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

Originally Posted by Quick

Given the carbon (or stainless) steel we find in razor blades and a baseline at 70*F, at what temperature do you think the steel gets measurably more brittle? and at what temperature do you think it gets measurably softer?

I don't have any scientific data at hand. If zero degrees F won't do, lets say -10. I was having trouble straightening a sword one time. A bladesmith friend suggested heating to around 200F. That didnt make me a skilled straightener but it was easier to bend. 185-200_ish /215.

Originally Posted by Quick

Sure there is heat transfer but it is transfered from the metal that is hotter to the metal that is cooler. It's not instantaneous. You could heat the edge enough to change the rigidness of the edge without significantly heating the spine (at least for a little while). Try an electrical grinder. You can turn the edge glowing hot almost immediately and still touch the spine. The entire surface of the blade will act as a radiator. Some amount of heat could be completely dissapated/radiated before it ever reached the spine.

You make a good point. Even if there is heat generated due to friction between the edge and the canvas, the far greater mass of the spine will serve as a heat sink to immediately cool the edge back to where it started.

Originally Posted by Utopian

I checked the members google map.

The answer to your question is yes, there is a Fin, and he lives in Helsinki.

Thanks, you are always such a help!

Originally Posted by Joed

What was the question? Regardless of what you rub/strop your blade on it will heat up. Some materials will generate more heat than others. Remember carpet burn? Right after the carpet burn does your knee burn your hand? While there is heat generated, and maybe to some substantial amount, it is localized and it dissipates quickly ...

That's not damage from heat, it's mechanical debridement.

It's no more a 'burn' than what you would get if you took sandpaper to your knee and slowly ground off the skin. No heat, just abrasive... Just like stropping!

Originally Posted by joke1176

That's not damage from heat, it's mechanical debridement.

It's no more a 'burn' than what you would get if you took sandpaper to your knee and slowly ground off the skin. No heat, just abrasive... Just like stropping!

It's a bit of both. Take your hand and rub it back and forth quickly about 10 times on your bed sheets. This is not as course as a rug but will generate heat and warm your hand. Better yet, rub your hand on the rug lightly. Be careful not to rub hard enough to debride and skin. What do you feel?

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?

Originally Posted by Ben325e

I've read it too many times, folks. While we may continue to argue the merits of the canvas strop, let's get this one taken care of NOW. People say "strop a few times on the canvas strop to heat the edge, making it more malleable for the leather to do it's job"...... I think this is BS, too.

Consider what is being said: 20 or so laps on a canvas strop is enough to bring the temperature of the edge or the razor up high enough that it is actually more pliable for the leather component of your strop. What?!?! That's a load of codswollop.

Let's think of basic physics and heat transfer here: The area of contact between the razor and the strop is very small, especially in comparison to the entire surface area of the razor and tang. So, as you are swishing your razor along your strop, "building up heat", the entire rest of the razor and tang is being dragged through the air, causing a cooling effect. Try it. Right now. Raise your strop hand in the air, and swish it back and forth the speed and length of your typical strop stroke. Does it feel cooler or warmer than the hand that's not waving around? Unless you're waving your hand in front of a heater duct, it should feel cooler. If not, call your physician.

Part two: the heat does NOT stay at the edge. With the exception of the uber-cool Seraphim Seramix brand of razors, Straights are made out of metal. Metals conduct heat quite well in comparison to many other materials. So, when that little tiny edge or your razor picks up some heat due to friction, it shares it with it's neighbor. The heat would pass from the edge, through the grind, to the spine, along the tang, and end up in the monkey tail. (that sounds like top notch lyrics to a new kid's song.... from the edge spine through the grind to the spine along the tang and end up in the monkey tail... sing it... it's catchy!)

If you want to try a cool experiment regarding heat transfer, fill an empty gatorade bottle full of water. Put the cap on and go build a fire in your back yard. Throw the gatorade bottle into the hottest part of the fire. don't worry, it won't melt or burn. As the heat builds up in the plastic, it gets transferred to the water. The water continues to absorb the heat so effectively that the water will boil well before the plastic even thinks about melting. Try to consider how this same principle applies to straight razors and heat transfer away from the edge.

So, the heat would have to be great enough to not heat the edge, but the entire metal component of your razor, and then maintain a good bit of that heat while you drop the canvas and get the leather. And then we need to think, how many degrees does the temperature need to be raised to make any significant? Well, I for sure can't tell any noticeable difference in the temperature of my razor after using the canvas, so I can assume that it only needs to raise the temperature just a tiny bit. So, would it make more sense for me just to strop while in direct sunlight, or to raise the temp on my thermostat a bit? Would that make my razor sharper and smoother? No.

If you really want to heat the razor, then get out a 1200 watt hair dryer and blast the razor for a few minutes. it'll be hot, I promise. A lot more effective than a canvas strop. I still don't think it'll be hot enough to make a dang bit of difference in the sharpness of the razor.

Plus, when stropping, heat is a result of friction. I don't know about the rest of you folks, but I sense a heck of a lot more friction when stropping on latigo leather than I do on the canvas. So, if you wanted to heat the edge via stropping, leather makes much more sense than canvas.


I think when people say that the canvas "heats" or "warms" the edge or whatever, is just because they are regurgitating what they have read or heard. Don't believe everything you read or hear. If you do happen to be one of the folks who believes everything they read, then let me tell you... your straight razor edges will be MUCH better if you send Ben325e lots of money every month via Paypal. You gotta try it to believe it - it's truly phenomonal.

It's much more respectful and insightful to tell people the truth. If the canvas works for you (I use mine every time) but you don't know why, then say that. If you have a hypothesis, then say it is.

I would much rather someone say "I think that stropping with an X pattern is good because it smooths out the sides of the striations left by hone scratch patterns" than to hear them proclaim it like it is the truth. If you don't KNOW something, then don't say it like you do. There are many things that are still mysterious about straight razors, and it's okay if you don't know everything yet.

So, I'm in the "Canvas heats the edge" is BS camp. Where are you?

Ben, how about taking your canvas strop and razor outside of your house (leave the leather part inside). Strop your razor with the canvas letting the temperature of the razor equilibrate in between strokes (it should not take long as metal conducts heat well) and when you are done, resume your normal stropping routine with the leather indoors. If you get the same results, probably the increase of temperature is not the reason people use canvas. If you find that your shave sucks, perhaps there is something to it. By the way, there are many other ways to do this experiment, only this one is good because is winter time (around here, at least :-0 ).

Al raz.

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