Wait, what ?? Straights needs to "rest"??
- Thread starter Bbb34
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You know what's truly hilarious about this whole thread?
I know just enough ferrous metallurgy that I could make a factually accurate and convincing argument that the edge of your razor would technically benefit from a "rest" period measured in multiple days after shaving before being stropped.
Not that the incredibly tiny "benefit" would manifest in real world use, but it -is- technically there...
I know just enough ferrous metallurgy that I could make a factually accurate and convincing argument that the edge of your razor would technically benefit from a "rest" period measured in multiple days after shaving before being stropped.
Not that the incredibly tiny "benefit" would manifest in real world use, but it -is- technically there...
I'd be interested in listening.
lol - I'll try it without diagrams, but it would be easier to illustrate.
When you shave, you deflect the edge a tiny bit out of straight. This deflection is why stropping helps restore a razor that is a bit "harsh" after shaving to good, smooth shaving condition.
That deflection, at an atomic level, is stress in the crystalline structure. It represents a plastic deformation due to the stretching of material on the outside radius of the curve. When you bend steel, you are not compressing the interior radius of the bend even a little, all of the bending comes from stretching the outside radius of the curve.
We view those plastic deformations as permanent bends. However, some small percentage of that bend does "walk back" towards original position over time. This happens as the stress caused in the stretching along the outside radius relaxes slightly, which causes some small bit of that stretch to return towards original alignment.
To more clearly illustrate this principal, take a paperclip, or a plastic pen cap. Bend it. Then let go. You will notice that it immediately springs back a bit, but not nearly all the way. However, if you watch closely, you will see that it doesn't quite -stop- immediately, it will VERY slowly continue a SMALL bit more movement towards where it started. That movement is already incredibly slow, and it continues to slow down even more. If you freshly bend a paperclip, then put it on a piece of white paper and put an ink dot at the end of the bend, then leave it undisturbed for 2-3 days, you should be able to notice a TINY amount of motion because the end of the paperclip will not be pointing EXACTLY at that dot anymore.
When we strop right after shaving, we haven't given those stretch stresses time to relax the edge as much closer towards straight as they are eventually going to. Instead, we mechanically push the edge closer to straight, which, in fact, does the opposite. Instead of relaxing those stresses, we are introducing equal, reciprocal stresses on the other side.
This difference is incredibly tiny. Given the fineness of a razor's edge, and the tiny amount of deflection originally, we're talking about fractions of a nanometer. A small percentage of an already tiny motion on an incredibly finely polished edge. In practice, you could have two identical razors, honed by the same person on the same hones, and both shaved with daily by the same shaver who switches which one shaves the left vs right sides of his face every other day, with the only difference being one is always stropped right after shaving, the other always right before (and thus rested 24 hours), and over that person's lifetime the difference doesn't add up to a noticeable margin.
It exists - it just doesn't matter for the use we're putting the metal.
When you shave, you deflect the edge a tiny bit out of straight. This deflection is why stropping helps restore a razor that is a bit "harsh" after shaving to good, smooth shaving condition.
That deflection, at an atomic level, is stress in the crystalline structure. It represents a plastic deformation due to the stretching of material on the outside radius of the curve. When you bend steel, you are not compressing the interior radius of the bend even a little, all of the bending comes from stretching the outside radius of the curve.
We view those plastic deformations as permanent bends. However, some small percentage of that bend does "walk back" towards original position over time. This happens as the stress caused in the stretching along the outside radius relaxes slightly, which causes some small bit of that stretch to return towards original alignment.
To more clearly illustrate this principal, take a paperclip, or a plastic pen cap. Bend it. Then let go. You will notice that it immediately springs back a bit, but not nearly all the way. However, if you watch closely, you will see that it doesn't quite -stop- immediately, it will VERY slowly continue a SMALL bit more movement towards where it started. That movement is already incredibly slow, and it continues to slow down even more. If you freshly bend a paperclip, then put it on a piece of white paper and put an ink dot at the end of the bend, then leave it undisturbed for 2-3 days, you should be able to notice a TINY amount of motion because the end of the paperclip will not be pointing EXACTLY at that dot anymore.
