Thread: Verhoeven Paper Question

Originally Posted by Chris L

It's been about a year and a half since I read the article. Did he conclude that plain unpasted wool felt (animal hair) actually sharpened the steel but leather, animal hide did not? Would your suspicion regarding cotton or linen plant fibers having steel sharpening potential be unpasted plain "linen" or pasted with something? That would seem odd to me that a plain unpasted plant fiber or animal hair could sharpen steel but leather could not.

Yes, plain hard felt did sharpen the edge - this could be clearly seen under the microscope. He was stropping with the blade slightly inclined, so the felt produced a secondary bevel, but presumably had he not elevated the blade it would have slightly abraded the entire bevel. My belief is that the linen strop acts similarly, though I don't *know* this for a fact. I did an experiment once where I intentionally dulled a razor with cardboard, then brought it back to shaving condition by stropping on the linen. Either the strop is "drawing out" the steel or it's abrading the metal away. Verhoeven didn't find any "drawing out" effect in any of his stropping test (pasted, leather, or felt), so I'm inclined to believe abrasion is the most likely explanation. I don't know why hair/plant fibers are abrasive while leather isn't, that's just what he found.

Verhoeve was actually looking at leather to investigate the belief that leather stropping breaks off the burr caused by overhoning. This is how chisel and knife sharpeners tend to sharpen things - they sharpen till a burr is formed, then strop it off. But Verhoeven found that leather didn't even remove the burr, much less remove any steel along the bevel. But the felt strop did remove the burr and abraded the metal along the edge. There was a distinct difference in the abrasion patterns caused by the felt vs the pasted leather - the felt seemed to leave a rougher abrasion pattern, but IIRC it was a slower abrasive than the 0.5 chrome oxide (from what I recall from looking at his secondary bevels after similar # of laps).

Originally Posted by mparker762

Yes, plain hard felt did sharpen the edge - this could be clearly seen under the microscope. He was stropping with the blade slightly inclined, so the felt produced a secondary bevel, but presumably had he not elevated the blade it would have slightly abraded the entire bevel. My belief is that the linen strop acts similarly, though I don't *know* this for a fact. I did an experiment once where I intentionally dulled a razor with cardboard, then brought it back to shaving condition by stropping on the linen. Either the strop is "drawing out" the steel or it's abrading the metal away. Verhoeven didn't find any "drawing out" effect in any of his stropping test (pasted, leather, or felt), so I'm inclined to believe abrasion is the most likely explanation. I don't know why hair/plant fibers are abrasive while leather isn't, that's just what he found.

Verhoeve was actually looking at leather to investigate the belief that leather stropping breaks off the burr caused by overhoning. This is how chisel and knife sharpeners tend to sharpen things - they sharpen till a burr is formed, then strop it off. But Verhoeven found that leather didn't even remove the burr, much less remove any steel along the bevel. But the felt strop did remove the burr and abraded the metal along the edge. There was a distinct difference in the abrasion patterns caused by the felt vs the pasted leather - the felt seemed to leave a rougher abrasion pattern, but IIRC it was a slower abrasive than the 0.5 chrome oxide (from what I recall from looking at his secondary bevels after similar # of laps).

Could you point me to the phrases where Verhoeven talks about stropping on felt (other than on felt wheels loaded with abrasive compound), and to the parts where he compares felt to leather loaded with abrasives?
Could you also point me to the phrases where Verhoeven tested the "drawing out" effect and found nothing?

It seems that we are reading different documents, or at least a different version. The one I thought we were discussing is here:
http://www.bushcraftuk.com/downloads...nifeshexps.pdf
and also here (same document):
http://mse.iastate.edu/fileadmin/www...nifeShExps.pdf

Thank you,
Bart.

Here's the man:
John Verhoeven

and his reputation.

Did Mr. V publish info on the edge dimension after leather stropping, or as i recall he only observed the scratch pattern to be little changed. while abrasive strops were more instantaneous.

The point as he states was to discover the best way to remove the "bur" ;matching the straight razor standard .3 micron edge was the best one could look for. (except for John J's .1 micron steeled folded bur) For our purposes his best solution would be 6k to pasted strop.

He didn't post the edge dimension. But if the strop couldn't even straighten out the burrs it's unlikely to have drawn out the thicker bevel.

