Thread: Canvas "heats" the edge: Fact or Fiction?

No doubt heat is produced when you overcome friction with mechanical force. In this case it's how much. We're looking for enough heat to make carbon/stainless steel softer. Soft enough to make a measurable difference with the light forces applied when stropping.

I suppose one might speculate that extreme heat is generated in only a few microns worth of edge. Even if this occured it would have dissapated long before you could move a blade from the canvas to the leather.

Originally Posted by Quick

No doubt heat is produced when you overcome friction with mechanical force. In this case it's how much. We're looking for enough heat to make carbon/stainless steel softer. Soft enough to make a measurable difference with the light forces applied when stropping.

I suppose one might speculate that extreme heat is generated in only a few microns worth of edge. Even if this occured it would have dissapated long before you could move a blade from the canvas to the leather.

I mostly agree. Most heat generated would be dissipated going from the canvas to the leather. Also I agree that only a few 'microns' of the edge MAY be heated substantially. This happens on both the canvas AND the leather. With the cross section of the edge being stropped even the briefest time spent at an elevated temperature would effect the metallurgy at the edge introducing and/or releasing stress. How much of the edge needs to be heated to effect the shave? Not much. A few 'microns' may do it. Since there is speculation as to the amount of metal being heated to any appreciable amount we should focus on what we know. 1) The canvas is slightly abrasive 2) Heat is generated by mechanically overcoming friction 3) Heat can be generated on the canvas or the leather 4) Only a very small cross section or the edge needs to be altered to effect the edge and shave 5) Increasing the temperature of metal to ~ 400- 450 f effects metallurgy and releases metal stress 6) The sounds generated stropping on canvas are different than stropping on leather.

Does the canvas do any of these things better than the leather? I'm not sure better, but maybe faster. Does stropping on canvas cause any effects on the metal that leather doesn't? We would have to measure each part using both materials to be sure. We would also need to evaluate if any events caused by each process have been missed. What is happening to the metal stropped on canvas that makes the sound different than on leather. That may be the key. From the limited observations I can make during normal stropping I can say for sure that after honing I can achieve a smoother/sharper edge faster using the canvas than if I just used the leather. As much as I enjoy honing and sharpening my straights I don't believe you will ever see me honing out bug bites in the edge using an 8k hone. At least not in this life time. If anyone enjoys stropping on leather and prefer not to use the canvas that's their call. I'm sure an edge that meets their desires can be achieved. I'm not being judgmental here. To me stropping is a means to an end and I enjoy the shave much more that I do stropping so I use the canvas.

Here's curve: Does the mechanical motion of stropping on canvas generate any electrical by product that would effect the metal bonds on the edge at a microscopic level?

I agree with everything you say above. But to the subject of the thread, I don't believe it's possible to "soften" the metal (due to the heat generated) by stropping on canvas first in order to make subsequent stropping on leather more effective.

Here's a thought: I believe this thread opened (I'm too lazy to go back and read the first post) with the idea that barbers stropped first on the canvas side to heat the razor blade and prepping the blade for the leather strop.

Now, has anyone any idea just how "hot" those barbers might have meant? Could it be that they just meant to get a cold steel blade, after sitting in a drawer all night, up to room temp? Remember that barbers were mostly stuck behind their chairs, and hot running water was not that common at the time. The "canvas strop heating the blade theory" probably came about around that time period. Maybe that's all that was meant and intended. Would stropping a cold blade warm it up some?

And, does a room temp (76 deg) blade strop better than a cold (say a shop in the mid-west, dead of winter or something like that) razor blade?

S.C. Thorpe says, in his Standard Text of Barbering that in the case of honing, both the razor and the hone should be at room temp for best results. Could it be the same for stropping?

Just a thought to add to the debate.



Scott

Friction causes heat. The more friction the more heat. We strop lightly because we do not want the cutting edge to crumble or curl upwards.

Steel conducts heat fast. When stropping at the speed the more experienced stroppers strop the air flowing above the heated bevel will blow the heat away.

So the little heat generated by stropping at light pressure will be blown and conducted away from the cutting edge resulting in negligeable increase of temperature.

Has anyone ever taken infra-red pictures of a razor being stropped?

OK, here's my latest:

Canvas is there as a base for applying pastes etc to, which is something you can't do with your regular stropping surface.

In the barbers' manuals of olden times they say to prepare the canvas by rubbing in a white soap to fill in the voids. I myself rubbed in Dovo white to fill the voids. Before adding the white, the canvas was of little discernable value.

So, the canvas isn't helpful by heating the edge, nor by simple canvas friction, but rather as a foundation upon which to apply a fine medium.

Canvas/Linen strops were and are for sharpening the edge and as Seraphim points out, the canvas/linen also makes a great foundation for pastes. I very much doubt that the Linen was EVER referred to for "heating" the razors edge. I am a firm believer in the beneficial use of the Linen in preparing a razor for shaving but not in the dreamt up ways some on here in the past have said it works. There is a lot of false information passed about on this forum as if it is fact. A compilation of FACTS should be added to the database for newcomers to access. eg. Fin etc If something works well and needs no improvement....why analize it then try to reinvent it, which seems to happen.

I vote: Cut out the BS.

PuFF

I nominate Ben325e as head SRP MythBuster.

Here's the link for canvas strops of yore...

Originally Posted by PuFFaH

I very much doubt that the Linen was EVER referred to for "heating" the razors edge.
PuFF

Here it is: A.B. Moler, The Barbers' Manual 1911, revised edition 1926 p.38

"There is a friction in stropping on the canvas that heats the metal, thereby expanding it and bringing it out to a keener edge so enough stropping should be given on the canvas to heat the blade, from one-half to one dozen strokes."

In 1893 A.B. Moler established the first professional college for barbers in the United States.


Scott