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Does this HARDNESS SCALE look silly, or can you make suggestons.

I have always struggled with the 1-5++++ hardness scale for razors but have used a 1-10 scale for tool size stones, but in either case the stones for razors in the 1-5 scale have always fallen into the 4+, 5-, 5, 5+ and or course the famous 5+++ ranges. So what is the point of having the numbers 1,2,3 of the scale. I noticed that Takeshi of AFramesTokyo uses the 1-10 scale. Here is my take on the 1-10 scale. Any suggestions would be appreciated, comments and criticisms too.

Alex


Chart
#1 to #2: Soft Aichi/Mikawa or Odori nagura can be 1-2. The softest old mined iro-mono-toishi (literally "colored-things-stones") and light pastel or white early mined stones you can dent with your fingernail can be #1 to #2 in hardness. These soft stones if you can find them, can be used without a tomonagura and will self slurry and they soak up water very quickly even as you are looking at it.

#3 to #5: Medium soft kiita, harder nagura, softer iromono like yellow, red, orange can be 3+ to 5 hardness and cannot be dented with a fingernail. The softest green asagi can be in the 4 to 5 hardness range but these more intense green asagi are not common and they will self slurry under steel sharpening. Water is absorbed easily and you can see it soaking in while you are looking at it.

#6 to #7: Stones like the majority of the duller green asagi, the harder iromono, rich deep gray to black gousa stones can be 6 to 7 hardness. The greatest majority of average tool and knife stones fall into this hardness range. Water is slowly absorbed and a bead of water can stand on the stones in high profile for 5 minutes.

#8 to #9: Stones that are to the touch with a blade are obviously hard and repel water like the hardest asagi, dark gray gousa, many light gray tomae, majority of suita and most mizu-tomae (mizu means water-thus blue). These stones do not self-slurry and do not soak up water easily or quickly and beads of water can stand proudly for up to 20 minutes.

#10: Very hard stones to the hardest, like super hard tomae, super hard suita, dark heavy-dense gray tomae. These types of stones will not volunteer any slurry and even when a diamond plate is used to raise a slurry it is slow and takes noticably more passes to raise what is almost always a white slurry. Level #10 stones are commonly used as a platform base stone for a nagura progression. These level 10 stones do not absorb water easily and a bead of water can remain with a proud profile for an hour or more if left on the stones surface.
 
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Makes sense to me. And if you use one decimal point as Takeshi does you can refine even more. I have not in the time I have been watching seen anything on AFrames beyond 9.2
 

Steve56

Ask me about shaving naked!
Alex,

We as buyers of stones have to get used to what the sellers use regardless of the scale. I've bought a number of stones from Takeshi, and it would be a mistake I think, to assume that 10 point scale is linear or is for razors only. He describes finishers for example, as being in the 8-10 range, but IMO, an 8.8 from him barely qualifies as a razor finisher (though it would no doubt be a great knife finisher), and the finest stone he's ever listed that I've seen has been 9.4 or 9.5, and I have a 9.4 from him. It's indistinguishable in fineness from the kiita I bought from you a few weeks ago.

So as far as razors go his fineness scale would be IMO, from 9.0 to 9.5, a 5-step scale from the threshold to the finest.

I have to say, I think all the stone sellers I'm familiar with do a good job of describing their stones, though the scales are different. Takeshi does not distinguish knife finishers from razor finishers except categorically by type ie all suitas are knife/tool finishers, all tomae seem to be razor finishers. Max has categories for knives, tools, and razors.

I think the "++++" is just an advertizing technique to appeal to those who want the very hardest stones, equating that hardness with fineness, which is in general probably true, but those extra plusses come with a lot of baggage like needing a diamond plate to slurry, scratchiness, slow cutting, etc.

Personally I'm at the point where I don't want or need those hard stones, I'm looking for the small percentage of stones that are both very fine, produce smooth razor edges (in a razor hone of course), and are well behaved.

Cheers, Steve
 
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Great points all around and interesting descriptors of stones. I typically describe stones in a 1 to 5 scale with a 5+ being stupid hard. I only have one or two stones I'd call a 5+ and they are for absolute final finishing only; I don't even waste time using a full nagura progression on them any more as I have other base stones that play with nagura stones better.

