Thread: Natural Stone Grit Confusion

Originally Posted by northpaw

Out of curiosity, how much work can a relatively experienced user do in that time? Say you had a pile of razors and wanted to take one good-looking picture of the edge of each - how many could you do?

You can do as many as you can fit on the holder. The chamber of the one we have can fit 2x 1" wide microscope slides.

Let me say first that I tend to be pompous and long winded, so beware. Those of you who have read some of my other articles know this, and I apologize if I tend to repeat myself. Although I shave with a straight my years spent on stones has been mainly in regards to carpenters blades.

Japanese stones have been used for so long without any numerical number system attached to them partly because they come from a country that lived and existed in a way that, at least in the past, tended to favor words over numbers while describing objects that occurred in nature.

The words arato or shiange tended to be sufficient enough to describe stones that in the in the hands of simple workmen would perform a simple task.
　
In Japan it is usually understood that you should test a stones ability before you buy it, and that is still a good idea. But because I brought these stones to the U.S., and set up a website, I felt the need to provide some numerical system to use as a tool for description so that maybe a long distance conversation could begin based on common ground. I chose the Shapton 30k on glass stone as the finest “commonly held grit” in the market place as a marker of sorts. I bought my 30k stone from Harrelson Stanley, and borrowed a few other Shaptons from a friend and began photographing the scratch pattern left on Japanese laminated blades as a build up or a library of scratches for comparisons alongside the natural tennen toishi scratch patterns.

In all honesty, I was very nervous at first about publishing these early photos of the grit patterns from Shapton stones because the scratches did not change very much and there was a lack of delineation between the 15k to the 30k stones. I spent hours and hours and many cut fingers trying to get photos that would define a sharper more defined step between these two stones. One time I made 500 laps on the 30k stone to try to get a finer polish and in the end all I got was a burnished blade surface, it did not sharpen the blade any further.

The proceedure for the photos of all the scratches left by both natural and synthetic stones were, with a freshly lapped stone but with no slurry and were the result of between 25 to 50 forward edge into the stone passes at right angles to the cutting edge. No drawing the blade back in contact with the stone. I first lapped the stones with a diamond Atoma plate to open up virgin grit, washed the surface with fresh water and then sharpened on that surface with no slurry. To get beyond previous scratches from previous stones I side sharpened the blades edges first so that optically there would be no 90 degree to the blades edge scratches visible. All the photos were taken with the light coming from a single source to the left and at 90 degrees to the scratches. This is a raking light meant to highlight the peaks and valleys of the scratch pattern. In this way any scratches running parallel or greater then 45 degrees in line with the light source are not visible because the light fills up the valleys.

There will always be scratches in steel left behind from an abrasive action. If you see lower magnification photos, like I take, of a surface without scratches it is because it’s either a highly burnished surface or because the scratch valleys are filled with light when the photo was taken. After all sharpening is just the removal of steel, and a shaper blade is just that same task done with finer grit abrasives than those used before. The caveat being low magnifications, of course with higher magnifications scratches will eventually appear in the photos although possibly ill defined.

I had waited a couple of years, watching all of the forums hoping that someone else, more scientific then myself would stick their neck out and say, my tennen toishi is 15,000 grit, and this is why. Or this one is 24,000 because I measured it and this is how it was measured. No one would venture beyond “it is hard”, “it is fine”, “it is the finest I have ever tried”. So-san even when so far to skirt the question completely by only by passing on that “my father never talks in those terms” and suggesting that no one else is Japan does either.
　
　
Think of it, why would Shapton or Norton take the time and cost to measure the grit particles of a natural stone? They do it with their own stones, they grade them by microns and ascribe numbers. It appears that the mystery surrounding the grading of natural stones seemed better left not said by those with the resources to demonstrate such facts. The miners who by risking dangerous conditions extract these muddy gems are too busy to bother and in any case the domestic market is not demanding it of them.

The system I used to photograph the scratch pattern for my website can be copied for about $50, and you end up with a great camera to use for other things. This system using a Bushnell Portascope and a Olympus camera was designed so that others worldwide could copy it by buying the items on E-bay, and I hoped it would create some common ground for a conversation to begin. Now granted there are better ways to take photos, sharper lenses, higher magnification, more consistent comparison grit particle medium, etc. but my system has only 3 components, the light, Portascope and the camera. But believe me I have been waiting for someone with access to a university lab to really get into it.

I have also found however that you can magnify a scratch pattern too closely, sort of loosing the trees for the forest syndrome.

There is another quality that is important to the sharpener that is a little more difficult to quantify, and that is the use ability of the stone, how well does the stone perform. We describe this when using synthetic stones; the stone cuts fast, or it loads too fast with swarf, it is soft and dishes quickly, etc. We ask, how good is a stone that glazes every few strokes? There are a lot of factors in how we choose stones. In synthetics we tend towards brands that feel good with some steels, shun others that don’t or even go to the expense to match up stones for particular steels we keep in our quivers.

