General Question of Stropping and Honing my Dovo

unit said:
Can an edge be convexed on a bare leather strop (beyond the initial honing finish stropping)? Yes, but it will be done do at the cost of edge life and is the result of poor technique, not abrasives in my opinion.
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Are you saying an edge can be convexed but this is not the result of abrasive action? If so, then by what mechanism would it be accomplished? The presence of naturally occurring silicates found in the collagen and elastin of animal skin, and additional silicates added during the tanning process virtually assures a healthy dose of abrasives, tho likely very very small in particle size as many would have passed through cell membranes on their way to the skin/connective tissue. I'm open to the idea that plastic flow or deformation might be at work, but have found little to support this. I'm at a loss to explain the results so many get stropping on plain leather (myself included, tho I seldom use it), hard to believe it's a placebo effect.
 
HeavyHanded said:
Are you saying an edge can be convexed but this is not the result of abrasive action? If so, then by what mechanism would it be accomplished? The presence of naturally occurring silicates found in the collagen and elastin of animal skin, and additional silicates added during the tanning process virtually assures a healthy dose of abrasives, tho likely very very small in particle size as many would have passed through cell membranes on their way to the skin/connective tissue. I'm open to the idea that plastic flow or deformation might be at work, but have found little to support this. I'm at a loss to explain the results so many get stropping on plain leather (myself included, tho I seldom use it), hard to believe it's a placebo effect.
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I am not saying that there are not abrasives present in leather.

I am not saying that you could not perhaps use them over a long enough time to convex and edge. But suffice to say that time is going to be quite great and well over 10,000 laps on a strop.

I am saying that a razor gets dull in a time frame from normal use shaving and occasional misuse by accidental contact with something else in a time frame SIGNIFICANTLY shorter than the time frame necessary for any natural abrasives present in a decent leather strop to convex the edge.

But don't take my word for it, Google "Verhoeven sharpening" and take the time to review the volume of work he conducted and presented in his 2004 paper...or simply skip to the photos and conclusions.


I will say again (as I have said before) I can not answer the question as to what exactly is happening with a strop...but that should not negate an understanding of what is NOT happening. This is how science often works...we can not always explain what happens, but occasionally we can rule out processes through careful studies and experimentation.

can only speculate based on plausible explanations by others regarding what the mechanism is for a strop to refine an edge. I would SPECULATE without any PROOF that the strop removes contaminants and oxidation through burnishing, and re-aligns the edge that suffers slight distortion as it shaves hair.

Could I be wrong? Could all the guys I chat with off line that do this for a living be wrong? Could Verhoeven be wrong? ABSOLUTELY. But I think I would need some pretty compelling evidence beyond what I have seen presented so far...but I won't claim to have seen every study ever done...
 
unit said:
I am not saying that there are not abrasives present in leather.

I am not saying that you could not perhaps use them over a long enough time to convex and edge. But suffice to say that time is going to be quite great and well over 10,000 laps on a strop.

I am saying that a razor gets dull in a time frame from normal use shaving and occasional misuse by accidental contact with something else in a time frame SIGNIFICANTLY shorter than the time frame necessary for any natural abrasives present in a decent leather strop to convex the edge.

But don't take my word for it, Google "Verhoeven sharpening" and take the time to review the volume of work he conducted and presented in his 2004 paper...or simply skip to the photos and conclusions.


I will say again (as I have said before) I can not answer the question as to what exactly is happening with a strop...but that should not negate an understanding of what is NOT happening. This is how science often works...we can not always explain what happens, but occasionally we can rule out processes through careful studies and experimentation.

can only speculate based on plausible explanations by others regarding what the mechanism is for a strop to refine an edge. I would SPECULATE without any PROOF that the strop removes contaminants and oxidation through burnishing, and re-aligns the edge that suffers slight distortion as it shaves hair.

Could I be wrong? Could all the guys I chat with off line that do this for a living be wrong? Could Verhoeven be wrong? ABSOLUTELY. But I think I would need some pretty compelling evidence beyond what I have seen presented so far...but I won't claim to have seen every study ever done...
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I can't argue the bulk of your assertion and like you I don't really claim to know what is or isn't going on at the apex when stropping. I do know a couple of things though - Unlike Verhoeven I have seen under microscope traces of mineral or metallic debris that wasn't there prior to stropping - is this just garbage that escaped the blade cleaning, or residual burr formations being torn loose by connective tissue and not abrasion? I don't know. As to other materials convexing in shorter order, I have to agree as well - the level of silicates and abrasives in a host of natural and man-made items is likely far higher than most tanned leathers. But - having done enough reading about tanning methods I'd have to say there could easily be leathers out there with very high levels of abrasives, rivaling many papers and other plant-based surfaces such as linen. Based on the level of polish one can achieve just rubbing a piece of metal on a cut of leather, I would be astonished if it took anything close to 10,000 passes to make a profound change to the apex, for better or worse. This another one of those topics that will likely plod on unsettled for a long time.
 
