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

Originally Posted by danielghofrani

While I am no expert at this, I wonder if the polish of the bevel has much to do with the sharpness/smoothness of the edge. I had a near wedge razor that was honed with no tape and the bevel was wide and absolutely mirror, but shave was only mediocre. I had a razor honed by Stefan whose bevel had a sandblasted look under the loupe (finished on jnat BTW) but extremely sharp and smooth.

Daniel

Sharpness is a relative notion, and if I may be so bold, the degree of sharpness can beyond a certain point be both relative and redundent. Relative as to what type of beard that is being shaven, and redundent as to how much sharper does the blade need to be beyond that which is established (for that particular beard) as to be sharp enough.

The granular structure of steels vary from one blade to another even within one maker or makers line, and there is a limit as to maximum degree of sharpness that a blade will accept while still maintaining a degree of structural integrity. If you go beyond that limit the blades edge breaks down prematurely through normal use, thereby making the blade redundent or useless until it is rehoned.

A lot of us here are hobbiest honers, serious shavers indeed but hone as a hobby. Got the itch to hone, try out a new hone, hone while my wife is at work, etc. How many here rehone a blade after just 2 or 3 shaves? A touch up with a diamond spray is considered a honing, a touch up with a barbers old style or a natural Ark or Jnat is considered a honing. Stropping with a charged linen or leather strop is honing if an abrasive was intended and added on to the strop in order to improve the edge.

How long and for how many shaves should an edge hold up? If it is less than 20 than I would say that the edge is being over honed and is too thin at the edge if it breaks down that quickly. Here is where the craft comes in, with the user crafting an edge that suits the beard and the steel by using the abrasives with skill and forethought. If you were a professional barber 50 or 100 years ago you would probably open your shop each morning with at least 2 razors fully honed. Imagine shaving 30 or 40 dirty off the dusty street faces each day, your edges better be holding up for you to get and maintain repeat business. With that traffic you surely do not have time off to sit down for 45 minutes to rehone a razor with customers waiting. As a hobbist we can afford to indulge ourselves in weak edges, but are we all not looking for that Barber Type Shave, which are by definition edges that are not only sharp enough but hold up well from day to day.

My beef here is that a product is being sold as an idea and touted as a proven and accepted idea. A shiny and bright blade is sharper indeed, but at what cost. A high polished blade is sharper, but for how long. And how sharp does a blade need to be beyond a certain point without bragging rights snuggling in somehow and taking over the conversation.

For how long an edge holds up when honed by a hobbist is a personal choice and to each his own, but for trends to be promoted in such a rigid direction is in my opinion stunting the development of the creative use and developments of edges that are appropriate for the particular use at hand.

The craft topic, the manual labor, the do it yourself at home, the skill topic here is creating the balance between how sharp and for how long. If bright or chrome or matte or sandblasted finishes work, whatever the preference. My personal goal is not the apparently perfect sterile factory finishes that pastes or sprays provide, those are too perfect and too easy to buy out of a bottle. I long for the inventiveness that natural stones demand, the all important failures followed by the joyous succsses.

The beauty of natural stones is that they themselves are just imperfect enough to demand the burden upon us to be more perfect in learning to use them. Alx

Good Post ALX...well said!

I still haven't seen the proof that a jnat can actually finish in the 30k
range.

Alex you wrote that you tried slurry on plate glass and you saw/felt
the grit getting smaller and smaller. So where are your pictures with
the results?

Sharpman

Originally Posted by SharpMan

I still haven't seen the proof that a jnat can actually finish in the 30k
range.

Alex you wrote that you tried slurry on plate glass and you saw/felt
the grit getting smaller and smaller. So where are your pictures with
the results?

Sharpman

Hello Sharpman
Thank you for reminding me about some "proof" as you say. I am in Japan right now as of April 25th, but I did take some photos before I left that might help to continue this topic. I hope others will try to do a better job on this and maybe further the simpleton manner in which I work.

I have found it very difficult to record the polishing effect from a Jnat in the past but I think I stumbled upon a couple of ideas that might work to explain why a high grade Jnat gives such a good shave. First off the manner that Iwasaki suggested requires a lot of time and strokes to polish the whole blades bevel. For photographic purposes I chose to polish only a very narrow area just at the razors edge and it made the work more accurate and quicker. This concentrated the effort where it could be seen in my microscope at the razors edge which is really the only place where it actually matters as far as shaving goes, cosmetics aside. The old idea of taping the spine does just this as we all know, it lifts the spine so the angle approach concentrates on the forward edge area.

Secondly I use clear running water when using the Nakayama, this all but eliminated any slurry formation that would certainly introduce new fresh grit particles. This idea dawned on me because of the lack of grit released with the Shapton 30k on Glass stone when using it. All of the grit in the Shapton is bound up firmly in the stones matrix through some amazing technology, so in this way only the top surface of the stones grit comes into contact with the blade. I mimiced this same bound up grit action with the Nakayama #484 by keeping the stone rinsed. Anyway here is a group of photos to begin with. I have another set of photos if anyone is interested. I hope this helps, Alx

This is my "Post of the Year" candidate, thank you Alx.

"My personal goal is not the apparently perfect sterile factory finishes that pastes or sprays provide, those are too perfect and too easy to buy out of a bottle. I long for the inventiveness that natural stones demand, the all important failures followed by the joyous succsses.

The beauty of natural stones is that they themselves are just imperfect enough to demand the burden upon us to be more perfect in learning to use them."

