Thread: Verhoeven Paper Question

Originally Posted by mparker762

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.

Since you've mentioned the teeth issue, I'll use this opportunity to bring up a question I asked long ago in another thread here: http://straightrazorpalace.com/razor...ess-steel.html

In post #25 there is a 500X photograph of a razors edge. It seems to show a serrated edge, or teeth. I asked Seraphim if he thought that the teeth were just an artifact of lighting since, supposedly, teeth do not really exist as mentioned above in the quote. Seraphim responded that he thought the teeth (serrations) were there, and not a result of lighting.

So I'm wondering is Seraphim's photo a fluke, or does his photo actually reveal a serrated razors edge and did Verhoeven and Modern Mechanics falsely falsify the teeth theory.


Scott

Originally Posted by singlewedge

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.

You really should all read the following document.
http://webpages.dcu.ie/~stokesjt/The...k/Chapter1.pdf

It explains how the surface of hardened steel consists out of different layers. I don't think there's much research done to how these layers behave at the edge of a finely hone razor.
While on a structural level, hardened steel has little plasticity, this is not entirely true for plasticity at surface level, where honing and stropping forces can be extreme on a molecular scale.
At the very edge, "surface level" meets "structural level", which opens unexpected possibilities. The fact that the distal edge is bendable may be partial to that, and it certainly suggests ductility on that level.

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.

The fact that it takes "special" skill is proof that there's more going on than abrasion. Abrasion takes no skill: you simply rub two things together. If significant abrasion occurs, magnifying to 3000X with good optical resolution (SEM) will reveal it.
If stropping requires, for instance, "speed", it surely points to other processes than mere abrasion. The question remains, what is the nature of those other processes?

Bart.

Originally Posted by mparker762

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





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?

That, sir, is a mighty fine post.

In answer to your final question, I think that heat though friction can be very significant on an microscopically shallow surface level, while it dissipates too fast into the body of the steel to really affect the metallurgical state of the steel.
Similar things happen with pressure. I'd like to quote a sentence out of the document I linked in my previous post. ("asperities" are bumps and pits that form the microscopical texture of steel)
"(3) Adhesive Wear
Adhesive wear is often called galling or scuffing, where interfacial adhesive junctions lock together as two surfaces slide across each other under pressure, according to Bhushan and Gupta (1991). As normal pressure is applied, local pressure at the
asperities become extremely high. Often the yield stress is exceeded, and the asperities deform plastically until the real area of contact has increased sufficiently to support the applied load."

I would also like to speculate that these principles, whatever they are, do affect the hardness and sturdiness of the steel. After all, the stropping effect needs to be reapplied each shave.

Bart.

Originally Posted by honedright

Since you've mentioned the teeth issue, I'll use this opportunity to bring up a question I asked long ago in another thread here: http://straightrazorpalace.com/razor...ess-steel.html

In post #25 there is a 500X photograph of a razors edge. It seems to show a serrated edge, or teeth. I asked Seraphim if he thought that the teeth were just an artifact of lighting since, supposedly, teeth do not really exist as mentioned above in the quote. Seraphim responded that he thought the teeth (serrations) were there, and not a result of lighting.

So I'm wondering is Seraphim's photo a fluke, or does his photo actually reveal a serrated razors edge and did Verhoeven and Modern Mechanics miss something?


Scott

The Modern Mechanics method of optical magnification might very well have lacked optical resolution to show any teeth. Verhoeven's scanning electron microscope is capable of much better resolution than any optical device, so his pictures are beyond suspicion.
They show us that micro-serrations are not per definition present, which is counterintuitive, because one would expect that any scratch pattern running perpendicular to the edge would end up in a sawtooth pattern, regardless how fine the hone. These pictures show us, that such expectations are not necessarily true for finely honed edges. But they don't rule out the possibility of it. Every one who's ever been HHT-ing, knows that coarsely honed edges perform rather well on that test. That is due to the sawteeth at the edge. They concentrate the weight of the hair on a few spikes of the edge, raising the local PSI till those few spikes penetrate the outer layer of the hair shaft. Those edges also grab skin better, as can clearly be felt at the TPT. As soon you remove the sawteeth with a finer hone, this HHT-ability dissappears, only to emerge again when the edge becomes keener and a new teeth pattern at higher frequency has formed. In the end, the razor has no teeth pattern and needs to be extremely keen to sever the hair. I personally believe this will yield the smoothest shave, but it is not ruled out that you couldn't shave with a micro-serrated edge, only that is is not needed per se, and that they're often not found on edges that shave very well.

