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Convex Hones Rethought

Over the years I have pondered the pros and cons of using a convex hone to produce an exceptional straight razor edge. Indeed it is more than a “Ford-Chevy….Tastes great, less filling“ difference of opinions.
When the convex hones first appeared on the horizon, I’ll admit I was a tad skeptical. I wasn’t sure if this was a clever new method of sharpening, re-introduction of old and established technique, or something epic and wonderful. My first impressions were “meh”.
As time went on though, it seemed perhaps I was missing something with the convex hones and the edges they reportedly can produce. So…..without rehashing history in detail:
My first experience with the new edge created on a convex hone may not have been the greatest. But, that could have been due to myriad variables. Point being, there are a lot of positive reports about this technique and its ability to do good things to a razor. Figured I’d give it another try. This time I was giving the green light to Jarrod at TSS and asking him to put the convex mojo on a new, never before honed outside the factory, Thiers-Issard 6/8 extra full hollow.
And…….
OK, I get it. Cutting right to the chase I can say this T-I offered up one truly fine shave on a multi-day growth. Close and comfortable…to say the least. I was so impressed, I bought a second razor (Dovo Bismarck 6/8 full hollow) and asked Jarrod to set that one up on the convex stone as well. Yeah, I was that impressed.
I’m now considering buying one of the plates TSS sells to reshape a flat stone to convex.
I have a set of Jonathan Coe Arkansas stones that I believe would work even better once reshaped.
I‘m curious to see how honing a quarter or half hollow grind blade might work on a convex hone. It’s my understanding they perform at their peak on hollow or extra hollow grinds. I will have to look into that in the future.
 
You could ask Jon his thoughts about using his stone in such a manner. I’m sure he’d give ya some feedback. I love the couple I have.
 
I have a few stones I accidentally made convex becuase of my granite base plate, which started flat long ago is now slightly concave. The slightly convex stones work really nice for knives, I think it speeds the stone up from smaller point of contact and increased pressure. My convex washita is very nice and will not need to be lapped again for longer than if made dead flat to start, which is a big plus since it is used often.

I attempted to use them for razors and was not very satisfied. I spent alot of time trying to ensure the entire bevel edge was getting equal work and adjusting my honing strokes. My normal techniques seemed less than satisfactory. Maybe if I had as much experience with the convex stones things would feel better but ive already spent too much time with flat stones I think.

I would guess Jarrod's honing experience plus nice new razors contribute primarly to the wonderful shaves more than the convexed stone? Maybe ill have to test mine out again, I had considered making a Thuringian convex to see if it would speed up.
 
I’m sure Jarrod’s expertise would come into play regardless of what one was trying to hone and how. He’s good enough to take a popsicle stick and put a shave ready edge on it using a chunk of concrete.
As far as the newness of the razor being honed…I would think not.
As long as the blade is straight and free from any glaring flaws, I’d say as nice an edge could be created as one on a brand new razor of quality manufacture.
 
Always thought it would be a fun project to dabble/experiment with convex hones. One of these days when I have the time and the disposable income again. If you can, give us a quick update once you experiemnt more with a quarter and a half hollow blade. Curious about the results.



With that though, t's amazing/sickening how toxic the subject became in the honing community.
 

Steve56

Ask me about shaving naked!
With that though, t's amazing/sickening how toxic the subject became in the honing community.

It isn’t convex hones that are toxic, it’s the antics of a very few people who promote them for notoriety or profit, and ‘talk down’ to people who question them or disagree. That’s where the toxicity is, not in the stone shape.

Convexity was known to Iwasaki back in the 60s too, he knew that if you lapped a stone on loose grit like SiC, it would have a slight crown on it. He mentions this in his chapter on barbering in his book. He did not recommend honing on a convex stone (or advise against it for that matter).
 
It isn’t convex hones that are toxic, it’s the antics of a very few people who promote them for notoriety or profit, and ‘talk down’ to people who question them or disagree. That’s where the toxicity is, not in the stone shape.

Convexity was known to Iwasaki back in the 60s too, he knew that if you lapped a stone on loose grit like SiC, it would have a slight crown on it. He mentions this in his chapter on barbering in his book. He did not recommend honing on a convex stone (or advise against it for that matter).