I couldn't help but giggle when I read that a plain leather strop couldn't remove a burr.

This will come as a big (and humorous) surprise to hundreds of woodcarvers and knife sharpeners who do it every day. I have personally done it dozens, or hundreds, of times with woodworking tools and knives. It is faster on a pasted strop, but still works on a plain one. If Verhoeven couldn't do it then he needs a better technique, a much smaller burr, or maybe some different leather. This is a neat example of an instance where a scientific study is directly at odds with the practical experience of many craftsmen.

The stropping-on-plain-leather experiment was done in two different parts of the test (honing and tormek) in two different conditions (lab and a workshop) by two different people (Verhoeven and Pendry), and had the same results. Verhoeven also tested both hard and soft leather and saw no real difference.

These two leather tests were repeated with chrome oxide pasting and they observed the sorts of improvements that we ourselves see. So I'm at a loss as to what they could have been doing wrong on the plain-leather test that they did right on the pasted leather test, and am inclined to believe that leather just isn't abrasive, and all it really does is shove the edge back into alignment.

Now he did use a hard backing for his leather strops, so the lack of sag may have made a difference since there would have been less pressure on the edge. But thats how the woodworkers strop their chisels, and they claim their bench strops do make a difference. It may be that they use more pressure than Verhoeven did.

I've never really seen the leather act like an abrasive - it can improve an edge a bit after it comes off the hone or linen, but you hit its limit really fast, within 30 laps or so. I've tried doing hundreds of laps on the leather to see if it will improve further and haven't seen it. But the linen side does seem to behave more like you'd expect a hone to act - you can keep stropping a dullish razor and it will keep getting sharper, and as you go on and use less pressure you get more sharpness. My one serious test of this involved trying to sharpen a dull razor using only the linen. It took around a 1500 laps* but the blade improved over the course of this stropping session until it finally came back to shave-readiness.

*I don't think it really should have taken that many laps, but I made a mistake. I started on a new Illinois strop with that plasticky linen, and it seemed to get the razor decently sharp within about 400 laps, but the edge was still rough, so I kept going and at the 800 lap point it was still rough so I kept going and when it was unchanged at the 1200 lap mark I switched to my Craftsman strop, and that got it smooth and sharp in a few hundred more laps. I suspect that 3-400 laps on the Craftsman would have done the trick. I know that sounds like a lot, but it's maybe 10 minutes worth of work. Also, after the 800 lap mark I did 500 laps on plain leather to see if that would smooth out the edge and didn't see any real improvement. So the razor really had about 2000 laps on it in the course of the evening: 800 Illinois linen (sharp but rough), then 500 Illinois leather (did nothing), then 400 Illinois linen (did nothing), 200 Craftsman linen (sharp and smooth), 100 Craftsman leather (sharper and smoother). And yes my arm was really really tired by the end of it.

Originally Posted by Bart

Could you point me to the phrases where Verhoeven talks about stropping on felt (other than on felt wheels loaded with abrasive compound), and to the parts where he compares felt to leather loaded with abrasives?
Could you also point me to the phrases where Verhoeven tested the "drawing out" effect and found nothing?

It seems that we are reading different documents, or at least a different version. The one I thought we were discussing is here:
http://www.bushcraftuk.com/downloads...nifeshexps.pdf
and also here (same document):
http://mse.iastate.edu/fileadmin/www...nifeShExps.pdf

Thank you,
Bart.

Hmm, we're talking about the same document. I just went back through it searching for "felt" and it appears that I was mistaken and he used the white bar on the felt and cloth in all experiments.

BTW I've used the white bar on my linen strops with success. It's a submicron tin oxide (some variant of Linde polish) and it works just fine. Just rub it on like a crayon. It seems to act like the Dovo white paste, and it wouldn't surprise me to discover that the Dovo stuff is just repackaged Linde paste. The white stick is available at any decent-sized hardware store for about $3, and it won't leave green stains like chrome oxide.

Verhoeven never specifically talked about any "drawing out" effect. But it doesn't show up in any of his photos, and he never mentions such a thing in the article that I recall (though I'm beginning to suspect my recollection). He did mention that the leather strop scratched the blades some (possibly dust on the leather), but otherwise had no effect.