Convex Hones

I recently deleted a Convex Hones thread I started in here. The basic assumptions I had that convex honing was just a different way to achieve the same results as flat honing were wrong.

Convex honing produces different results. Convex hone enthusiasts claim that the results are superior to those achieved by flat honing.

I am now in the process of doing a deep dive on those concepts, and will be posting either another thread or perhaps even an article on it, once I fully understand the logic and techniques, the historical applications of those techniques, and the results they produce; and can explain it in a way that the average lay person can understand.

I think it's a poorly understood, and perhaps niche technique among straight razor enthusiasts. At this time, I would classify it as an 'advanced' honing technique, that requires a high degree of skill and understanding to master.

I must say that I was disappointed in the reaction elsewhere of convex hone enthusiasts to my actions, but not surprised. When your membership has been ostracized and excluded from the wider forum shaving community for so long, I suppose those kind of vitriol fueled responses are to be expected. A constantly kicked dog will eventually bite the hand that feeds it, after all.


Again, I would like to thank @JPO John for his consummate professionalism in debating with me on the aforementioned thread. He is a shining example of what the wider 'convex hone appreciation crowd' should aspire to, and I've saved his comments to be reposted in a future write-up on convex hones.

Thank you all for your understanding in this matter.

 

I will always seek a deeper understanding of the craft, and all it's applications, even the esoteric and niche elements. We have much to learn from both those who practice the art of shaving now, and those who have been gone for centuries.

I was unwilling to leave a thread up that was posted from wrong assumptions, but at the same time, I'm unwilling to immediately roll over, grovel, and say I was wrong about the validity of convex honing just because I made a wrong assumption. What if that in itself is a wrong assumption?

I was wrong once, and have little desire to be wrong twice, no matter whose feelings it hurts. The naysayers must remain content with my retraction of that thread, and my posting of this one as explanation for my deletion of that thread.

 

I am able to separate the man and his opinions of myself and others from the technique; and the implications of the technique go far beyond fixing warped razors.

Peace, my friend. Do not speak ill of him. He has endured much for his passions and dreams. The scars on his soul are his own to bear.

 

Dalton, I know you and he have a long and colorful history.

Enough.

Evil begets only evil, and I will not see you lower yourself to his level.

 

It's a controversial subject, and that's putting it rather mildly. There are exactly three threads on this forum that discuss them. You're in one. Here's the other two. None cover the subject in the depth it deserves. Once you've read them, click on the video in the first post, then go to that guy's videos starting about five years ago.

Fair warning, he knows his stuff but doesn't exactly explain the history either in those videos. I'm slowly piecing it all together, and will eventually post another thread on the topic. Hopefully it will be a bit less inflammatory than the last one I did.

Have fun diving into that rabbit hole. Don't say I didn't warn you.

https://theshaveden.com/forums/threads/the-jarrod-plate.65110/

https://theshaveden.com/forums/threads/arkansas-convex-hone.61911/

Edit: there's more threads over on Badger & Blade.

 

Presented here is John's information that he discovered about convex hones.

John has described the translation as being the equivalent of someone finding a text written in Shakespearean English, translating it to modern English, and then translating it a third time into another language. This text was translated from Archaic German to modern German, and then into English.

For readability and clarity, I have taken the liberty of re-writing it yet again, which I'm sure some people will view as little less than blasphemy. I will post the original translation in English following this, if anyone wishes to compare this to the translation presented by John. John @JPO was the one who first posted it here. I'll refrain from posting photos of the original German text.

Anytime you see text in [brackets like this] it is something I've added beyond edits for ease of reading. It's usually to add context, speculation, or additional information.

Polytechnische Mittheilungen (Technical/Trade School Communications/Instructions) Vol. 3
Pages 28 & 29

"The blade of a straight razor is unique, different from all other types of knives: A full hollow grind from spine to cutting edge. The thickness of material at the cutting edge is so thin as to be nearly non-existent when compared to the thickness of the spine. There are good reasons for this. After the razor has been completely shaped as much as possible on the grinding wheel, to prepare it for use, it must be honed on a flat oil stone. To do this, the razor must be laid flat on the oil covered stone, letting both the spine and bevel of the razor lay flat upon it. Using light pressure the razor is stroked edge first one way and then flipped and stroked the other way, to prevent a burr from being formed. This must be done as long as necessary. Doing this forms 2 thin (usually 0.2mm to a maximum of 0.6mm wide) bevels, and when those two bevels have been ground down enough to meet at the edge, the bevel (cutting edge) of the razor is set.

