all stages fresh large full size particles emerge and come into play overshadowing the smallest particles effects on the blade?

The idea that multiple sizes of grit working together in unison will create a vast and complex web of scratches and peaks that act in a naturally harmonious systematic way to develop triangulated structures within groups of scratches at the razors edge, will remain with me just a theory for the time being. best to all, Alx

Alex, your point about new particles overshadowing the smaller particles is valid, but that is
exactly why a very hard stone is the best choice as the ultra hard stones will (almost)not
release any grit.

I think what happens when a very hard natural stone does ''shed'' its grit, the grit breaks
rather than it getting released from its binder. So while the sharpening particles in jnats
are about 3 micron, the broken off grit particles are smaller than this I am guessing. The
harder the stone, the less likely it will shed/release its own sharpening particles with the
added advantage( I am guessing here) that the jnat grit are , which are flakes actually
get broken as they are released, so you don't get new 3 micron sharpening particles,but
smaller ones.

About hardness rating, 330mate has a max of LV5++++, metalmaster uses LV5.5 which
he recommends for razor sharpening. There are no real ways to ''calculate'', measure
hardness AFAIK in Jnat's. Some say you cannot compare hardness between different
type of stones, like a coticule or guangxi hone with a Jnat. I disagree, hardness is hardness.

For example my guangxi hone which cost me 15 bucks is almost as hard as my hardest ozuku
It's true that a very hard guangxi hone can be less fine than a softer jnat, so in that regard
they cannot be compared hardness and finess wise, but stricly hardness wise all stones can
be compared.

Alex if I can suggest something to you. Take your hardest stone, create a slurry on it with
a tomonagura. Then sharpen your plane blade(microbevel) on it for about 2 minutes. Every 10
seconds or so create some new slurry with your tomonagura. Finish off by making new slurry and
sharpen your plane blade for just a few seconds. Now take a picture of the edge. This will
show the result of sharpening on fresh slurry. Now do the same thing again, but only create slurry
once with your tomonagura and keep sharpening your plane blade with this same slurry for
a minute or two. Stop and take a picture of the edge. This way you can prove that the slurry
does indeed breakdown as the edge should be better the second time because the grit
breaks down to finer particles whereas in the first test you keep introducing new slurry which
doesn't allow you to get the best finish.

I would suggest that you use a plane blade which has steel comparable to kamisor, straight
razor steel. I think japanese plane blades have very hard steel which could be a factor in
releasing new grit constantly whereas the softer kamisori steel can't do this.

Sharpman

Originally Posted by SharpMan

Alex if I can suggest something to you. Take your hardest stone, create a slurry on it with
a tomonagura. Then sharpen your plane blade(microbevel) on it for about 2 minutes. Every 10
seconds or so create some new slurry with your tomonagura. Finish off by making new slurry and
sharpen your plane blade for just a few seconds. Now take a picture of the edge. This will
show the result of sharpening on fresh slurry. Now do the same thing again, but only create slurry
once with your tomonagura and keep sharpening your plane blade with this same slurry for
a minute or two. Stop and take a picture of the edge. This way you can prove that the slurry
does indeed breakdown as the edge should be better the second time because the grit
breaks down to finer particles whereas in the first test you keep introducing new slurry which
doesn't allow you to get the best finish.

I would suggest that you use a plane blade which has steel comparable to kamisor, straight
razor steel. I think japanese plane blades have very hard steel which could be a factor in
releasing new grit constantly whereas the softer kamisori steel can't do this.

Sharpman

Sharpman, thank you for your detailed imput. You suggestion duly noted, and test results forthcoming.

Can you clarify one point, you mentioned in the same sentence the terms "very hard" and "ultra hard",

"Alex, your point about new particles overshadowing the smaller particles is valid, but that is
exactly why a very hard stone is the best choice as the ultra hard stones will (almost) not
release any grit".

Should we infer a distinction here? Alx

Originally Posted by alx

Sharpman, thank you for your detailed imput. You suggestion duly noted, and test results forthcoming.

Can you clarify one point, you mentioned in the same sentence the terms "very hard" and "ultra hard",

"Alex, your point about new particles overshadowing the smaller particles is valid, but that is
exactly why a very hard stone is the best choice as the ultra hard stones will (almost) not
release any grit".

Should we infer a distinction here? Alx

Alex, no distinction, was a bit tired when I wrote the reply. Basically the harder
the stone, the less quick it will release its own grit and the smaller the grit
will be when it is released. I know that it was mentioned that the grit particles
are the same in all jnats, around 3 micron, but my thought is that the harder
the stone the smalller the ''released grit particle'' will be as the grit isn't actually
released in its real size, but actually broken off. Think about Arkansas stones,
the hardest arkansas stones are the finest, but they have the same grit particle
as the softer, coarser arkansas stones.

Sharpman

Very interestind thread. I have a couple question which may sound very naive but I will mention it anyways.

1-why can't you make up some slurry using diamond plate or tomo nagura or whatever and pour it on some indestructible surface that releases no slurry, and hone using only the slurry? basically the base has nothing to do with honing, you just use the slurry. this way there is no contamination of new slurry getting introduced to the mix.

2-if you are trying to use the finest possible jnats and you don't want large chunks of slurry, why do people commonly use DMT 600 instead of much much finer diamond plates available from DMT?

Alex I am still tuned in to see what happens at your shapton 30k vs jnat experiment.

Dan

Originally Posted by danielghofrani

Very interestind thread. I have a couple question which may sound very naive but I will mention it anyways.

1-why can't you make up some slurry using diamond plate or tomo nagura or whatever and pour it on some indestructible surface that releases no slurry, and hone using only the slurry? basically the base has nothing to do with honing, you just use the slurry. this way there is no contamination of new slurry getting introduced to the mix.

you need to have the friction with the base stone for the slurry to break down

2-if you are trying to use the finest possible jnats and you don't want large chunks of slurry, why do people commonly use DMT 600 instead of much much finer diamond plates available from DMT?

Dan

The finest slurry can be made with tomonagura, as far as I know in Japan they do not use diamond plates for slurry.

The finest slurry can be made with tomonagura, as far as I know in Japan they do not use diamond plates for slurry.

sure but for the folks who DO use the diamond plates: why don't you use the finer ones? DMT makes 8k level diamond plate