HeavyHanded said:
Based on the level of polish one can achieve just rubbing a piece of metal on a cut of leather, I would be astonished if it took anything close to 10,000 passes to make a profound change to the apex, for better or worse. This another one of those topics that will likely plod on unsettled for a long time.
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You bring some good insight. (Thanks)

I agree that this will likely go unsettled for some time. I enjoy the ride though;)

When you mention rubbing a piece of metal on leather...are you considering mild metal or hardened blade steel at a hardness we would expect for a razor?

I would also speculate that the materials selected for professionally made premium razor strops will perform far differently than some of the things I see knife sharpeners use as strops. I hear people talk about making their own strops from hobby shop leather or old belts...these may well contain large silicates (and are perhaps enjoyed by knife sharpeners)?

There are a multitude of variables that could contribute to the confusion or varying observations.
 
The rub test I did was with (presumably) 1095 hardened to whatever Mora and Tops hardens their steel to - I believe its 56-58 for both. I basically gave the flat of the steel a rub with relatively light pressure on newspaper with ink, plain newspaper, and leather from an unused work belt. Possible it was only removing oxidation and that's what shined it up, but then it generally takes abrading action to remove oxidation as well...? The newspaper is remarkably abrasive. I recently made a "strop" by chopping a large electronics catalog down to about 1/2" along the spine - squeezed it in a clamp and used it as a strop along the cut edges of the sheet. I was trying to find out if there was something to the paper wheel setup independent of general conformity and speed. As a strop it worked very aggressively compared to using the face of a sheet of paper - which will shine up hardened steel very quickly in its own right. Removed several largish burrs and visibly brightened the entire edge - also made a huge difference in cutting ability. I've also cut pieces of belt leather up and found what looked like abrasive particles much larger than one could account for naturally, so either during the tanning process or when the belt was being cut (by me or at the factory) and tooled, it picked up a bunch or debris. The shape of the tissue fibers themselves are very good at catching and trapping debris too, so what Bluncut found and others have noticed makes sense whether the strop is abrading steel or simply tearing weakly held pieces free and accumulating them in the leather matrix - older strops are going to be more aggressive. And then, my microscope is optical, so I'm limited to items about 1u, whether they be abrasives or metal residue. There are streaks running through the leather that have a shine to them and this could easily be from silica deposits or just as easily be from oils or some other source. Many variables.
 
This is good as it had also occured to me for discussion within this topic someone should have examined our strops? Merely to see what is laying on their surface. Thus, allow us further information toward what is happening during stropping. Because, going over my stropped blades I'm seeing sharpening scratches close to removed, blades becoming shiny and blade emblems being removed. This is certainly more than straighten of the metal fins at its apex. Why Dr. Verhoeven didn't see this and state it in his paper makes me wonder. Yet, the guys in the other reference photographing hundreds of blades saw it and made comment on this. Agreed, a subject we will mull over for some time. DM
 
David Martin said:
Why Dr. Verhoeven didn't see this and state it in his paper makes me wonder
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I would suggest that there was probably great efforts to reduce or eliminate variables.

The average knife sharpener probably uses the same strop to remove burs as he/she does to strop blades. Those burrs may well become embedded in the strop and explain the scratches.

Or as pointed out previously, some leathers may have huge (relative) silicates resulting from processing. These would not be desired by many razor afis but loved by knife sharpeners (or those desiring micro convex).

The discrepancies between your observations, mine, and Verhoeven's may be easier to explain than we thought?
 
The other factor is that the fine-ness of a razor blade v. a knife edge can be shown by taking a shave-ready razor, and cutting paper with it. it could be that since Dr.Verhoeven was working primarily with knife geometry, the effects didn't present, but that they do with the angles involves with razors? If I had the time, and resources, I would love to re-create all of his experiments using everything from straights to axes, just to see what the variables are. Does hardness have anything to with it, and at what range? RC is a pretty loose scale, so could someone develop a more accurate scale? also a wear-resistance index? there are a lot of variables well outside of normal "scientific" range, which makes a lot of it more back of the envelope engineering than I think most people are looking for.
Its all cool stuff, Glad things have calmed down a bit.
 
I am not sure angles should have any impact. Regardless of if it is 16 inclusive or 30, you are still lapping a flat bevel against leather.

Rc seems pretty tight relative to the variance in hardness we see in blades. As far as I know razors are almost universally harder than knives (all else equal). Knife makers and users generally temper to reduce brittle/chipping. The razors I have tested were at a hardness of 63.