I think he was adamant about having a flat hone. Although the amount of convexity produced by lapping on loose abrasive on a flat surface is minimal compared to something produced by TSS lapping plates. I’ve been watching Gary Haywood’s YT channel and he seems pretty convinced the convex hones give him a better shave. Lends some credence to the theory imo.

Excerpt from Honing Razors and Nihon Kamisori:

806DF5C1-5BF2-4A72-AEDE-9C63066BEBED.png
 
Well…this I know.
I was slow to get on the convex hone wagon but after using a razor properly honed by a guy who knows what he’s doing with convex hones I’ll say the end game is a very pleasant, close, and all around nice shave. And that’s all I’m looking for.
There is a lot of science and geometry surrounding the philosophy of convex vs flat hones. That’s a fact. All I know is that the convex hone school works for me.
 
Well…this I know.
I was slow to get on the convex hone wagon but after using a razor properly honed by a guy who knows what he’s doing with convex hones I’ll say the end game is a very pleasant, close, and all around nice shave. And that’s all I’m looking for.
There is a lot of science and geometry surrounding the philosophy of convex vs flat hones. That’s a fact. All I know is that the convex hone school works for me.
Devil's advocate, for a moment: is it possible that Jarrod just hones a really nice edge?

I have no skin in the game here, from a theoretical perspective a convexed hone makes sense. Whether it is truly a gamechanger in practice, I don't know. Not ruling it out. I know there are guys here who swear by it.

I'm really interested in hearing how this goes in your own honing.
 
Well…this I know.
I was slow to get on the convex hone wagon but after using a razor properly honed by a guy who knows what he’s doing with convex hones I’ll say the end game is a very pleasant, close, and all around nice shave. And that’s all I’m looking for.
There is a lot of science and geometry surrounding the philosophy of convex vs flat hones. That’s a fact. All I know is that the convex hone school works for me.

In theory a flat hone will produce an apex consisting of two flat planes intersecting.

In theory a convex hone will produce two concave planes intersecting at an apex.

The whole "arguing" going on in the forums is whether, in real world circumstances, these events occur, and if they do occur, is the result noticeable.

I have played around with convex hones and from observation under magnification imo it does impart a concave bevel plane.

I am undetermined about whether the shave was "better" enough to make the effort worth it. Sometimes the edge seemed better, sometimes about the same as a traditional flat honing.
 
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Steve56

Ask me about shaving naked!
Well…this I know.
I was slow to get on the convex hone wagon but after using a razor properly honed by a guy who knows what he’s doing with convex hones I’ll say the end game is a very pleasant, close, and all around nice shave. And that’s all I’m looking for.
There is a lot of science and geometry surrounding the philosophy of convex vs flat hones. That’s a fact. All I know is that the convex hone school works for me.

At the risk of introducing a controversial name, Jarrod has always been a first class razor honer, even before the convex stones. He doesn’t need a convex hone to make a great razor edge, he has the chops. Credit where credit is due my friends! But if you think that his edges are the result of hone shape rather than honing skill … well no comment.
 
I bought my first new razor from Jarrod - a Dovo Carre - shaves great. No idea if Jarrod did or did not use a convex stone. I have also shaved with edges from Alfredo and a few of mine that were honed on flat hones that shave great. My guess is you can also get a great edge (and shave) from other shaped hones as long as you got the chops.
 
The hone is more attributable to the honer‘s skills rather than the stones or materials being used in my humble opinion. I’ve had buddies produce crap edges with amazing perfectly flat stones and others who could use sandstone from a creek bed to generate an amazing edge. My unorthodox kit yields me great results yet others would say no way. Practice and familiarity with the stones being used yields the end result.
E6492DD6-E17B-48A7-B2C2-9399088586AE.jpeg
 
To me it is not flat vs convex. I use both for different circumstances. It is more interesting to learn more about how people are using them, not if it is better then anything else.
First of all if you want to actually try it you have to invest some time and actually try it. Creating one stone with one large curvature and saying it did not work for you is like saying you tried the "Method" edge, but you skipped to the end.

