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What makes natural stones such good finishers?

I’m always surprised when I find natural materials that outperform anything that man is able to produce. It happens quite often and seems to also be the case with natural finishers. Most people that have been straight razor shaving for long enough tend to agree that a natural finishers are unrivalled for face feel and performance. How can it be that random natural deposits so consistently outperform all of our man made efforts to improve them?

At first glance, synthetics seem to have a big advantage. We can closely control all aspects of their construction. The partical size, shape, hardness and size distribution can all be precisely engineered. So can the properties of the binder. Under lab conditions all impurities can be removed from the mix. There is no obvious reason why a perfect finisher could not be produced in the factory.

There’s no doubt that synthetics work. They can cut fast and perform in a very predictable manner. They can cut very finely and produce amazingly sharp edges. For the early sharpening stages they run rings around naturals.

Where the synths fall down is in the ‘feel’ of an edge. Not important for knives or tools but of the outmost importance to razors. Why has it not been possible to produce a synthetic that gives the smoothness of a Jnat, Ark or Thüringian edge?
 
My thoughts on this are that it has most to do with the surface finish on the bevel. This finish also extends to and affects the edge.

I do not believe that a natural stone finish will produce a "sharper" edge than a 0.1μm diamond pasted balsa strop. A natural stone finish may however produce a more comfortable feeling shaving edge. This may be attributed to the bevel surface finish and how that reacts with the skin interface in the presence of water/lather.

I have not tried a lot of different natural stone finishers, just three and none of them had famous names. My preference has remained for 0.1μm finishes. With suitable short X strokes at the end of finishing, I get edges that I am extremely happy to shave with.

Why can't science/technology now produce the equivalent of good natural stone finishers? It could be that naturals are not uniform in their grit particles. Manufacturers of good synthetic whetstones work hard to ensure that their grit particles are uniform throughout.
 
It might have to do with the types of abrasive particles in natural stones.

Synthetics are often things like silicon carbide or aluminium oxide, which are fast cutting and cheap to produce.

Natural stones are things like quartz, or garnets, or what have you.
 
It’s pretty simple: no producer optimizes their manufacturing processes for straight razor honing…

All the science, R&D, and money spent on innovation have different goals in mind. Typically edge sharpness, uniformity, consistency and ease of use
 
Now this is an interesting question!

And there are probably a lot of answers, but I think one could probably summarize it by saying: heterogeneity. There's an awful lot more going on in a natural stone. And to try to reproduce that in a synthetic stone would be crazy, and expensive. It's also I think why natural stones are more versatile. If you look at something like the JNS Synthetic Red Aoto they specifically try to replicate it by mixing 2k and 4k grits, with a reasonable degree of success, but it's still not an Aoto.

Some factors that tie in are as David points out - abrasive. The large majority of natural whetstones are based on Silica, synthetic stones aren't. Silica / Quartz is only marginally harder than HT-ed steel (7 vs about 6 Mohs) and it rounds and dulls quite easily, before slowly - new material is exposed. You have a constant combination of how aggressive your abrasive particles are, which is much less marked in AlOx and SiC based stones.

You also have other kinds of silicates in natural stones; some harder than steel, some softer, some harder than soft steel, but not as hard as hard steel. I personally have a hunch that micas have a larger impact on a stone that one might think. Stones with particularly high mica contents tend to feel quite nice to use, and they polish very well.

There are all sorts of other things at play too obviously, but it's this kind of heterogenous plurality that I think makes the best natural stones very good. And for the same reason also the majority - not very good. You can sharpen steel on basically any rock you ever pick up, because quartz is everywhere. But it's probably not going to be the best whetstone in the world, because you need a kind of perfect storm; where the variables and attributes of the stone are all pulling together and playing to the same tune. Whereas synthetic stones eliminate and homogenize this risk.
 
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Two thoughts come to mind. The lesser thought is that superior products often do not come to market because they are remarkably expensive to produce.

The greater thought is to reflect on the sources of each type of stone. Man is imperfect and his designs are imperfect. God is perfect and his designs are perfect. Natural stones will always be superior to man's imitations.

There is an old joke that describes a scientist telling God that he is no longer needed because man has learned to create life. God says, "Show me". The scientist bends over to pick up some mud, and God says, "No, no, go get your own dirt. That's mine".
 
I’m always surprised when I find natural materials that outperform anything that man is able to produce. It happens quite often and seems to also be the case with natural finishers. Most people that have been straight razor shaving for long enough tend to agree that a natural finishers are unrivalled for face feel and performance. How can it be that random natural deposits so consistently outperform all of our man made efforts to improve them?

At first glance, synthetics seem to have a big advantage. We can closely control all aspects of their construction. The partical size, shape, hardness and size distribution can all be precisely engineered. So can the properties of the binder. Under lab conditions all impurities can be removed from the mix. There is no obvious reason why a perfect finisher could not be produced in the factory.