Bart.

Originally Posted by Bart

The Modern Mechanics method of optical magnification might very well have lacked optical resolution to show any teeth. Verhoeven's scanning electron microscope is capable of much better resolution than any optical device, so his pictures are beyond suspicion.
They show us that micro-serrations are not per definition present, which is counterintuitive, because one would expect that any scratch pattern running perpendicular to the edge would end up in a sawtooth pattern, regardless how fine the hone. These pictures show us, that such expectations are not necessarily true for finely honed edges. But they don't rule out the possibility of it. Every one who's ever been HHT-ing, knows that coarsely honed edges perform rather well on that test. That is due to the sawteeth at the edge. They concentrate the weight of the hair on a few spikes of the edge, raising the local PSI till those few spikes penetrate the outer layer of the hair shaft. Those edges also grab skin better, as can clearly be felt at the TPT. As soon you remove the sawteeth with a finer hone, this HHT-ability dissappears, only to emerge again when the edge becomes keener and a new teeth pattern at higher frequency has formed. In the end, the razor has no teeth pattern and needs to be extremely keen to sever the hair. I personally believe this will yield the smoothest shave, but it is not ruled out that you couldn't shave with a micro-serrated edge, only that is is not needed per se, and that they're often not found on edges that shave very well.

Bart.

Per Seraphim's Dovo review thread, the 500x photo revealing a serrated edge is of a "smooth" shaving razor.

Without going back and reading Verhoeven's work, did anyone actually shave with the razors he photographed? And if so, what was the quality?


Scott

Originally Posted by honedright

Per Seraphim's Dovo review thread, the 500x photo revealing a serrated edge is of a "smooth" shaving razor.

I'm certainly not disputing that.

Originally Posted by honedright

Without going back and reading Verhoeven's work, did anyone actually shave with the razors he photographed? And if so, what was the quality?

Verhoeven only photographed one razor, owned, honed and stropped by one Mr. William Dauksch that had "several decades" straight razor experience. He compared the edges to commercial Gillette blades and found them "close" to those standards, although a litlle bit rougher at extremely high magnification, of which he published no pictures. He did publish 800X pictures that shows a very straight and undisturbed edge.
The experiments he did on water hones and leather were all conducted with standard stainless steel razor blades, that were put in a fixture for consistent honing angle. He compared images and measured the final width of the bevel tip. He doesn't report any shaving tests with those blades. I think it's safe to assume that he probably considered such shave tests far too subjective and influenced by other factors, to base scientific conclusions upon.

In commercial blades, Verhoeven found: "Edge widths of 0.3 to 0.5 microns, edge straightness of essentially straight line quality, little to no edge roughness as viewed from the side, and a very good face smoothness."

Bart.

Originally Posted by mparker762

The Verhoeven paper wasn't published in a peer-reviewed journal...

His peers would be another Engineer with experience and/or training in Metallurgy/Materials sciences. The vast majority of us, if any, are not one of his peers.

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

Agreed. Until we all agree on a set of test parameters and methods, it is much more philosophy then engineering. Even after that, it's easy to pick apart any study in detail.

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.
...

Sure, linen heats it up; but probably not to any significant effect. I have a digital multimeter w an infrared temperature probe that could easily measure before and after temps on a stropped edge. Mine is laboratory grade; but I saw one at Lowe's for less than $50, which should be good enough to prove the hypothesis. But as long as my strop is giving me practical results, I don't really care what the "stropping temperature" is. The last thing I want to do is turn an enjoyable hobby into another "Engineering job".