First of all the bevel setting/shaping stone is the most important stone. This stone needs to have a relatively small wheel radius. Mine is 1.5-2 m. For some razors that might be to much. So a little trial and error is expected. This radius works really well for 6/8" razors. You will end up with a taller bevel. If you are after a "nice" narrow bevel i suggest you stick to your flat stones.

The next stone is a transition stone that needs to have a larger radius. I use a coticule. Staying on this stone to long you risk doing to much work and loosing some of the extra bevel height you ended up with on step one. Again, trial and error. The feedback from a coticule is really easy to read when used this way.

If the geometry is ok i finish on a flat stone, just like Garry did in his videos.
The most interesting aspect of this final stage, for me at least, is what happens if you take a concave bevel and finish on a flat JNAT with slurry. Some of the slurry seems to get trapped in that void/concavity and continues to work on the bevel plane and the apex. This makes a noticeable difference in the final edge for me. I am still trying to wrap my head around what is going on here.

A different way i use a convex hone that work fine is to do a coticule dilucot with e.g. two coticules. Do a full dilucot down to clear water on a flat stone. Create a small "back bevel" on a convex stone. You only need one with a large wheel radius for this. Go back to your flat stone and finish. You will gain a small advantage by changing the angle of the bevel to enable better contact with the end of the bevel. You now sort of bridge the gap a little because the garnets in the coticule do not brake down, making the transition from slurry to water difficult on some stones. You will probably not gain much with respect to getting a thinner bevel, but i can at least get a small advantage this way. Some coticule edges just needs a little extra to go from good to grate.

I tried making making sense of this by doing calculations, and it did not make sense to me, so i understand why some are not convinced. There is allot more going on then just simple geometry. Trying to make science out of this is just derailing the core of the subject. An practical real effort is required. You will not be convinced behind a keyboard.
 
To me it is not flat vs convex. I use both for different circumstances. It is more interesting to learn more about how people are using them, not if it is better then anything else.
First of all if you want to actually try it you have to invest some time and actually try it. Creating one stone with one large curvature and saying it did not work for you is like saying you tried the "Method" edge, but you skipped to the end.

First of all the bevel setting/shaping stone is the most important stone. This stone needs to have a relatively small wheel radius. Mine is 1.5-2 m. For some razors that might be to much. So a little trial and error is expected. This radius works really well for 6/8" razors. You will end up with a taller bevel. If you are after a "nice" narrow bevel i suggest you stick to your flat stones.

The next stone is a transition stone that needs to have a larger radius. I use a coticule. Staying on this stone to long you risk doing to much work and loosing some of the extra bevel height you ended up with on step one. Again, trial and error. The feedback from a coticule is really easy to read when used this way.

If the geometry is ok i finish on a flat stone, just like Garry did in his videos.
The most interesting aspect of this final stage, for me at least, is what happens if you take a concave bevel and finish on a flat JNAT with slurry. Some of the slurry seems to get trapped in that void/concavity and continues to work on the bevel plane and the apex. This makes a noticeable difference in the final edge for me. I am still trying to wrap my head around what is going on here.

A different way i use a convex hone that work fine is to do a coticule dilucot with e.g. two coticules. Do a full dilucot down to clear water on a flat stone. Create a small "back bevel" on a convex stone. You only need one with a large wheel radius for this. Go back to your flat stone and finish. You will gain a small advantage by changing the angle of the bevel to enable better contact with the end of the bevel. You now sort of bridge the gap a little because the garnets in the coticule do not brake down, making the transition from slurry to water difficult on some stones. You will probably not gain much with respect to getting a thinner bevel, but i can at least get a small advantage this way. Some coticule edges just needs a little extra to go from good to grate.

I tried making making sense of this by doing calculations, and it did not make sense to me, so i understand why some are not convinced. There is allot more going on then just simple geometry. Trying to make science out of this is just derailing the core of the subject. An practical real effort is required. You will not be convinced behind a keyboard.


I don't think it's an exaggeration to say that the primary individual who promotes convex honing would in fact stress that it creates "better" edges, all else equal. I am totally agnostic on that matter.

