BlueDun said:
I know about a study of the University in Liège (which is the nearest big city to the Coticule region). I also own a copy of "Ardoise et Coticul en Terre de Salm", published in 2007 by the Geological Survey of Belgium (a subdivision of the Royal Science Institute). The book (in French) offers a multidisciplinary approach. Also the Belgischer Brocken website seems to agree that Coticules and BBW's both rely on spessartine garnets. I think "garnet" and "grenade" is the same. I'm no geologist, but if I understand any of it, spessartine garnets can vary both in size and color greatly.
Here's a quote from
[note=Belgischer-Brocken]Untersuchung einiger einzelnen Granaten im REM hat uns gezeigt, dass es sich um reine Mangan-Granate handelt, den sogenannten Spessartin. Chemisch-Mineralogisch ist der Granat eine Mischkristallrreihe mit verschiedenen Gehalten an Mg, Fe, Mn, Al und Ca. Der Spessartin ist ein Endglied der Mischkristallreihe und besteht neben SiO4 auschließlich aus Mangan und Aluminium. Die Elemtanalyse eines Granaten im belgischen Brocken Gelb zeigt das mitgeschickte Bild „Analyse“, die Vorherrschaft von Si, O, Mn, Al mit Spuren von Ca ist gut erkennbar. Vorkommen von reinen Spessartinen sind relativ selten, da fast immer Mischkristalle vorliegen. Sie können aber die Granate im BB mit ruhigen Gewissen als „Spessartin“ definieren bzw. bezeichnen.[/note]
Your German is probably way better than mine, so unless I misunderstand it, I think the text is pretty clear on the matter. BBW garnets are essentially the same as those in Coticules, just different in size and content.
BlueDun said:
Very funny that you mention that. Because that is in fact precisely what a Coticule does. Granted that there are many Coticules slower on slurry than a DMT-E (1200 mesh), there are also many Coticules that rival it for speed.
Although Coticules have been used for that purpose for ages, the recent opinion about Coticules is that of a "finishing" hone, and modern marketing likes to make clear distinctions between "bevel working" grits, "intermediate" grits and "finishing" grits. Why sell only one hone, where one can sell three? But the truth is that Coticules can handle edge roughness left by a 600grit carborundum whetstone and takes it from there all the way up to a level that provides an excellent shave. I don't think that adding even coarser cutting particles on top of it will be of much benefit, because only a damaged razor requires to start on hones coarser than a Coticule. For knife sharpening this might be different, although I have sharpened pretty beat up knives' edges on a Coticule without much trouble. I don't even bother going to water in such cases, because that kind of keenness doesn't survive the first cuts on i.e. a wooden copping board anyway.
BlueDun said:
As far as influence on honing speed is concerned, I hope to be able to measure that over a few days, when the Abrasion Tester that Ralfson build for me arrives. It's a device that aims to measure speed of abrasion, while ruling out the human factor.
But there's also the influence on the rest of the procedure: how easy (or difficult) it is to refine the edge with a dilution strategy, or how the particular slurry stone affects the "slurry-dulling" effect. These parameters can only be determined by practical use, combined with repetitive sharpness tests, and good log-keeping. And most importantly, an inquiring mind. I spotted one, while reading the post(s). That's why I made the offer.
Kind regards,
Bart.