Even though the hollow ground sides of the razor don't contribute to the angle of the razor's bevel, they are important. Their hollowness allows the razor to contact the hone at only two points, the spine and bevel, which makes it easy to hold the razor in the correct position. Indeed, the razor almost holds itself in the proper position, because there are only those two points of contact with the stone. The result of this is that the bevel will be even and smooth; a non-hollow ground razor (i.e. a wedge grind) with a thinner spine must be honed with the spine lifted off of the stone. On one hand, this results in an uncertain cutting angle, and on the other hand, even worse, it can form a convex (rounded) bevel, which reduces the keenness of the cutting edge.

If the goal was to create a non-hollow ground razor with a spine so thick it would form a point of contact with the stone when honed in the same manner described above, the blade would need to be ground down evenly along the entire side, adding both to the difficulty and the length of time a worker would need to spend honing the razor, and also introduce the chance that the honer would accidentally lift the spine or bevel slightly off the surface of the stone.

The hollow grind also serves another purpose: it is the reason the bevel coming from the edge of the razor, towards the spine stays the same thickness down the length of the razor. This allows the razor to have both a smooth edge and a very small bevel. This makes it both easier and faster to hone.

The stone used for honing has to be hard, with very dense structure and with fine and evenly distributed grit, because without these characteristics there is no way a smooth cutting edge can be produced. [Note: this likely refers to a Thuringian type of stone like Escher, though the description fits a number of natural stones].

Some use 2 or 3 stones with a graduation in the fineness of grit; without a doubt, the person who only uses one single very fine grained stone, though they spend more time honing, will eventually produce a very smooth edge. This might even be better than using a progression of finer and finer grit stones because the deeper scratches [Note: stria or striations] left from the previous larger grits won't need to be polished out.

Other honers even take the further step of altering the surface of their progressive grit sized stones. A well trained and experienced razor honer once told me that he used a more advantageous way of honing:

The first stone he used, which cut the fastest, [Note: We would call this a 'bevel setting stone'] which can be either a water or oil stone, should have a convex surface.

The second stone in his arsenal, is described as a 'levantinian oilstone' or 'oilstone from the lands of the Levant' [Note: this referred to the non-muslim regions of the Middle East, including the present day countries of Syria, Lebanon, Jordan, Palestine, and Isreal; this was likely a mid grit stone, perhaps even what we know today as Turkey Stone, even though we know it was quarried in Crete, not Turkey] was prepared in the same way, but less convex than the first stone.

The third and last stone should be flat, and a hard and fine clay based blue slate stone should be chosen, [Note: This likely refers to a hard Blue Escher or Thuringian type of finishing stone] and only water should be used on this stone during honing.

This is the logical method of honing; the convexness of the first two stones will thin the steel near the bevel progressively, and by the time the razor reaches the last stone, the extremely thin bevel takes very little time or work to refine.

I have my doubts [as to the usefulness of this method (implied by the context)], as honing on convex stones requires more experience than even the years of training and experience needed for honing on flat stones.

As a matter of fact, this process of honing on convex stones, as far as I know, is only used by knifemakers, knivegrinders and barbers.

Even after honing, the edge of the razor is not suitable for shaving until it has been stropped to remove the last of the roughness left over from honing. As everyone knows, this is done by using a hanging strop made from calf hide (veal) or a Russian Leather strop. [Note: given the age of the document, this would be genuine 'Russian leather,' which is to say that it would be vegetable tanned in a birch bark tanning solution, using methods that have only recently been rediscovered, having been lost since shortly after the 1918 Russian Revolution. The hair side of the strop would have had a crosshatched pattern of cuts to allow the tanning to penetrate more fully into the leather. Modern Russian leather strops today only imitate the look, not the actuality of vintage Russian leather] The flesh (smooth) sides of the strop would be used. One side being prepared with a red honing compound, and the other side with a black honing compound. These compounds were a mixture of fine honing powders and fat." (polishing red/kolkothar, and black lead/graphite)
[Note: Dovo still sells these compounds today].

Edit: there are other historical references, found by Jarrod, as well as Jarrod's personal journey into convex hones. That particular story will be told in a future thread as well. I'll try not to mess it up again.

 

Well there's a lot to unpack here, and I wasn't really wanting to go into this until I was ready to, and I'll say it flat out, that I'm not as prepared or qualified to answer these questions as I would like to be, yet.

So here goes.

Yes. It does create a convex bevel. The logic, science, and math all support the concept.

