Ryan, here’s something that might interest you, a Double Concave JRazor. It’s an auction on Yahoo Japan, and is a shortie, otherwise I might bid on it. I have a similar Aporis and don’t care for it. George Korn also made a double convex razor, but I have not seen one for sale in a condition that I would buy.
YW sir, I wasn’t suggesting that you buy it, but thought that you might like to see the accompanying documents.
Looking closer, it appears to be ground exactly as shown in the picture. It's not really related to this discussion, other than it matches the exaggerated drawings of convex bevels I've seen, only in razor form. That would be an odd razor to shave with. Flexible in the upper part, but with a stiffer edge. Seems like a razor like that could be a bit 'bitey.'
Double Concave Grind, not a Bellied Hollow two different grinds George Korn Patent https://theshaveden.com/forums/threads/american-double-hollow-ground-korn-razor.50415/
Long read ahead. Skip to the bottom for the TLDR. (Stone color in the photograph is not representative of the actual color of the stone) Finally got around to convexing the rest of my slate progression, before I go back to making boxes and working on the translucent Arkansas stones. Honed and shaved off them too. From right to left: 2m Dragon's Tongue 5m Light Green Thuringian 8m Dark Blue Thuringian The Thuringian color names are a bit optimistic, as I have no idea how such things are determined. Some people go by the stone color, others by the slurry color. It only applies to labeled Escher stones, anyways, but we humans like to squirrel everything into a category, so they all get colors now. All I know is that the particle size between the two stones is very consistent and homogeneous, with the dark blue having a particle size half the size of the light green. Another side note: Particle size is not always an indicator of abrasive properties. Some stones with large particles are very fine stones. If I didn't already own the Dragon's Tongue (Aberfellini slate), it probably wouldn't have made it into this progression. This particular stone is fairly quick (for a slate) and, at least on my example, has very inconsistent particle size and leaves a variable depth scratch pattern. A lighter touch might produce better results on that stone. Either way, I wasn't trying to use it as a finisher, so it mattered little to me, and I will probably replace it with some other slate down the road. As another side note, I've discovered that finishing any stone past 400 or so grit is a waste of time, except on fine grained exceptionally hard stones that effectively 'mirror' the last grit used to flatten or shape them (jade, arks, hard Charnley's, hard Turkey's, etc). The natural abrasiveness of the stone will quickly shine through, especially if you sharpen a few kitchen knives on the stone (to remove loose particles, any abrasive sitting proud of the surface, and any remnants of SiC grit) before taking a razor to it. My exposure to different types of stones in the future might eventually cause me to change my mind on this, but for now, this is what I've experienced. Also, what I've experienced is that any sharpening stone can produce a finer edge than the skill of the person doing the sharpening can produce. I suspect that someone with only two stones will learn those two far better than I ever will, with my pile of rocks. Speaking of rocks... The light green thuringian was a bit softer than the dragon's tongue, but harder than the dark blue. It was probably never sold as a razor stone, but as as a tool stone. I suspect it came from just above the blue layers, in a thin spot, as there are bubbles of yellow thuringian in it. A pretty stone when wet, and proof, I suppose, that all thuringians are not finishers. It's probably similar to some of the MST (Mueller) thuris, which can be a bit of a toss up on whether you get a finisher, or pre-finisher stone. Well that, and it's fast and doesn't have any crystalline deposits to pick out. I used it with a rubber (slurry stone) cut from the parent stone and a light misty slurry. It's the only stone of the trio I slurried. Thuringians don't 'need' slurry, per se, as it doesn't really do much of anything. According to what I've read, slurry on these really only affects the feel of steel on stone, and doesn't really affect the edge much in a positive or negative manner. As best I can find out, this is an effect that is unique to thuringians alone. If the corner on mine hadn't been chipped so badly, I probably would have left it well enough alone. Others will probably disagree about my statements regarding slurries on thuringians, that's their prerogative. I read that even heavy thuringian slurries don't seem to have much of an effect on the apex, and my limited experimentation seems to bear that out. It's a good stepping off point for the dark blue thuringian. A noticably softer stone than the light green, and a fine finisher. It produces an easy repeatable edge. It's easy to see why people spend hundreds on an Escher labelled stone. This isn't labeled, but is a good stone, and produces lovely feedback. Both thuringians do, actually. Every honer ought to own at least one, as they are just about the easiest natural stone to finish on. I experimented with both oil and water, previously, and have decided to not use oil on these any more, as due to some quirk of geology, supposedly Thuringians can permanently harden with oil use. Superstition? Old wive's tale? Who knows? As it happens, I prefer the feedback from water better than oil with these anyways. It only took about 15 minutes to go from bevel set to finished edge, all on water. I don't hone particularly fast, either. I'm not convinced that the dragon's tongue has settled down into it's least aggressive self, since it cut faster than usual. I'm not sure if it's because I only went to 400 when shaping it, and a few kitchen knives wasn't enough to smooth it back out yet, or if the stone's 2 meter shape was the reason. Time will tell. It is a fairly hard stone, so I