I shaped a whole set of Nortons (1K, 4K, 8K) to the short axis of the spherically convex plate which was a 6' diameter wheel; since I liked to have the whole bevel plane polished and at it's maximum concavity, then I would go right to a flat finisher, an ark or a little thuri I have kicking around.

I've got more fond of heavier grinds in the recent past, I have honed a wedge on convex stones, it still works (ie, produces a sharp razor with a concave bevel) if you don't care about scratching up on the face of the blade (I don't). But it really is more optimized for full hollow imo, there's so much meat behind the edge on heavier grinds you won't get anywhere near the flexibility advantage of bevel thinning.

The funny thing is that there is literature on convex honing going back to the middle 19th century when all one could really get for the most part was a wedge. There's some information missing imo. Apparently the technique was pioneered in England and then went to Europe but all the English literature I could find on honing going back to the mid to early 19th century is adamant on having a flat hone. More investigating required.

I think I'm just not in that place where I want to put a lot of effort into honing tbh. Trying to simplify my routine hence a recent coti purchase to go back to where I started, getting a good bevel set on a 1/2K stone then using dilucot/unicot and all that. I'll still keep a few other finishers around but having a progression through multiple grits is not on my cards these days.

I think Arks are probably the optimal stone for convexing since they barely wear so you only have to put the effort in once, I really didn't want to put the 12" soft and 11.5" hard arks I had at the time on the plate.

All sorts of techniques are contentious but as long as one is getting a sharp, shaveable edge, do whatever you need to do.

P.S.

Anyone who wants an absolute bargain on some convex Nortons and a TSS lapping plate, PM me.
 
The funny thing is that there is literature on convex honing going back to the middle 19th century when all one could really get for the most part was a wedge. There's some information missing imo. Apparently the technique was pioneered in England and then went to Europe but all the English literature I could find on honing going back to the mid to early 19th century is adamant on having a flat hone. More investigating required.
Coming at this as a complete amateur, but somebody who is well read in history; you generally have to consider the whole situation at a particular time period to unpack missing information. Razors were produced more commonly, as far as I know, than today. So the manufacturers were closer presumably. Is it possible one of two scenarios fits? One: the razor was semi disposable in the sense that it was taken out of service once a bevel couldn't be maintained easily, meaning they didn't do major bevel resets. Two; more plausible, the razor was simply sent back to somebody with a wheel to be reground and the user was only expected to use a flat hone to maintain the razor for however long that would last. There are things that might be classified institutional knowledge that don't get written down; you take your razor to the barber to have it honed, he hones his own razors. If he wasn't doing bevel resets himself, that wouldn't be the kind of thing I would expect to be written down, he would just know where to take it in his local area. I always wondered how barbers only had one "barber stone?"

Sorry if this useless rambling...
 
Coming at this as a complete amateur, but somebody who is well read in history; you generally have to consider the whole situation at a particular time period to unpack missing information. Razors were produced more commonly, as far as I know, than today. So the manufacturers were closer presumably. Is it possible one of two scenarios fits? One: the razor was semi disposable in the sense that it was taken out of service once a bevel couldn't be maintained easily, meaning they didn't do major bevel resets. Two; more plausible, the razor was simply sent back to somebody with a wheel to be reground and the user was only expected to use a flat hone to maintain the razor for however long that would last. There are things that might be classified institutional knowledge that don't get written down; you take your razor to the barber to have it honed, he hones his own razors. If he wasn't doing bevel resets himself, that wouldn't be the kind of thing I would expect to be written down, he would just know where to take it in his local area. I always wondered how barbers only had one "barber stone?"

Sorry if this useless rambling...

I have an excerpt here from a text in a book called the Encyclopedia of Mechanical Arts (or something similar) where they have a whole couple pages on the manufacture of razors in Sheffield and the observer specifically describes the hones as being flat. We know this is in a factory setting because he specifically mentions "a new razor or and old one just ground" and striking off the burr after grinding and glazing which would only be something that occurs in a factory. Notice also the words, "perfectly flat", quite precise use of language imo.

Razor Hone.png


There is more on the subject in German which is where the technique is/has been more common in the recent past. I did some translation myself a while ago on another forum.
 
This is some text I translated out of German from a book called Polytechnische Mittheilungen published in 1846 I posted over at SRP a while back.