I think when vendors attach all the "++++" to stones they're just letting people know that these are insanely hard stones and want to make that fact very understandable to the consumer. Using those insanely hard stones does seem to be more difficult; as Steve mentioned they can be scratchy and slow and usually get tamed, in my house, with a softer tomo as I don't really like the finish imparted by diamond plate slurry on knives or razors. FWIW my go to 'nagura' on these stones is typically something like uchigumori as I find it fine enough to finish on but very easy to raise a slurry with, seems to do the trick.

One of the big differences I have noticed and discussed with friends is the aggressiveness of some stones. Some suitas and even the very hard tomae stones are so hard/aggressive that they, for lack of a better term' smudge the softer steel that clad core steel in knives and tools. Jon Klip seems to think there might be a correlation between the level of impurity in the cladding and how easily this smudging effect takes place.

At the end of the day different users will be able to impart different edges using stones that are similar to other people. For example, finishing under running water on a softer stone can leave an edge just as keen/polished as finishing on tomo slurry on an ultra hard base stone depending on the users techniques. Some people like edges on their knives from softer stones; grabbier and toothy as compared to slick and laser sharp OR on razors where softer stones can leave more coticule like edges.

I like how Takeshi rates his stones and how he is very detailed in his descriptions. If an ultra hard stone is smooth on water only and not sticky he is damn sure to write that down so the user knows what he is getting. He is also very good at describing the brightness/polish level a stone can impart but I wish he'd photograph his results. Maksim does attempt to do this but I don't think his pictures truly capture the edge/polish/contrast well. As long as the vendor is consistent with his descriptions I think whatever rating system he/she decides to use is just fine.
 
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I like Takeshis ratings as well. And I agree with Brooksie about the stupid hard stones. Seems that the best practical finishers I have are not the hardest. How bout rating the stones as razor and knife stones? Pictures of base stone slurry after 10 strokes and then 30 strokes will reveal much. And whether it needs a tomo nagura or not regarding scratchiness is good to know as well.
 
Hey Alex - is this for your own personal understanding, or is this scale something you plan on using on your retail website?
 
I'll agree something needs to be done. I've seen a few 3 rated stones and I just assume it must be a clump of dirt or something, because many of the 5+, or Very hard, etc stone's I've been sold turned out to be softer than my softest Thuri's, which I consider extremely soft.

I'd actually love if there were some sort of specific gravity calculation done to give me a definitive measure of a stones density; sure it's not equal to a value for hardness, but it's related closely enough, and you can't put a value on having something objectively measured that can't be colored by what someone WANTS a stone to be. I'd be happy to settle for a water displacement/dry mass measure on Jnats.

I really think the inaccuracy of the hardness gradings survives for a very different reason than the inaccuracy of the grit rating (which survives because of claims that grit depends on slurry breakdown, so it's user error if your stone is coarser than you wanted) but rather because hardness both is in a realm where inexperienced users will accept the claims as fact because they have few if any points of reference, and rocks are hard, if you don't have a harder stone to compare against, a pretty soft jnat will seem quite hard.

Bear in mind that I don't believe I've bought more than three stones from the same vendor, and I tend to enjoy gambling on vendors who are new or of unknown reputation. But if I were looking at buying a stone, not as a gamble, but as a single purchase for a lifetime of use, I'd consider an objective measure of the stones density invaluable.
 
Is something like a Mohs hardness scale reasonable? Not THAT scale of course but similar? You'd probably only need 6-9 of the Mohs scale, but it's empirical.
 
Hardness is actually the last thing I'm concerned with. Id sooner know the speed and fineness. But there seems to be a trend of hardness being the most important thing.

All I want to know is that the stone is hard enough.
 
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Hardness is actually the last thing I'm concerned with. Id sooner know the speed and fineness. But there seems to be a trend of hardness being the most important thing.

All I want to know is that the stone is hard enough.
So your scale looks like "Yes, Ferrari, Beyonce"? :w00t:
 
Hey Alex - is this for your own personal understanding, or is this scale something you plan on using on your retail website?
Keith
It would be for both. At my end I just have a hard time with the plus and minus thing and the numericals are just too crowded in the 4s & 5s on my site that it makes my head spin. Not that it still won't be still spinning but hopefully a bit slower. If I am not mistaken it was 330Mate that cooked up the 1-5 scale where as So-san at Japan-Tool would just not use a scale and say that what is hard for one person would not be exactly the same for another's*.

