Thread: Verhoeven Paper Question

A lot of long posts in this thread. So far, as I've read, I think there is consensus that the leather strop will align the distal edge of the razor. Will the strop also draw out, pull out, or for lack of better terminology *stretch* the extremely thin distal edge to an even thinner and final, keen shaving edge? Is that possible or not?


Scott

Originally Posted by honedright

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Will the strop also draw out, pull out, or for lack of better terminology *stretch* the extremely thin distal edge to an even thinner and final, keen shaving edge? Is that possible or not?


Scott

I think it may be possible; limited by the particular steel's ability to repeatedly bend over an ≈ 15 degree arc, from each stropping stroke, without breaking off. I am just guessing.

I think the strop also "fills in" and sharpens the corners and "radius edges" of the microscopic nicks and other damage in the cutting edge. I mean the damage done by our hairs or micro-rust that results from normal shaving. Still guessing.

I don't think the leather strop does anything but align the edge. Neither Verhoeven nor the Modern Mechanics article from the 20's showed any sort of steel flow or stretching. Verhoeven also shows blades that have been steeled on smooth knife steels, and there doesn't seem to be any flow or stretching there either.

I would think that we could conduct a test to see if this stretching effect really exists. If the leather stretches out the edge then a lot (say 500-1000 laps or so) of leather stropping on an already keen edge should produce a very delicate edge that would be too weak to withstand the stresses of shaving - sort of like a wire edge. If this doesn't happen then this effect either doesn't happen, or is so slight as to not really matter.

We could also conduct a test to see if the leather is abrasive. Take a shave-ready razor and dull it so that it no longer shaves, then see how many laps on a leather strop it takes to bring it back to shave-readiness.

I guess that I would ask this question.

How plastic is steel?

If steel has enough plastic properties, then when warmed could it not be stretched? Now I am talking nanometers. Such a small stretch that it would probably never register on any type of device, but enough of a stretch to lose some teeth and gain others.

Steel at razor levels of hardness isn't terribly plastic at all, and the temperatures needed to significantly increase plasticity will kill the temper. It's possible that a good stropping on leather might stretch out the the edge by a nanometer or so, but that's pretty insignificant at the scale we're talking about. Verhoeven measured a straight razor and commercial razor blade and found their edges varied between 0.35 and 0.45 microns across, or 350-450 nanometers. Because of the shallow edge angle the strop would have to stretch out the blade about 3 nanometers to achieve a 1 nanometer reduction in edge thickness.

If the leather strop stretched the edge to any significant amount, it seems likely that by now somebody would have noticed that leather stropping creates an overhoned edge.

Unfortunately Verhoeven only shows photos at 3000x, and not at 10,000x which was the magnification he used when he was measuring the edge thickness. At 10,000x you can see a *lot* of detail. Verhoeven was able to measure the edge thickness to the hundredth of a micron (10 nanometers) - small enough to see the effects of stretching even if the steel was only being stretched even a little bit. He doesn't mention any such effects, but that doesn't mean that they weren't there.

Ultimately it doesn't matter if steel stretches from stropping or not, what matters is if such an effect is substantial enough to matter. If the leather strop stretches the steel by 1 nanometer but the nightly corrosion eats away 100 nanometers then the stretching effect just doesn't matter at all.

The one variable in Verhoeven's study that I am curious about is stropping skill. Any of us that have been using a straight razor for any length of time realize that skill/ experience is an important factor. I read that he used one experienced straight razor user. But compared to what standard?

Did Verhoeven factor this "skill" into his research? Or is it possible that he overlooked, or maybe didn't even consider, that there is a difference between plain 'ole stropping and stropping with expertise? From what I've read in this thread, Verhoeven wasn't really all that interested in razors specifically. So possibly how the razor was stropped didn't really matter?

Another thing I question - where is the peer review of this study (or does this thread amount to that?) and where are the repeat studies? Rarely (actually never?) is it considered sufficient to base a theory on a single study.