There’s no doubt that synthetics work. They can cut fast and perform in a very predictable manner. They can cut very finely and produce amazingly sharp edges. For the early sharpening stages they run rings around naturals.

Where the synths fall down is in the ‘feel’ of an edge. Not important for knives or tools but of the outmost importance to razors. Why has it not been possible to produce a synthetic that gives the smoothness of a Jnat, Ark or Thüringian edge?
Have you tried the Gok 20k? I found it to be pretty smooth.
I have never shaved off diamond paste so can't really judge.
 
I think that the better question over “what” is “who?” The answer…Mother Nature!

Vr

Matt
 
I will not dispute how great natural finishers can be, but I would like to ask those that spend a lot of time using natural finishers, when was the last time you finished a razor on your 12k synthetic. I ask because as I spent more time with my two JNATs, my honing improved, and now when I use my Naniwa 12k the edges feel very comfortable.
 

Steve56

Ask me about shaving naked!
Warning: a bit of rambling follows.

Synthetics - at least some of them - are certainly very capable of making excellent razor edges, including pastes. I can tell the difference between a good natural edge and a good synth edge, but if you’re just starting out, you might or might not tell much difference. And I could shave off a nice synth edge from now on and be OK with that. But the best of the naturals to me make a smoother feeling edge while shaving.

A few years back, I was talking with Takeshi Aoki, and he said a razor hone must have 4 attributes. Let’s look at them and compare them to synthetics.

1 It must be fine. If it isn’t fine enough, nothing else matters.
2 It must not have ‘toxic’ inclusions or features that can hurt a razor edge
3 It should have a narrow grit range, IOW no coarse grit mixed in with the fine
4 How the grit ‘lays on the stone surface’ (paraphrasing his words) is important

Numbers one and two are slam dunks for synthetics, this is what they excel at, being able to make any size grit in a pure matrix. The other two aren’t so simple.

The Japanese stones that I own almost all do not leave coarse scratches on the bevel. Shapton Pros are notorious for that, though I have never determined that the coarser scratches affected the final edge, though I was not finishing with them. The most common scenario for the formation of JNats is that a volcanic event discharged ‘stuff’ into the air, or maybe water, the dust drifted and fell out. Larger, heavier grit fell out quickly, finer grit traveled further from the ‘event’ before falling out. The dust eventually became stone. This kind of action produced a very narrow range of grit for any given stone, narrower than almost all synths (I haven’t tried them all, lol), even narrower than Shapton Glass. A good one is basically all one size grit. I think that it’s possible to have very narrow grit distributions in synthetics but they would become very expensive. The Shapton Glass have one of the best grit distributions (as evidenced by observing the bevel) but they are also comparatively expensive.

‘How the grit lays on the stone’ is an interesting statement. English is not Takeshi’s first language, and there are some different ways of looking at this unusual and thought provoking statement. One is the shape of the grit. JNats typically have layered clumps of grit, at least according to Todd Simpson (Science of Sharp), and maybe these layered clumps are not always oriented the same on the surface of a stone? The clays or matrix of a JNat may also affect how the grit interacts with steel, but that’s conjecture. It is certain though that some are hard, some soft, some smooth, some less so, some fast, and some slow.

Both Arkansas and vintage synthetic barber hones are not that fine, they produce the results of much finer grits when the tops of the grit particles become flattened with use and produce shallower scratches. Hard JNats behave similarly but to a lesser extent, acting finer as the surface becomes polished or burnished with use. So maybe this is an example of ‘how the grit lays on the stone’. This characteristic of Arks and barber hones is important because most modern synthetic whetstones are designed to release fresh, sharp grit during use, so this effect does not exist for most of them. Extremely hard synthetics like the Gokumyo 20k do seem to exhibit different performance based on surface finish, like an Ark or vintage barber hone.

Coticules are also not that fine, estimated at around 4-6k grit. The spherical garnets however, produce wide shallow scratches that overlap and produce an effect of a finer grit. So maybe the same thing happens by some mechanism in some JNats or other naturals? IDK.

Anyway, just some thoughts that might help explain why a good natural produces a different result than a good synth. I don’t believe that anyone really has a conclusive answer.
 
Well, there is a lot more available than 12k. Yes, you can shave very well off a 12k, especially with paste. Heck you can shave well off an 8k. But neither compare to a good natural finish, Ark (some other novaculites) or Jnat, for some slates and coticules, though I doubt most are finer than 8k comparatively, some maybe, but really no good way to make that subjective-less comparison.

The trouble is, if you want sharp, synthetics can get you there easily, and the more you hone the better those edges can get. But shaving is not about sharp, sharp is easy. A .50um stone, film or paste is just more sharpness. A 20-30k or .03um film will exfoliate skin painlessly, (weapers).