With regard to variables outside scientific range...that problem always plagues blades. Not least of which is the fact that the human element trumps all with use of free-hand guidance and the multitude of variables thrown at the apex during use. I eliminated the use and simply stropped an unused blade on a hanging barbers strop every day for a few hundred laps each day. It was clear to me that technique in stropping could lead to very different results...however, I feel that an acceptable assumption is that good technique is involved (after all, if you are incapable of properly stropping a razor to maintain the edge instead of damage it...why would you want to explore deeper into the science of a process you cannot utilize:))
 
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GG, Thats a good point about two different type blades used in the studies. Could be its much easier to see on one than the other. DM
 
In case it helps, this link to Verhoeven's technical report should work. Please let me know if it does not. Just now, I checked it using InternetExplorer, and it worked for me.
http://www-archive.mse.iastate.edu/...te.edu/static/files/verhoeven/KnifeShExps.pdf
Verhoeven discusses stropping and has electron microscope images starting around page 18.

There is also a thread in the WickedEdge forums, where Clay Allison is using an optical metallographic microscope to see the effects of stropping. You can find that thread here, with lots of pictures from Clay's microscope:
http://www.wickededgeusa.com/index....id=5&id=2399&limit=10&limitstart=90&Itemid=63

That thread is pretty long an involved, and I'm not sure I know all the parts of it. But in this section of that thread, Clay posts some images where he stropped on plain leather without any compound:
http://www.wickededgeusa.com/index....d=5&id=2399&limit=10&limitstart=140&Itemid=63

Finally, consider that in CATRA tests, the knife is used to cut silica impregnated paper until dull. Presumably, the silica is deliberately added as an abrasive to accelerate the test. So if silica is abrasive enough to _eventually_ dull a knife, then _in theory_ it has enough abrasiveness to affect the knife edge during stropping. But it seems, _in practice_, to have very little effect on the edge according to Verhoeven's tests, as well as initial tests by Clay Allison. And I suppose it maybe be possible that plain leather could help straighten out microscopic rolled edges and mis-alignments of the edge after damage from cutting. However, more testing would be a good thing, in my opinion.
http://www.bucorp.com/files/catra_test_results.pdf

Sincerely,
--Lagrangian
 
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In case it helps, this link to Verhoeven's technical report should work. Please let me know if it does not. Just now, I checked it using InternetExplorer, and it worked for me.
http://www-archive.mse.iastate.edu/f...nifeShExps.pdf
Verhoeven discusses stropping and has electron microscope images starting around page 18.
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What an excellent paper from one of the world's most respected institutions.

Stately stands my alma mater on the western plain. From her halls and to her glory, raise we now our strain. Gather now and sing her praises. Sing them loud and free. Come ye loyal sons and daughter. Hail to ISU.
 
I just toss out ideas, I never claim they are good!;) :D

What I was meaning by the tolerance of the hardness scale, its a pretty big scale, with wide increments, if there was a consistent way to judge the hardness of a material in a much more detailed, fine grained way, then more could be learned.
As for stropping, I seem to be good at it, but if I don't actually know what I'm doing, maybe I'm only good by accident, or as a byproduct of something else?
 
gadgetgeek said:
As for stropping, I seem to be good at it, but if I don't actually know what I'm doing, maybe I'm only good by accident, or as a byproduct of something else?
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Perhaps it is a byproduct...but I am not sure that a person really needs to understand a process to be able to do it well and achieve the desired results. There are number of examples...I have no idea what is actually happening inside the box as I type this...but I am able to convey the message to you;)

I think "stropping" is a pretty variable process in that there are a number of people out there "stropping" with different techniques and mediums. Honestly, I am not even sure that what (perhaps) 99% of the people on this forum do with their blades and strops is actually stropping. If there are abrasives loaded onto the carrier, isn't the proper term "lapping"? I could be wrong...but my point is, if you are lapping your blade on a piece of leather loaded with 6 micron diamonds (or even chromium oxide, for that matter), you are almost certainly achieving something very different than what the person using a strop of bare premium horse hide.

In the bigger picture, it is all about the results...so the process is immaterial. But as thinking scientific types, it is fun to ponder WTH is actually going on.
 
gadgetgeek said:
Before we derail the gentleman's tread, any talk of what is happening when stropping on bare leather is conjecture. Until someone gets large scanning electron microscope photos of a razor before, during, and after stropping, we are just guessing. The "fin" theory comes from old manufacturers instructions. Those instructions advocated owning several razors to rotate. I wonder why? (not that they would....lie)
There are as many methods as there are shavers, do what makes you happy.
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If you shave every day, after about a couple of weeks your razor's edge will feel dull and lifeless and will cease to sing off the strop. Stropping will seem & feel ineffective and the razor will seem to get continuously blunter. If your razor can rest for the 48 hours (if you have 2 razors and rotate them) the spring/hardness seems to come back. I don't really know why this is, but I have noted it myself. Even if you shave every other day and only have one straight razor, you will notice this (kind of cumulative) effect after about a month or two. The temptation, then, is to hone the blade because the razor feels blunt. Then eventually you'll notice that the length of time between honings becomes shorter and shorter as well. I can think of no scientific or metallurgical explanation for this effect and there may be a degree of auto-suggestion involved, but rotating blades does seem to work (for me anyway)

PS: I strop dry and always have.
 
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