In English:
"the stone intended for sharpening the razor must be hard, with a very fine, uniform and dense grain, because without these properties it can never produce a properly fine cutting edge.
some apply two or three stones of gradually increasing fineness of the korus one after the other; It is certain, however, that you can always achieve your goal on a single, very fine stone - perhaps with a little more expenditure of time - probably even to the advantage of the cutting edge, because you do not expose yourself to the need to first work through the roughness caused by the rough stone to devour the finer.
Others go even further by giving the successive stones a different shape. In particular, an experienced man praised the following procedure as being very beneficial: the first, sharpest stone (which can be an oil or a water stone) should be given a convex shape; just like that, but to a lesser extent, the second, who is a Levantic oelstein; only the third (last) stone has to be completely flat, and for this you choose a fine, hard slate of clay (blue whetstone) on which you always have to pull it off with water.
this method is efficient; because through the convexity of the first two whetstones it causes a successive thinning of the knife in the vicinity of the cutting edge, consequently means that at the end of the day the flat stone only produces exceptionally narrow facets and its work is completed quickly: I only believe that the machining on the convex stones will require even more skill than honing the already difficult task on a flat stone. In fact, as far as I know, the latter is found exclusively in use by knife manufacturers, knife sharpeners and barbers. "

In German:
"der zum abziehen der rasiermesser bestimmte stein muss hart, dabei vou sehr feinem gleichformigen und dichten korne sein, weil er ohne diese eingenschaften niemals eine gehorig feine schneide zu erzeugen vermag.
manche wenden zwei oder drei steine vou stufenweise zunehmender feinheit des korus nach einander an; es ist aber gewiss, dass man auf einem einzigen ganz feine stein - vielleicht mit etwas mehr zeitaufwand - jederzeit zum ziele kommt, wohl sogar zum vortheil der schneide , weil man sich micht der nothwendigkeit aussetz, die von dem grobern steine verursachten rauhigkeiten erst wieder durch den feinern zu vertilgen.
andere gehen noch weiter, indem sie den auf einander folgenden steinen auch eine verschiedene gestalt geben. namentlich ist mir von einem ertahrenen manne folgendes verfahren als sehr vortheilhaft geruhmt worden: man soll dem ersten, scharfsten steine (weicher ein oel-oder ein wasserstein sein kaun) eine konvex-gekrummte gestalt geben; eben so, jedoch in minderem grade, dem zweiten, der ein levantischer oelstein ist; nur der dritte (letze) stein musse gauz eben sein, und hierzu wahle man einen feinen harten thonschiefer (blauen schleifstein) auf dem das abziehen stets mit wasser zu geschehen hat.
rationell ist diese methode; denn sie bewirkt durch die konvexitat der ersten beiden abziehsteine eine successive verdunnuug des messers in der nahe der schneide, macht folglich, dass zuletz der flache stein nur ausserat schmale facetten hervorbringt und seine arbeit schnell vollendet: ich glaube nur, dass die bearbeitung auf den konvexen steinen noch mehr geschicklichkeit erforden wird, als das schon gennngsam schwierige abziehen auf einem flachen steine. in der that findet man den letztern, so viel mir bekannt, ausschliesslich im gebrauch bei den messerfabrikauten, messerschleifern und barbieren."
 
Well at least my stupid comment led to useful information. Now I know where Jarrod got some of the information I read, it's almost word for word. Very interesting, thank you. I will go back in my corner now.
 
It is, in my opinion, extremely silly to get into arguments on this subject. Do what works for you. If that means you hone upside down in outer space on a pyramid shaped piece of sandpaper using butter for a lubricant - and you get a good shaving edge - then do that. To espouse one method as better than the rest for everyone else doesn't make any sense. It's sort of like trying to push your religion on someone. It might not fit.

Getting a good shaving edge is the important thing. Most of the rest is subjective. There is very little distinction between a really good edge between the better stones, regardless of the method used: flat stone, convex stone, etc. A really good pasted strop/balsa edge can "edge":) out a really good stone edge sometimes but they are not nearly as forgiving either. But a lot of that comes down to shave technique and experience.

In the end, what that means is: personal preference is a factor for every one of us.
 
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