*I had to fiddle with that sentence a bit so as not to offend anyone.

So your scale looks like "Yes, Ferrari, Beyonce"? :w00t:

Very funny Lee you silly boy.

The suggestions are greatly appreciated.

Alex
 
This is a good discussion to have.

I'm reminded of something one of my professors said that, once I was responsible for grading papers, proved to be inarguably true. This was one of the smartest people I've known and he said, regarding exam essays, the following:

"I can easily tell what paper is an A and which ones are an F. The ones that are neither are C's. I can't tell, however, the difference between a B and A or a B and a C. Same with D's. I have to give them out because that's the nature of the job, but on any given day, I could just as easily give one as I could the other."

I've found this general principle of knowledge to be incredibly helpful in lots of other areas. As a result, the numbers I've seen assigned to stones for their "hardness" and "fineness" I largely ignore. Seriously, do you think you could reliably tell the difference between a 9.2 and a 9.4 fineness Jnat? I couldn't. I don't actually believe anybody can without a battery of sophisticated laboratory equipment.

All I want to know is whether it's a hone suitable for razors or not. I may want to know if it's soft, hard or really hard, but that's all I think I can rely on from a seller. Numbering systems satisfy our need for certainty, but when the are incapable of accuracy, then they do more to mislead and create confusion than they do to clarify. As long as a seller guarantees my satisfaction with the stone, within limits of course, then I'm willing, happy in fact, to carry some of the burden of figuring it out.
 
This is a good discussion to have.

I'm reminded of something one of my professors said that, once I was responsible for grading papers, proved to be inarguably true. This was one of the smartest people I've known and he said, regarding exam essays, the following:

"I can easily tell what paper is an A and which ones are an F. The ones that are neither are C's. I can't tell, however, the difference between a B and A or a B and a C. Same with D's. I have to give them out because that's the nature of the job, but on any given day, I could just as easily give one as I could the other."

I've found this general principle of knowledge to be incredibly helpful in lots of other areas. As a result, the numbers I've seen assigned to stones for their "hardness" and "fineness" I largely ignore. Seriously, do you think you could reliably tell the difference between a 9.2 and a 9.4 fineness Jnat? I couldn't. I don't actually believe anybody can without a battery of sophisticated laboratory equipment.

All I want to know is whether it's a hone suitable for razors or not. I may want to know if it's soft, hard or really hard, but that's all I think I can rely on from a seller. Numbering systems satisfy our need for certainty, but when the are incapable of accuracy, then they do more to mislead and create confusion than they do to clarify. As long as a seller guarantees my satisfaction with the stone, within limits of course, then I'm willing, happy in fact, to carry some of the burden of figuring it out.

Mark

Good points. The decimal does add some burden if 80% of the stones you are judging are in the #9 & #10 range (Takeshi) or the #4-#5+++ in the smaller scale that almost everyone else uses. I am looking for larger targets with some delineaton with definition and figure if I have 7 or 8 numbers (numbers #3 thru #10) to aim at, for those 80% of stones, it might be easier at my end at least. I know what the A grade #10 hardness stones feel like, and the #3 grade soft stones are pretty easy being just above Mikawa nagura, the middle point is between #6 & #7. Maybe the middle is too soft and that is where some mistakes or judgement comes into play. What do you think?
 
Mark

Good points. The decimal does add some burden if 80% of the stones you are judging are in the #9 & #10 range (Takeshi) or the #4-#5+++ in the smaller scale that almost everyone else uses. I am looking for larger targets with some delineaton with definition and figure if I have 7 or 8 numbers (numbers #3 thru #10) to aim at, for those 80% of stones, it might be easier at my end at least. I know what the A grade #10 hardness stones feel like, and the #3 grade soft stones are pretty easy being just above Mikawa nagura, the middle point is between #6 & #7. Maybe the middle is too soft and that is where some mistakes or judgement comes into play. What do you think?

I think there are too many variables between the rock, the steel and the honer to make a distinction more precise than: this is not a razor hone; this is a razor hone; this is a very hard/fine razor hone. Because we deal with these rocks all the time, perhaps we forget how much useful knowledge has already been conveyed by just that much information. For 95% of your buyers, this should be sufficient. The other 5% may be able to tell the difference, but let's be honest, they're going to determine the nature of each rock on their own anyway.