would give equal weight to both options. I switched to the other stones when the razor feel on the stone changed. Coticules are a discussion for another day, and yes, I eventually broke down and convexed one of my coticules. The jury is still out on that one. You know, I really thought the difference in the edge would be subtle, and perhaps for an expert honer, it is. For myself (not an expert), I noticed a huge bump in keenness, and that the edge was more 'skin friendly.' Long term, I'm not sure how the edge will hold up, but I'm impressed with the first shave at least. The previous honing of this razor was done on the flat sides of these same stones, to fairly judge the edge, and I bread-knifed the edge on a glass to ensure I wasn't just refining the previous edge. I'm not a better honer than I was last week, but the razor has a keener edge now in far less time than it took to previously hone it. It was stropped on shell and linen. 6 passes on the linen, and 100 passes on shell. I wish I had the razors and the time to hone on each stone 50 times with a huge variety of razors before I judge it, but I don't. I only have a couple of good razors and some good stones, for certain values of 'good.' Master honers don't typically sell their 'good' stones, only bad ones. If you're lucky, it's the third best duplicate of a favorite stone you can wheedle off them. On the other hand, if they are ethical, they won't ever sell a doorstop. Q: when is the best time to buy stones from a honemeister? A: At his estate sale. In the grand scheme of things, will the shaving world crumble if one mediocre honer (me) gets one good shave off bumpy rocks? No. Or at least, I would hope not. Do I now understand why so many people become 'one shave instant converts to convex honing?' Yes. Am I one? No. Why? Multiple reasons. Ask me again in a year. I'm a long way from judging longevity, edge life, durability, and let's not ever forget Arkansas stones. The amount of time and effort it takes to shape one of those into a curve is just about beyond comprehension, especially if you start off with a rough saw cut slab and have to flatten it first. I know, I know, "you only have to do it once!" Still not worth it. To those who do it out of shear commitment to this style of shaving, instead of curiosity, like me, I salute you. You are a special kind of crazy. This is how it starts, kids. One minute you're talking $#@& about convex hones and six months later your wife will comment that "you are obsessed with hones." My name is Ryan, and I have full-blown H.A.D. (hone acquisition disorder). When I was young, I wanted to be a mineralogist. I even got accepted at Colorado School of Mines. At that time, it cost $60,000 a year, so I didn't go, as I didn't want to be saddled with that much debt. I still have my youthful rock collection, and it's fairly impressive. I really should have seen this coming from a mile away. Probably could have avoided it if I'd gone with synthetics. TLDR: Shaved off a full progression of bumpy rocks once and liked it. Also has full blown HAD symptoms. Also thinks people who convex Arks are crazy.
Moving on to my other set of convexed hones. Top to bottom: 1.7m Belgian Blue Whetstone "la grise" 7m ancient Coticule, unknown vein Flat vintage coticule, "la veinette" The BBW was originally convexed on the 5m plate, with a 1.7m convex Washita being the precursor stone. I have no real reason for changing things up here, other than the fact that the BBW, like the dragon's tongue in my previous post, is not suited for the later stages on honing, and is another stone that is fairly cheap and easy to replace with a much thicker stone of the same type at a later point. Again all honing was done with water. No slurry. Straight strokes on all stones other than the la Veinette, which got elliptical circles instead. Honing continued until the razor started sticking to the stones. This was considerably slower than the previous set of stones, but I'm not sure that's entirely the stone's fault. The razor being honed was a vintage Theirs Issard Spartacus, and those tend to be harder steel than other razors. I understand the modern ones use even harder steel than the vintage ones. I finished with 10 strokes on linen and 100 on shell. Up to this point, I've never gotten a comfortable shaving edge off this razor, which I attribute to my lack of skill in honing. I've owned this razor for around 10 years at this point. I mentioned this once on another forum, and had about ten replies saying a TI Spartacus was one of the user's favorite razors. I also have a kitchen full of Thiers Issard cutlery, so I know they make good steel. The shave was a marked improvement over previous shaves. Not quite as dramatic as the previous shave. I suspect I either need to spend more time on the 7m stone, or go to the Surgical Black after the flat finisher to refine the edge a bit more. The jump from 1.7m to 7m might be a bit much, too. There ought to be a 5m stone in there to lessen the jump. Unlike thuringians and other slates, coticules do have a learning curve, and I'm still learning them. The shave was good, no tugging or pulling, and the edge was skin friendly, but I don't think the blade has been maxed out to it's full potential. Edit: all the cutting action is provided by garnets, and here is one from my personal collection, given to me by my great uncle when I was a child.
Went back and convexed the back of the larger coticule to 5m, and re-honed the razor. After stropping, I tossed it under my cheapo low-resolution scope to see what the bevel looked like now. The amazing .3 megapixel low-resolution image is below, and serves as a reminder that I ought to upgrade my scope soon. About the only thing I can say about it, is that stropping obviously didn't remove the concavity of the bevel, and I seem to have got the progression more or less correct. Edit: ...and that I should probably go longer on the strop. Just for kicks, I also tossed the other razor under the scope. Thuringian edge here. A very different looking edge.