Scott

Originally Posted by honedright

The one variable in Verhoeven's study that I am curious about is stropping skill. Any of us that have been using a straight razor for any length of time realize that skill/ experience is an important factor. I read that he used one experienced straight razor user. But compared to what standard?

Did Verhoeven factor this "skill" into his research? Or is it possible that he overlooked, or maybe didn't even consider, that there is a difference between plain 'ole stropping and stropping with expertise? From what I've read in this thread, Verhoeven wasn't really all that interested in razors specifically. So possibly how the razor was stropped didn't really matter?

I don't know. This is a problem with that part of the paper.

Originally Posted by honedright

Another thing I question - where is the peer review of this study (or does this thread amount to that?) and where are the repeat studies? Rarely (actually never?) is it considered sufficient to base a theory on a single study.

The Verhoeven paper wasn't published in a peer-reviewed journal, it was just a write-up of some experiments he did ,and if it was published at all it would have been as a Technical Note at ISU. So what peer review it's getting is from us and the woodworking guys, except that we don't have access to anything like the level of magnification he's using so we can't really attempt to replicate his experiments.

I think it's quite possible that he didn't strop correctly. He had jigs to hold his blades for honing and pasted stropping, and he probably used the same jigs and technique for plain leather stropping. Among other things this probably meant he didn't use any pressure when stropping on the bare leather, and it is possible this is why he didn't see the sorts of results he expected.

The basic problem we're facing is an epistemological one.

Just because nobody else in his position has repeated his experiments doesn't mean they're worthless and we can't base theories off of them. You can base theories off of anything or even nothing at all - what matters is their predictive value. The special theory of relativity, quantum chromodynamics, string theory were all used as working theories for years before anybody came up with specific experiments for them. These theories were used because they provided a workable explanation for the phenomena scientists were seeing, and that was sufficient. A theory doesn't even have to make sense, as long as it "works". If you get a chance, pick up a copy of Feynman's QED - the first chapter showcases this nicely (and is quite funny as well).

We do what we can with what we've got, which at the moment means the Verhoeven paper and the modern mechanics article. So we're right to be cautious interpreting the results, especially where his conclusions are at odds with common experience. But we are free to form theories from it, and indeed we should form theories from it. Testable, falsifiable theories.

Falsifiability was a concept a guy named Karl Popper came up with. Basically he explained that it isn't enough to test a theory to verify that it is true. It is easy to come up with a theory for which any result is true, the problem with such theories is that they aren't *useful* in a scientific sense, because they don't tell you what must not happen. Theories are not "true" or "false", they are merely more or less useful. Newton's theory of gravitation is useful not because it says the sorts of orbits that planets follow, but because it says that other types of orbits do not happen. Newton's theory has since been falsified - planets do follow orbits that are impossible under Newton's theories. But we still use his theories heavily even though they are wrong - we use them because they are still *useful* - though planetary orbits don't follow his predictions exactly they follow them closely enough for most purposes.

An example Popper gives of a non-falsifiable theory is Freud's theory of psychoanalysis, where psychological problems are due to earlier traumatic experiences though the patient may not actually remember them because his subconscious is suppressing these memories.

So for the theory that the leather strop draws out the blade, what sort of predictions does this theory make? What sort of things does it imply must happen if it is true, and what sorts of things must not happen if it is true? Similarly for all of our other honing and stropping theories.

At one time a popular theory was that the abrasives in the hone left "teeth" or serrations on the edge, and that the sharpest razors had the best teeth. There were all sorts of heated discussions about the best way to create the best teeth on the hone, and the best way to align them using the strop. But the key prediction was that the edge was toothed, which means that the theory would be proven false if honing did not produce such a serrated edge. Verhoeven's paper and the Modern Mechanics article both had photos of edges at a high enough magnification to see such teeth had they existed, and failed to observe them. So this is an example of a falsified theory in our area of interest.

What we need to do is formulate similarly falsifiable theories, and try to conduct some experiments to try and disprove (falsify) them.

I've done this myself for several theories, but more experiments are needed, and it would be nice if others would try to replicate my results.