In many ways the language we have and use is too crude for the job of describing the complicated yet subtle task of sharpening with natural stones. Ascribing numbers will not do this completely, they may help some but really in the end it does come back to testing out the stones first. Like they say, the proof is in the pudding. Alx

Originally Posted by Lesslemming

well SEM pictures are probably not the most cost effective way to investigate an edge as a set of SEM photos can cost up to 10.000 Bucks, I guess.

I would go with the "feel". I have my ways to test an edge, not a stone.
The TPT in the high grit range is quite effective as well as the HHT and of course the shave.

A fast cutter isn´t of course always a lower grit hone.
The higher the content of abrasives, the faster it cuts.
I came to the conclusion that most j-nats are very, very fast cutters for their grit range and have high amounts of abrasives.
A slurry on a j-nat always makes it cut really, really fast.
Of course the results change, these stones tend to produce a hazy finish (kasumi) when slurried,
even though they polish when used without slurry.
And most of the time the stone used in polishing mode without slurry
will not be strong enough to polish out the hazy finish left by his own slurry.
Interesting, me thinks

In my limited experience, this is my experience also. I was amazed how fast my Nakayama cuts in it's own slurry. When i bought it, I was kind of looking for a finisher to compete with my Shapton 30k. What I got was an educational experience, as i was amazed how fast the Nakayama cut in the prefinishing stages. I was also impressed with the geometry of the bevel and lack of micro chips as the blade skews across the silky surface of the Nakayama. Also the lack of swarf loading and sticking to the surface with or without slurry compared to synthetcs. Something tells me if you knew you stuff and your stone(I am nowhere near knowing my stuff with these stones) your Nakayama could in effect be a one stone show taking you easily from rough bevel set to finish.
This effective cutting range is my main point of confusion. Is it normal that most Japanese Stones perform this way? If so, where do grit estimates come from? In other words, those of us that want simple answers to quantify one of these gems might be left scratcing their heads as they really don't behave and work quite the same way other stones do. Seems like a huge learning curve to me and quite the challenge.
M

Originally Posted by OLD_SCHOOL

I have met many experienced Japanese people who use and sell Japanese natural hones, including a person who's family spent generations mining from Mt Shoubudani, and none of them will even attempt a guess at grit range. All you will be told about a natural hone is that it's either coarse, medium, or fine. They all hone by feel, not by numbers.

Something else worth keeping in mind, no two (Japanese) natural hones are alike,you can have two hones mined from right beside each other, and one could be as hard as diamonds, and say the 50k range for grit, whilst the other is as soft as warm butter, with a 1k grit range.

If your going to try find the grit range of your natural hone, you are better to conduct the tests yourself, and remember that the results of those tests are relevant only to that tested hone. This will be the most reliable and accurate method.

For this reason, SRP members are fortunate to have their very own guide to help them into this world of Japanese stones and help them get their feet wet. For all my education which I paid dearly for(literally) some of the best educators do their services in the most unlikely places.
Also want to thank Alex for trying to clear up and his personal efforts to help others wade in these confusing but most rewarding waters.
Mike

In my opinion, and somehow I like to believe that a lot of the ancient Japanese masters in sharpening would agree with me, he who asks the grit rate of a natural honing stone does not really understand the nature of these hones.

I am aware that statement may sound offensive to some of you, but it's my honest and respectful opinion.

Man made hones are made from industrially produced particles. There are a number of technological solutions to separate particles according to size. Hence the manufacturers truly have an idea what particles size their hones are formulated with. I guess that at first, the grit rating correlated to the actual particle size. I also guess that more recently, marketing departments have a saying in it as well, and that hones are often graded in comparison with what the competition offers. A bit like Intel and AMD rate the clock speed of their CPUs...

But at the end of the day, the size of the honing particles is only one contributing factor to the final edge quaility. How deep a particle penetrates into the steel is far more important. That is correlated to its size, but also to: the hardness, the actual shape of the particles, even the pressure applied by the honer, how densely packed they are in the hone, the properties of the binder, how easily the particles wear (consider the vast difference between a new DMT-E and one that's been well used), whether the particles are friable or not. I may have forgotten a few parameters.
For that reason, even the numbers of synthetic hones make only sense in ordering the hones of one manufacturer. They might as well have designated the Shapton series as 1, 2, 3, 4, and 5, instead of 1000, 2000, 4000, 8000 and 16000. Where the numbers of another manufacturer fit in, is something that can only be figured out empirically.

Enter natural hones. If we would turn a sample into slurry and rely on scientific methods for separating the particles and measure them, I'm pretty sure that we would be surprised to find: A. that they show a wide range in one and the same sample. and B. the median size would be much larger than the quality of the edges suggest.
Those who regularly inspect scratches with a microscope already know that. But all the other parameters I summed above, might be more favorable, compared to a synthetic competitor, or perhaps the fact that it's a natural product might add some extra appeal.