When we strop right after shaving, we haven't given those stretch stresses time to relax the edge as much closer towards straight as they are eventually going to. Instead, we mechanically push the edge closer to straight, which, in fact, does the opposite. Instead of relaxing those stresses, we are introducing equal, reciprocal stresses on the other side.
This difference is incredibly tiny. Given the fineness of a razor's edge, and the tiny amount of deflection originally, we're talking about fractions of a nanometer. A small percentage of an already tiny motion on an incredibly finely polished edge. In practice, you could have two identical razors, honed by the same person on the same hones, and both shaved with daily by the same shaver who switches which one shaves the left vs right sides of his face every other day, with the only difference being one is always stropped right after shaving, the other always right before (and thus rested 24 hours), and over that person's lifetime the difference doesn't add up to a noticeable margin.
It exists - it just doesn't matter for the use we're putting the metal.
Thank you.
But these plastic deformations only happen if we are exceeding the yield stress, correct? My assumption would be that because of the thinness of the section, the edge could deflect relatively far [farther than the cutting action would produce] without exceeding yield.
Please take this as all constructive and interesting discussion and not an argument. I've worked with steel all of my life and truly do find this interesting. I also agree that the microscopic differences that we are talking about would have no practical effect. I always strop directly before and after shaving.
I have a pet theory that the un stropped edge could oxidize slightly during the 'rest' period and then be removed on the next pre shave stropping which would sharpen the edge. I also think that we could find iron oxide, a fine abrasive, in our leather strops if we looked for it from this same oxidation removal.
But these plastic deformations only happen if we are exceeding the yield stress, correct? My assumption would be that because of the thinness of the section, the edge could deflect relatively far [farther than the cutting action would produce] without exceeding yield.
Please take this as all constructive and interesting discussion and not an argument. I've worked with steel all of my life and truly do find this interesting. I also agree that the microscopic differences that we are talking about would have no practical effect. I always strop directly before and after shaving.
I have a pet theory that the un stropped edge could oxidize slightly during the 'rest' period and then be removed on the next pre shave stropping which would sharpen the edge. I also think that we could find iron oxide, a fine abrasive, in our leather strops if we looked for it from this same oxidation removal.
Guys - you are all off - this simple equation proves it.
Both of your theories RE: oxidation are in fact correct, though the sharpening effect of removing oxidation are similarly very tiny.
If you look at a blade that has been shaved with under a microscope, you can see the deformations, subtle though they may be. The thinness of the section really does help, but it would just flex back to shape if some portion did not stress at yield.
When you add load to steel, as I'm sure you're aware, and you hit yield strength, it typically has a broad range of deforming with almost no additional force before it suddenly snaps - that range is where we're working.
Well, it's been a while since I've looked at SEM pictures of edges after shaving, but I agree if they show deformation then the steel has been pushed past yield. I suppose that any amount of recovery over time would minimize the work hardening and subsequent failure.
Thanks for the conversation.
Even at fairly high magnification, they are subtle, and it helps if there's been more than one shave, but yeah, after even one you can sometimes tell.
Thanks, It was stimulating, and entertaining, unfortunately, it is ultimately meaningless for practical purposes.
I watched this thread develop with some level of amusement, waiting for someone else to come in and drop the "well, actually" bomb. When it became clear that level heads had prevailed, I had to stir the pot a little.
Thanks, It was stimulating, and entertaining, unfortunately, it is ultimately meaningless for practical purposes.
I watched this thread develop with some level of amusement, waiting for someone else to come in and drop the "well, actually" bomb. When it became clear that level heads had prevailed, I had to stir the pot a little.
My poor kitchen knife.
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