Keen and comfortable is the goal. Naturals can give you both, no synthetic can do sharp and comfortable. Paste can get you halfway there, making sharp tolerable, but not like a Natural.

Synthetics, stones, Diamond (stones and plates), film and paste deliver a super uniform stria and laser straight edge, because the grit is aggressive and uniform. High grit or hard bound naturals have random grit, some that is friable making a non-uniform pattern (sandblast finish) and a fine micro serrated edge that will cut hair and is easy on the skin, comfort. It is a combination of varied grit and grit size, binder and friability of the grit that deliver that unique edge.

So, could modern science do the same thing? Probably. But as said, we make up such a small market share and there is already a well-established contender on the market, there is no incentive.
 

Steve56

Ask me about shaving naked!
One other comment/observation on ‘how the grit lays on the stone’. I do knives too, and the current trend is hard, wear-resistant semi-stainless steel. Examples are SLD, ZDP, Cowry X, R2 and so on.

I have a 6” Yoshikane slicer made of SLD steel. I can put two JNats side by side, even down to the color, kiita usually cuts pretty well. Both stones cut carbon steel equally well and fast. But one will happily cut the SLD and the other will not, you might as well be rubbing the SLD slicer on plate glass.

What’s the difference? The grit is all silica.
 
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I think certain natural stones allow the user to achieve their best, and surpass it, more readily than synthetics. A synth is what it is, it can't be more or less. You can't turn a 12k into a 20k and while you can buy a 20k you can't turn it into a 40k. You go just so far as it's technology allows and that's it. Maybe you cheat it a bit with a lube, or running water - a marginal bump at best usually. Then there are the inherent issues with using Aluminum oxide as an abrasive, vs - say - anything natural. The technology is good, but it is 'limited' by its own design.
But, a Jnat, for example, is whatever it is to start but there is always more to give, rather - there is more to "get" if you work at it. I get much sharper and smoother edges off the Jnats I own now than I have ever seen off any man-made stones. Synthetic abrasive compounds, diamond, alundum, etc, in theory, can achieve greater sharpness, but that level of sharpness is irrelevant. Plus, due to particle type considerations, and their impact on the surface and sub-surface, They don't provide the edge-feel I am looking for.
Once the edge cuts flush and without hesitation, that's it - making the edge sharper does not give you the ability to cut 'flusher' or with less than zero hesitation. It's not a matter of grit or technical precision by a laboratory. The edge I want, is something created by imperfect means on imperfect things, all done imperfectly by an imperfect person - as perfectly as possible.
 
“I can put two JNats side by side, even down to the color, kiita usually cuts pretty well. Both stones cut carbon steel equally well and fast. But one will happily cut the SLD and the other will not. What’s the difference? The grit is all silica.”

Natural stones can be different from one side to the other. Go to a stone yard where stone slabs are cut and stacked on end in flitches as they were cut, you will see how dramatically different each slab is, one inch apart.

So not so unusual. It was, perhaps still is a custom for high end Japanese carpenters to buy or commission a new plane blade from a bladesmith and at the smith’s recommendation, buy a stone matched to that particular blade.

We may be able to tell what is in a particular stone, now. But who knows what combination of minerals and other materials over thousands, millions of years created the stone we now hold.

What makes one Pizza better than another, it’s just bread and tomato sauce?
 
The trouble is, if you want sharp, synthetics can get you there easily, and the more you hone the better those edges can get. But shaving is not about sharp, sharp is easy. A .50um stone, film or paste is just more sharpness. A 20-30k or .03um film will exfoliate skin painlessly, (weapers).

Keen and comfortable is the goal. Naturals can give you both, no synthetic can do sharp and comfortable. Paste can get you halfway there, making sharp tolerable, but not like a Natural.
I don't have a lot of experience with natural finishes. My own attempts on an ILR (which, I know, has mixed reviews), nice JNAT edge from a well-respected ebay vendor, and whatever edge Matt W at Griffith put on my Herder (I believe he has a couple of different finishers he uses). But I absolutely agree, all of them, mine included, were delightfully comfortable. Better than what I can do off 1µ or .3µ film, no question. The problem is that none of them were quite sharp enough to comfortably go ATG on the coarsest parts of my chin, and especially under my lower lip. Matt's was the best, but still fell short there. (I wear a mustache, which based on past experience, would be even more challenging to shave ATG). For me, the .5/.25/.1µ diamond pasted balsa progression gives me enough extra keenness to shave the challenging parts with no resistance. If I wasn't shaving my chin I could live with my own ILR finishes, which aren't quite as keen as the others but quite comfortable.

The other side of the coin, as you noted, is that a .3µ film edge is plenty sharp to shave every part of my face, but at a price. Here, the balsa progression serves to mellow that edge out enough to make it tolerable.

Again, it's admittedly a very limited snapshot, but that's been my experience. I have a razor coming that I intend to send to Alfredo; I'm curious to see how his edge measures up.
 
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