I have often compared honing to playing a musical instrument. Talk to saxophone players, and they each have their personal preferences about different brands and makes of reeds (there are Internet forums expanding continuously about that topic ). Most players even customize their reeds and also the tool used for that is subject to personal preference. Inexperienced saxophone players always blame their material for producing a poor sonority. Seasoned players know that it's all a matter of technique. Preferences say more about the person than about the product. I believe the same is true for fine whetstones.
A seasoned honer thinkers far less about the perfect tool, the highest grit, the best feedback. He is past all that, and knows it are his hands and focused mind that produces the fine razor's edges. And yes, he knows his tools, but that knowledge can sadly enough not be expressed by a number.

Kind regards,
Bart.

Well said Bart! I have to agree that attributing a number value to a natural stone is kinda silly, but I can KINDA understand why people ask that question. For me, the only reason I would ask would be to just have a rough idea as to how the stone cuts compared to what you get on synthetic hones.

For people wanting to replace synthetic hones, without trying them, all they have is the number to figure out which stone could replace, for example, a Norton 4k. That's the only reason I could see for compare it to a synthetic grit hone.

Originally Posted by Bart

In my opinion, and somehow I like to believe that a lot of the ancient Japanese masters in sharpening would agree with me, he who asks the grit rate of a natural honing stone does not really understand the nature of these hones.

I am aware that statement may sound offensive to some of you, but it's my honest and respectful opinion.

Man made hones are made from industrially produced particles. There are a number of technological solutions to separate particles according to size. Hence the manufacturers truly have an idea what particles size their hones are formulated with. I guess that at first, the grit rating correlated to the actual particle size. I also guess that more recently, marketing departments have a saying in it as well, and that hones are often graded in comparison with what the competition offers. A bit like Intel and AMD rate the clock speed of their CPUs...

But at the end of the day, the size of the honing particles is only one contributing factor to the final edge quaility. How deep a particle penetrates into the steel is far more important. That is correlated to its size, but also to: the hardness, the actual shape of the particles, even the pressure applied by the honer, how densely packed they are in the hone, the properties of the binder, how easily the particles wear (consider the vast difference between a new DMT-E and one that's been well used), whether the particles are friable or not. I may have forgotten a few parameters.
For that reason, even the numbers of synthetic hones make only sense in ordering the hones of one manufacturer. They might as well have designated the Shapton series as 1, 2, 3, 4, and 5, instead of 1000, 2000, 4000, 8000 and 16000. Where the numbers of another manufacturer fit in, is something that can only be figured out empirically.

Enter natural hones. If we would turn a sample into slurry and rely on scientific methods for separating the particles and measure them, I'm pretty sure that we would be surprised to find: A. that they show a wide range in one and the same sample. and B. the median size would be much larger than the quality of the edges suggest.
Those who regularly inspect scratches with a microscope already know that. But all the other parameters I summed above, might be more favorable, compared to a synthetic competitor, or perhaps the fact that it's a natural product might add some extra appeal.

I have often compared honing to playing a musical instrument. Talk to saxophone players, and they each have their personal preferences about different brands and makes of reeds (there are Internet forums expanding continuously about that topic ). Most players even customize their reeds and also the tool used for that is subject to personal preference. Inexperienced saxophone players always blame their material for producing a poor sonority. Seasoned players know that it's all a matter of technique. Preferences say more about the person than about the product. I believe the same is true for fine whetstones.
A seasoned honer thinkers far less about the perfect tool, the highest grit, the best feedback. He is past all that, and knows it are his hands and focused mind that produces the fine razor's edges. And yes, he knows his tools, but that knowledge can sadly enough not be expressed by a number.

Kind regards,
Bart.

Originally Posted by OLD_SCHOOL

Yes, a high quality Nakayama hone can be used from bevel setting all the way to final polish, but it can be a slow process.

I am very greatful to have aquired from you a hard stone that is indeed a fast cutter. Slurry changes color very fast and it turns out to be the quickest stone in such a wide scope of "effective cutting" range.
There is such precious little information available on these stones available to Westerners. Again, I thank(for sure there are many here who feel the same) the natural stone gurus for helping to understand and gain a sharpening experience that is "Ne Plus Ultra". I would be first in line to buy a book on the subject if you feel so inclined.
Mike

1 hour on the SEM @ my University is 160 bucks.

Wow, really? Well then I misjudged very hard ^^
Maybe there could be an arrangement for a finisher- comparson on SEM.

Send 10 different finishers with 10 equal razors to a honemeister
and the 160$ could be founded by members of this forum

A blast from the past .... here are photos taken by Tim Zowada of various hones and the edges of various razors sharpened on those hones.

Here is a web article on taking magnified photos of edges with an OX3 microscope. I'm not knowledgeable on this topic but found this through a google search. Thought it might be of interest to some folks.

Originally Posted by JimmyHAD

Here is a web article on taking magnified photos of edges with an OX3 microscope. I'm not knowledgeable on this topic but found this through a google search. Thought it might be of interest to some folks.

That's an amazing resource about sharpening, Jimmy. Thanks for sharing.