What's Your Opinion on this Stropping Article?

[duke762]

I picked this up at Coticule.be. A really nice write up on stropping but this has me puzzled. Is the author equating draw to strop efficiency?

Stropping lends its efficacy from friction. We'll discuss this in detail in the paragraph that addresses the stropping stroke, but the surface condition is a big contributing factor to the friction exerted on the edge. The amount of grip the leather has on steel determines how easily you can manage to get that friction going, while keeping pressure within reasonable range. If the leather is too slick, it'll require so much pressure that you might both deflect the strop and the blade. Strop deflection can be counteracted by pulling harder on the strop, but it'll remain awkward, and we have no solution for blade deflection. So far, I've always found the most agreeable draw on leather that had a slightly raised grain, typically found on Nubuck-like finishes. (I'm talking about the texture, not necessarily about the actual process).

I most certainly am not, using more pressure than needed to keep the spine on the strop and to control the blade.

Please note I'm only speaking of my experience with vintage shell strops.......

What this gentleman is saying seems to make some degree of sense, as he explains it. My theory would be that having the leather finished as flat as possible and smooth would be a better approach to getting more of the apex on the strop. I won't tolerate anything I can feel on my strop. Any raised grain is sanded off immediately. YMMV

I seem to never fail at finding something that contradicts something I thought I new.
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[Alum of Potash]

Russian leather comes to mind from the description. Or vegetable-tanned leather that has been sanded too give it some tooth. I think what you may be thinking of is pigskin instead.

On the pressure and friction, I don't have any explanations. All I can say is that over the past two months, and following the advice of a friend in France who made both the strop and razor, I have been using a small, felt-lined paddle strop with pasted sanded vegetable-tanned cowhide on one side and a kind of finished cowhide with a lot of draw on the other side. Because of the draw, it is necessary to apply a bit of pressure during the pass, one, to keep the blade moving, and two, to ensure that the edge is making contact with the leather, which is visibly apparent due to the slowed-down motion. With this, the strop count goes down, around 10 laps on the pasted side followed by around 10 laps on the plain leather side, again the surface area being that of a small paddle strop. This has been enough to keep my razor going thus far.

Oil-leather (wild juchten) is similar with regard to the draw of the paddle strop in question. In both cases, it really takes a firm hand and a controlled pass to tell the leather who's boss.

 

[Tony Miller]

Interesting observations but it brings up some questions:

A rough surface has some tooth and "should" thereby have more friction, but because it has some tooth there is less strop in contact with the edge so maybe less friction?

A glossy, polished surface strop should be slick and slippery with less friction, but because it is smooth it may have more surface contact with the edge and thereby more friction?

I know from my own experience a rough strop's friction greatly depends on how soft or firm the surface is. When I made a steerhide rough strop it had much more draw than a horsehide as the steer was softer and the "tooth" grabbed at the edge, where the firm horsehide 'tooth" sort of slides past it with less resistance. Both felt "rough" but the soft one clearly had more friction.

I have used smooth, slick leathers that almost stuck to the edge, others slipped past effortlessly. In materials other than strops and razors, true, rough surfaces would grip each other with lots of friction and smooth surfaces tend to slide more but once you reach a certain level of smooth many materials will 'wring" together and stick like they are glued.

While the article makes sense, I do feel there are more factors at play.

 

[Frank Shaves]

I do not understand the "physics" of stropping but what I do understand is that factors like the texture of the leather and the grind of the blade affect what you (as the stropper) need to do to get the blade humming on the leather - much like Ringo did on his hi-hat and John did on his rhythm guitar.