I liken this to the wine business of which I was a part decades ago. Very few mammals can tell the difference between a 10 dollar bottle and a 30 dollar bottle of wine made from the same varietal. Most can't even tell the difference between the varietals. I've participated in literally hundreds of wine tastings and seen this over and over again. It doesn't matter, however, how many times this is proven nor how decisively this is proven. Two legged mammals still insist on meaningless 100 point scales for judging how good a wine tastes. I've accepted that it's part of the pleasure of the hobby and there's as much pleasure, more really, for a wine collector to talk about his "99 points from Parker" wine than there is in his drinking it. Over the years, I've decided that there's bad wine, good wine and very, very, very good wine. It's easy to avoid the bad stuff, and I don't feel like paying for the very, very good stuff (a rule I break, btw, for scotch). So, I happily settle for just drinking good wine and occasionally stumble upon something very, very good that got mislabeled or mispriced.

From an ontological perspective, a rating scale of 10 points is nonsense, but from a marketing perspective, it probably works very well. Nobody going's to buy anything below a 7, however, so you're pretty much back to 3 or 4 points anyway.

I guess what would work for me is throwing away a number scale altogether. It's ridiculous. Substitute for numbers, a lengthy description of the stone. What it feels like, how it hones; is it fast? is it slow? Is it ridiculously hard or buttery soft? Easy to hold? Susceptible to fracturing? Flexible enough to finish and be a pre-polisher for an even finer Jnat? The stones I like usually have an ineffable quality of just feeling good to hone on. I have a new arkie like that. It just feels right and the edges, so far, that it's turning out are really special. There's no number that describes this and words only get halfway there. I'll settle for the words.


My lawyer advises me to state that this advise is meant for entertainment purposes only. Any commercial application of this advice is not recommended. Side effects of this advice include diminished sales, irritated customers, overstocked hones and, in rare cases, rectal bleeding. If certain rare symptoms of this advice don't "abate" after 4 hours, see a doctor immediately. Or an exceedingly close friend.
 
Mark

Good points. The decimal does add some burden if 80% of the stones you are judging are in the #9 & #10 range (Takeshi) or the #4-#5+++ in the smaller scale that almost everyone else uses. I am looking for larger targets with some delineaton with definition and figure if I have 7 or 8 numbers (numbers #3 thru #10) to aim at, for those 80% of stones, it might be easier at my end at least. I know what the A grade #10 hardness stones feel like, and the #3 grade soft stones are pretty easy being just above Mikawa nagura, the middle point is between #6 & #7. Maybe the middle is too soft and that is where some mistakes or judgement comes into play. What do you think?

Takeshi grades his stones by the finish imparted on knives/tools that have a kasumi finish and determines his numbers by how bright/deep/shiny the core and cladding are. It's much easier to see the difference on large/wide bevels and easier to tell the difference between a 9.0 and 9.4 for example.
 
I liken this to the wine business of which I was a part decades ago. Very few mammals can tell the difference between a 10 dollar bottle and a 30 dollar bottle of wine made from the same varietal.
The difference there is I'm not sure I want to be able to tell the difference in wine, but I definitely want to know the difference in stones. :thumbup1:
 

Steve56

Ask me about shaving naked!
Ian,

I've actually done specific gravity measurements on a number of stones soft to hard, and the spread is too narrow to be of use, we're talking 2.6g/cc plus-minus at most a couple tents, and most are within plus-minus one tenth. I don't think the density will tell us what we want to know.

I've concluded about what Mark said, there are too many variables to be able to make a couple of measurements and know all, and I'm a physicist by education and an engineer by profession.

And Brooksie points out something Takesi does in his descriptions that is very useful, when a hard stone can finish on clear water, without slurry he says so and that means something. Usually that's a vintage stone or one that's a very high quality. Alex also does the same thing, telling us when a clear water finish can bump the edge up a bit, but I don't think Takeshi and Alex are using the description in quite the same way.

Oddly enough, I've seen common adjectives describing stones used by Takeshi and the Greek guy that sells on eBay, only for Hatanaka Hatahoshi stamped stones. That makes me think Hatanaka in some cases supplies the English description for the Hatahoshi stones. That inspired me to make a post a while back asking if the "model" of stone, like "Hatahoshi" meant something specific but no one knew. BTW, you can still buy Hatahoshis from Hatanaka, he has them listed on the Japanese website last time I checked.

Cheers, Steve
 
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