A keener edge cuts better. A more flexible edge follows the contours of the face better, theoretically allowing for a closer shave than a traditionally honed razor. As for it being a better shave? No clue. It's like the feather DE blade argument, most people probably won't benefit from something that sharp, and might even find it more uncomfortable. Then there's the other group of people who won't settle for anything less than a Feather edge.

From the historical record, even among those who were considered expert honers, honing on convex stones was considered an advanced honing technique, and at one time this was considered common knowledge, known to all in the razor grinding craft; even though it was seldom practiced by those in the craft, due to the extra degree of skill and years of training required to consistently hone such an edge. A convex honer needs to constantly check to ensure an even bevel is being maintained. A barber, honing on a flat stone, doesn't need to do that, and frankly, doesn't have the time to learn to do that.

If the concavity is done correctly to the razor, the strop should only touch the last 20% of the bevel, and that is such as small area, flattening it out or even convexing it shouldn't effect the cutting ability of the edge. You really should be using a cased (i.e. pressure treated) hard surfaced strop (like a vintage shell strop) for this type of edge, and I suspect that a softer strop, like balsa or roo leather, will undo much of the work that someone puts into honing such an edge.
[Edit: perhaps the edge is flexible enough to 'float' over the surface of a softer strop. I really don't know. Edit 2: I wouldn't think a pasted strop should be used]

Same reason one strops off of flat rocks. To smooth out that edge and remove micro burrs.

Hey, that was my argument too!

The simple answer is this, so the edge will last longer, and the blade is so thin it doesn't require the mechanical advantage of a concave bevel.

Dovo would probably argue that they produce a razor that is ready to be honed to the end user's preferences. That is my speculation, and anything I said beyond that would also be speculation.

I think it's safe to say that they do use a convex hone. Thiers-Issard does too, judging by the marks left behind the bevel on brand new razors. They aren't as careful to polish them out as the Germans.

The old texts clearly indicate that convex honing was a highly advanced skill. Constant monitoring is required to keep the bevel width consistent and even. The toe and heel will get less attention than the center of the blade if a person isn't paying attention. Sloppy work on a convex hone will eventually produce a frowning blade. The amateur honer has one advantage the old honers didn't have. A sharpie. Marking up the bevel and observing the results of honing ought to take some of the skill and practice required to use a convex hone out of the equation, but no, I wouldn't call it a easier method of honing. Quite the opposite in fact.

I agree. ...and I would hesitate to call my answers here "qualified." More along the lines of "reasonable assumptions," without experience to back them up, only logic.

Edit: The only "FACT" that we can all be sure of is that the concavity imparted by all of the convex stones on a razor's bevel is measured in microns. It is logical to assume that a strop will erase that concavity. At the end of the day, the main question that needs to be answered is really going to be, "does the strop impart as much convexity to the edge as it does to a razor coming off a flat hone?" And "Does the strop erase the thinness of the edge as created by the hones?"

If the answer is "yes," then convex hones are a waste of time, and all the theory in the world won't support cold hard reality.

If the answer is "no," then convex hones deserve to be an accepted part of a honer's arsenal, for those few who require the keenest edge.

 

Shower thought for the day: Both the Twinplex stropper and the Shake Sharp razor operate by using convex honing principles.

But... Does the improved shave come from the honing/stropping action? Or from the convexity imparted to the edge? Or a combination of the two?

 

The math does not support that argument. As personally irritating as I find Jarrod's sarcasm and delivery, the counter argument and math presented in this video checks out.

The math changes slightly depending on both the arc of the hone and the width of the razor, but in reality you are dealing with around 40-50 microns of concavity in the bevel per side. (Edit: and a 1mm bevel is widened by about 20%, to 1.2mm by this process).

The concavity approaches the edge of the razor, but does not actually touch it, so the edge sharpness is not affected by the concavity. The last little bit of the bevel (about 20%) is being presented to the final hone/strop untouched, so the whole basis of that part of your argument gets thrown out the window.

We both agree on that point.

I can only speak for the historical record. Those men are all dead, so we can't ask them to explain themselves better, but yes, it was strongly implied that this was a very advanced technique, only used by razor grinders, knife makers and scissor makers, and not even by most of them.

I cannot speak for what others might say about the ease of honing on convex stones.

Edit: I probably can't feel the effect of concavity of approximately 1/2 of one tenth of a millimeter per side. But I won't deny that there are probably some people who are sensitive enough to feel that difference, and appreciate it.