Grit - is a term that, while important for a baseline understanding of an abrasive process, is short on being a comprehensive point of consideration. Grit usually refers to some kind of average particle size, and the particle in question would be the abrasive particles. There are other particles present also; binder, matrix, etc. Do those non-abraive particles factor into the equation somehow? I believe they do, in some kind of mechanical way. They don't remove steel but I beleive they allow the abrasive particles to work in one way or another.
To isolate the abrasive particle in a natural stone would be an interesting process to say the least. Japanese stones used for honing - along with many others - started their 'life' out as silt. Silt being a combination of things. That silt becomes, shale, then slate, and over time schist. There are other steps and possibilities, so that's just a brief overview.
Many of the hones we call Jnats, I believe, belong to the slate family. I don't believe their makeup is all that homogenous. The abrasive particle size, what we may reference as the stone's 'grit' is therefore - somewhat nebulous. Not to mention the rest of what makes up the stone - I believe this to be where a good part the Jnat mystique lies.
How fine can any stone's particles break down under 'working' conditions with a Razor? I don't know - I'm not certain that it matters either, but for the sake of edified discussion I think it might be a starting point. At what point does a broken-down particle cease to have any cutting ability? Certainly there must be a limiting factor here. How can we prove that?
Again - I don't know. Someone involved in metalurgy might be able to chime in but I suppose there are many many variables that need to be sorted out first. For example - does particle X have the same impact on steel Y as particle Z does on steel Q?
The puzzle grows with each identified variable.
I wonder - if one has a Jnat, we'll call it 'Stone X' that we know has abrasive particles that are more coarse than those found in 'Stone Y' - can one expect that with additional working of the slurry, we might wind up with broken-down particles that equal the size of those found in Stone Y's slurry?
How fine can we go - how keen an edge can the steel handle, how does pressure factor in, and so on... there are a bunch of variables that defy my ability to apply sensible objective logic to the claims alluded to with HGAL references.
My own feeling is this; while a stone with a certain hardness and apparent fine-ness is sought/needed to hone successfully, to be truly happy with the outcome of my efforts on any stone, I have to be able to maximize the potential of the stone. Simply put - a 5+/3+/3+/3+ stone isn't neccessarily going to give me a better result if I'm not in-sync with it. I have a brilliantly fine and insanely hard Nakayama that defies my ability to finsih on with just water. My touch and technique are challenged to the limits of my patience each and every time I use it. Most of the time I blow it and I wind up degrading the edge a bit. This is not an issue really, it's more of a challenge. I enjoy the challenge but I only try to finish on that stone when I am really feeling that I'm on top of my game.
At the same time, I have another stone, an Okudo, that is obviously softer and less fine than that Nakayama; and yet I can do no wrong with it. When I do nail an edge on the Nakayama, the results are mind-boggling. But then, so are the results off the Okudo. I would say the egdes are different, rather than say that one is 'better' than the other.

About lapping -
I only use a DMT to lap a Jnat in the early stages. Once the top is leveled off, I continue lapping on w/d paper up to 2k, and then I turn to a a well broken-in BBW for a near-final polishing. After that - I have a few good sized Tomo Nagura to finish up with. On some stones, with each new honing session, I can usually see the top becoming even more polished. I have used a 1.2k DMT to raise slurry, and it worked fine. I was going to get an 8k DMT to experiment with, but since I'm really most comfortable using a Tomo Nagura I decided to stick to working that way, at least for now.

As far as JNat lapping I've had great success with the following progression:

200 grit sandpaper
400 grit sandpaper
Well worn DMT 325
Well worn DMT 600
1000 grit sandpaper
BBW ( from my Le Dressante au Bleu )
Coticule ( other side of the above mentioned Coticule)

I've lapped my Yaginoshima Namazu, Ozuku Asagi and Ozuku Mizo Asagi in this fashion.

Sharpman
Here is another group of photos that describes how the polishing went along in stages. I am using that same Sheffield blade these next 2 weeks with the edge in the photo #449. A simple edge that I tailored to my tastes with 20 or so strokes in a tomonagura slurry. Pretty basic stuff. Hope this helps somehow, Alx

For kannasama and the rest of you smart folks out there.

Why do people end with sharpening on a stone with only clear water, no slurry? It seems to me that as you’re refining the edge on slurry, the slurry keeps breaking down into smaller grits. Let’s pretend the stone is 7K. When you work the slurry it breaks down to 14K (as I said, let’s just pretend). That’s pretty fine, and certainly a finer grit than the stone. So why rinse the stone and return basically to a coarser grit, the original 7K original grit, to finish off? It seems to me that that would negate using the slurry, and take away the fine finish you achieved using the slurry.

I know I'm obviously missing something here, so maybe someone could enlighten me? I have, among other stones, a Japanese Natural Blue Mountain stone (about 2-3K, I believe), and a #4 Awase Toishi (fine finish stone about 6-7K, I believe) that I use as part of my progression. I finish my progression on a King 8000. Right now I don’t have anything finer than that. I would like to know about slurry and using the #4 Awase Toishi as a final finish stone by just finishing with no slurry, only clear water, if that would be possible. That’s why I asked the question above.

Any help or clarification would be greatly appreciated.

Thanks,

bruseth

Well looking at the pictures, that doesnt show to me that the nakayama provides a 30k edge, and the facts that 150 strokes were made on the 30k shapton are inconceivable. Nevertheless, in the past i was intrigue in the shapton 30k and i was reading on here, and other forums that most
use just a few strokes on the 30k or if more the edge collapsed or overhoned.Foremost i dont doubt the nakayama ability to give a great edge for sure,but why the resemblance or comparison to a factory finishing hone that in all probability will yield the same results religiously.