Much better shave today, on par with the slate honed razor. I can see how how repeated honing on convex hones could possibly eventually cause a foil edge on these razors, but the solution seems rather obvious. Just do touch-ups to the edge using a flat hone, and save the convex hones for a full honing session.
One of the problems that I ses pretty often (as problems go) is a razor failing to hold a high grit edge. Geneva, Bartmann, ERN, and these are quality razors. The Bartmann and ERN’s problem is obvious, the spine is way too thin. The Bartmann was just under 14 degrees and the ERN just a little thicker spine.The Nartmann struggles to get a straight, even edge at 8k.The ERN is OK at 8k but won’t take a fine JNat edge. These are both 7/8 razors. I was chatting with a knowledgeable friend, and he’s seen the same thing. He believes that they made the angle too low so that when the bevel has been convexed by the inevitable pasted strops of the day, the razor would shave better than one with the correct angle to begin with. What does this have to do with convex hones? Two things, One, you can always decrease the bevel angle just by thinning the spine. This maybe not what hobbyists would choose to do, but if you’re manufacturing razors it isn’t an issue and apparently they did just that. Two, thinning the steel at the apex is the last thing that you need on many razors.
I'm not seeing much thinning at the apex. Most of the thinning is happening further back from the apex, and I would think that over-thinning at the apex only happens when too much time is spent honing on the larger radii hones. Or too much pressure is used. Or it happens over the course of multiple honing sessions. As for the bevel angle, tape can always be added. Just because most people don't use tape on convex hones doesn't mean it suddenly doesn't work on them. Either way, the one is an issue I haven't ran into yet, and the other is something that is only revealed after time and multiple honings. I'm sure both of these issues are something that @JPO has dealt with before. I remember reading that his first year on convex hones was spent learning how to hone with them, and the last five years have been spent learning how to finesse a longer lasting edge from them.
The only issue I might see is the edge possibly breaking down, because the Convex honing making it a much thinner longer bevel. Just my .02¢ . Ten full shaves, with stropping each time should tell, under the scope, and the feel of the edge on the face. ..
If you can only tell the difference among the best of conditions, and it takes a specific stone of a specific grind and a specific finish, and cannot accommodate thinness at the edge, well, I’m not there.
Are you talking about the super hard steels you occasionally see razor makers turn out? Or the aforementioned Ern's and other razors These are pictures of a before, during, and after of a Dovo (edit: correction, a Böker) at the same magnification (with an attempt to more or less put the blade the same distance from the lens). I'm sure I'll find them a constant source of embarrassment in a few years when my skill improves. I didn't notice a massive increase in the width of the bevel, but I could see the concavity develop, which was interesting to see. Also the amount of effect the flat stone had across the entire bevel, which tells me that concavity isn't very deep at all. Edit: It's hard to emphasize both how little of a change it's making to the bevel, and yet how big the effect of doing so is. Before honing: After 1.7m shape BBW: After 5m shape BBW After 7m coticule (no slurry): After flat coticule (no slurry, elliptical strokes): After stropping on linen and shell: Edit: Definitely using too much pressure on the last stone. I don't think that is typically what is usually meant by "erasing the previous scratches."
This was the last razor I honed using convexed hones. This razor already had a nice edge that was created with flat stones. The goal this time was just to add a little flexibility to the bevel. As I have said before, a small change in the bevel width changes the stiffness noticably. The goal was not to make the razor sharper. These Böker razors can't handle as much refinement as e.g. TI razors. After I was done the razor felt softer and smoother on the face. It was also louder, and had a different sound on the strop. It is like fine tuning the edge to where you want it It is just another tool in the box. Not all my razors are honed this way. My extra hollow ground razors are honed on flat stones. However, if you have not tried a TI razor that is thinned and refined to the maximum, you should. This steel can handle it. I also find the face feel is a little rigid with these razors. Being able to fine tune this by making them more flexible is a big deal to me. Some also have a challenging geometry which is easier to hone on a convex stone. This is just my reasoning for using them. I am not saying everyone should. Saying you don't like something without trying is something different. Good to see you are making progress. You are now in the crosshairs
The edges in the pics above are from a Böker, not a Dovo as I originally stated. I'll be sure to keep an eye on the edge on that one. Although, to be honest, my brother-in-law is likely going to keep the edge on that razor going with flat Arkansas stones. He is perfectly content to sit and hone on the same stone for several hours. For myself, I'm more interested in whether or not the softer steel (compared to Sheffield steel in typical vintage Sheffield made straight razors) of a Rolls blade can hold these kind of edges, and for how long? Yeah, I cannot begin to describe my enthusiasm at being stuck in on the middle of a conflict between Orthodox and Neo honers. 20 or 40 years from now, people will be honing their razors differently than we do now, anyways. 40 years ago, people happily used barber hones. It's the rare shaver now who will use one of those as a finisher on a razor in modern times. 20 years ago, pyramid honing was a thing. Twenty years from now it will be something different that will cause honers everywhere to reach for their blood pressure meds with one hand while they type with the other.
