vgeorge said:
Why does a coticule edge particularly benefit more from the linen stropping? (Is that really true, or urban legend?)
A valid question. I have always said that a freshly honed Coticule edge requires extra efforts on a linen strop. I didn't mean that as a direct comparison against other hones, but as compared to what most guys find a sufficiant amount of laps for "upkeep" stropping in between shaves. The freshly honed edge require
more linen than the edge already in use. I noticed that some have made of it that I said that a Coticule edge requirs more linen than any other hone. I think that is an overly simplified interpretation. I do think however, that the finer the abrasives used for the finishing stage, the less linen stropping is needed. Chromium Oxide, for instance, does not require any linen stropping prior to leather (as long as you make sure not to transfer any CrO to the surface of the leather). I would also suspect that a Shapton 30K would not demand much linen, if any. But I don't know that for fact, because I don't own this hone. I do own a Chosera 10K, that one does require linen stropping in my experience, but less than a Coticule finished edge.
While sharpening, particles harder than steel plow throught the bevel. They remove part of the grooves they're drawing, but they also displace the sides of those grooves, without actually removing the steel. Part of the action is a buffing one, were the surface of the steel is more malled and plastered into shape, rather than purely abraded. I think that hones with particle hardness around 7.5 Mohs (Coticules) have a different abrasion/buffing ratio than hones with a particle hardness of 9 Mohs and more.
Furhtermore, on a polished steel surface, there is something called the Beilby layer. On a thoroughly worked surface, that layer extents 0.1 micron deep into the surface. If we know that that a cutting bevel consists of 2 sides that meet at a radius of approximately 0.4 micron, then 0.2 microns of that radius being "Beilby-fied", this becomes a very important factor in the behavior of the very edge. Some very interesting literature can be found here:
http://webpages.dcu.ie/~stokesjt/ThermalSpraying/Book/Chapter1.pdf
This paper does not deal with sharpening directly, but several of the discussed principles certainly come together at the very edge of a razor, where the steel, due to it's thinness must be considered more "surface" than "core".
How the hone reformulates the steel structure, will certainly have an influence in what strops can do afterwards.
vgeorge said:
In your judgment, are the plastic flows on the edge aided by leather stropping happen from just physical forces (rubbing action), or temperature changes from the friction (between leather and steel edge)?
Thanks.
I don't really know. We're dealing with processes at moleculary level here. Heat is essentially molecules loaded with kinetic energy. Molecules dance around eachother and the hotter they get, the more energetic they dance. Hence it's a form of movement. If we're going to force movement of molecules by rubbing with something that has enough friction, heat will be the result of that process. But not its cause, I would say.
Kind regards,
Bart.