Unpasted linen is a mild abrasive: If linen is abrasive, then a dull razor should get sharper given sufficient stropping on linen. If it does not sharpen then the theory is falsified. There's the question of "sufficient stropping", but this can be controlled somewhat by controlling the level of dullness in the razor. I conducted this experiment early last year, by taking a good-shaving wostenholm wedge, dulling it by cutting through cardboard until it would not shave arm hair, then stropping it on linen. The attempt at falsification failed - the razor returned to shaving sharp condition.

Unpasted leather is a mild abrasive: same as above, only with the leather side. I've tried this and was unable to significantly improve the sharpness of a dull razor. I consider this theory falsified.

Unpasted leather draws out the edge: I've already mentioned a potential experiment to falsify this theory - strop a shaving-sharp edge on bare leather and see if it develops a wire edge. If this effect is so slight that we're talking about a few nanometers, then the theory is unfalsifiable using our methods, which also means that even if it's true it's just not telling us anything useful. I haven't done this experiment yet, hopefully someone else will take this one up.

Unpasted leather does no more than align the edge: If this is true, then stropping a dull razor on leather should not provide any substantial improvement in sharpness, nor should stropping a sharp razor produce a wire edge.

Linen heats up the edge: not sure how to test this one without a pyrometer. But I'm uncertain how useful this theory is. For the edge to show the effects that are attributed to this heating it seems likely that the edge would have to get hot enough that it would also ruin the temper. Maybe some other more metallurgically-inclined member can devise a test that could falsify this theory.


Anybody got any others?

Here is a thought. May put this all to rest.

Serephim posted those lovely lapping film pics of his edges. One of them was darn near polished, no scratches.

Could Seraphim take a before shot of a polished edge and then a 20 strop, 40 strop, 60, strop, 80, strop, and 100 strop.

To see if the remaining scratches are removed, polished, or if more were added, abrasive.

It may take more laps than that. Remember we're talking about reversing a process that takes a week or two to dull an edge, during which time it has recieved a thousand or more laps on the leather... So the lap counts needed to falsify these theories may well be that high.

It's also important to start out with clean leather - crud and dust on the leather will affect the results. OTOH if a clean strop doesn't abrade, but a dirty one does abrade then that is useful knowledge - maybe it's the corrosion that comes off the razor and embeds in the leather that winds up providing the abrasive power - iron oxide is a popular abrasive in the form of red jewelers rouge, which would both falsify the original theory (untreated leather is abrasive) and provide us with a new theory (leather with iron oxide in it is abrasive).

I've tried to remove one source of variability from my own experiments by using a leather/linen paddle strop instead of a hanging strop. Given the high lap counts that are needed it's simply too easy to make a mistake at some point along the way, just because you get tired and this makes it easy to get careless. I got mine from Tony Miller, and I would recommend that anybody attempting to do these stropping experiments do the same.

At the moment I'm in the middle of what I anticipate will be a multi-year-long experiment to see if the sag in a hanging strop is important to the effectiveness of the strop and how it affects the lifetime of the edge, by using two different razors, stropping one with a horsehide/linen hanging strop and another with a horsehide/linen paddle strop.

Butting in long after thread ended...................

My belt of 10 years constant use has harness leather and plain forged steel buckle. I read this post while waiting for the wife to cook dinner and decided to see what the steel and leather was like in the areas of contact. Black leather and highly polished steel. Unless the fairies have come and polished the steel and scuffed their dirty boots on the leather, I can only conclude that leather is very mildly abrasive.
This in the context of stropping would show little abrasive effect in the short term but would in the long term. This is as long as you don't go back to the hone. Edges can and do improve with age (stropping).
I have been a carpenter/shipwright for 30 yrs and hand strop after I hone a blade and sometimes on a plain leather fixed to the top of my hone box. Stropping like this does remove the burr but not by abrasion but by breaking it off. A few light wipes back on the hone after get a better edge and better when followed on the CrO2 paddle.

up up and awaaaaay

PuFF