However, about 8-10 months ago I did hold a razor to my cheek before and after around 80 fast laps on leather. I was curious after reading one of the many posts about the subject. I was certain that the temperature went up slightly, but not curious/dedicated enough to break out the meter to get hard figures.

Originally Posted by honedright

...
So I'm wondering is Seraphim's photo a fluke, or does his photo actually reveal a serrated razors edge and did Verhoeven and Modern Mechanics falsely falsify the teeth theory.
...

Maybe, maybe not. It's certainly another theory to investigate for anyone that has the interest and access to the necessary equipment.

Actually Verhoeven's photos do show teeth, but only when honed with fairly coarse grit hones. As the hones got finer and the size of the scratches became comparable to the thickness of the edge then the teeth disappeared.

AFAIK nobody shaved with his edges. But he also included high-magnification photos of commercial razor blades. No teeth. With his own edges he shows progressions of grits, and you can see the transformation of the edge honed at knife-type grits up through 8000k waterstones, then diamond and chrome oxide pastes, losing their teeth in the process but becoming extremely sharp.

I'm generally extremely cautious at interpreting amateur optical shots, because flat shiny surfaces are intrinsically difficult to photograph due to the extreme contrasts, the lighting can be extremely tricky to manage, and slight differences in the intensity and direction of the light can produce wildly different photos. Electron microscopes are much better at this sort of thing, both by the nature of the scope, and because of the training of the operators.

I haven't read the linked article yet. I'm aware of adhesive effects between two metals, but thought it was only really an issue between polished surfaces of similar materials - does it say that adhesive wear is possible between wildly dissimilar materials, like leather and steel? And is the effect large enough to be significant for our purposes? If it happens but isn't enough to keep a razor sharp then why do we care?

This is (I believe) the purpose of our inquiry in this thread - what services do the two sides of strop really perform, and how can we use this to improve the strop's utility for maintaining the razor? Whether the leather side of the strop is abrasive, or plastically deforms the steel edge, how significant is this at maintaining the edge, and how can we use this information?

I think the first step should be some specific tests to explore what effects are occurring at a scale that interests us. How much abrasion is the leather capable of, how much plastic deformation occurs and what type of deformation (straightening the edge vs drawing out the edge), etc. This isn't as much fun as arguing about it here, but pure discussion isn't as likely to give us answers as actually going out and doing some experiments.

Originally Posted by mparker762

I think the first step should be some specific tests to explore what effects are occurring at a scale that interests us. How much abrasion is the leather capable of, how much plastic deformation occurs and what type of deformation (straightening the edge vs drawing out the edge), etc. This isn't as much fun as arguing about it here, but pure discussion isn't as likely to give us answers as actually going out and doing some experiments.

Agreed. I think we came as far as possible in rounding up a good status questionis on this topic. It's unlikely to find any published experiments that offer direct insight on steel behavior to stropping, since it's a technique that doesn't seem to have any industrial use. I've done a lot of internet search on that in the past months.
But I also don't think we'd be able to make any progress without access to advanced methods of probing the resulting edges after experiments. Access to some form of Electron microscopy seems imperative. I might have one shot at gaining access to such a device for one or two evenings, but I have to talk to a friend about that first, 'cause he needs to pull the favors on my behalf. Even if it would happen, I'm not even sure what kind of experiments to set up.
I believe Seraphim has regular access to a SEM, maybe he's willing to conduct some field tests.

Bart.

Hopefully we can devise tests that we can do with just a strop and razor, using our face as the test instrument - these are the conditions in which we hope to make use of this information, after all. The electron microscope can confirm our results, and provide an explanation for what we're detecting, but I'm not sure it should be the primary test. For one, it means that our results can't be replicated by J. Random Shaver who doesn't have access to such equipment, and secondly I think it also keeps us focused on improving the shave instead of drifting off into areas of theoretical interest.