garyhaywood said:
Bart when you explain . Speed with water moderate or slow. Which type would you prefer slow or moderate? I take it moderate would refine more with water and slow would'nt do much. Or does it just take more laps with the slow coticule as apose tom the moderate coti take less laps. They both do the same job but one is just a little slower? Or does it mean the moderate coticule will do a better job with water? the slower one has'nt got enough cutting power to pick up keeness? If you could explain if you understand what i'm asking.
It's a very interesting question, Gary. But one that's impossible to answer.
In theory, a slower hone cuts more shallow. The shallower a hone cuts, the keener and smoother it can define the edge. A faster hone will always leave deeper groves, which makes a slightly rougher edge. But an edge can also lend performance out of a slight jaggedness. Which is the first paradox in this story. Faster Coticules (on water) seem to deliver "crispier" edges. They shave very well leave a nice freshly shaved feeling to normal skin. Slower Coticules (on water) tend to deliver the smoothest edges, that leave normal skin unaffected. They do require perfect keenness in order to shave as close as the crispier edge. That's the challenge on a hone that leaves edges without bite.
Yet, hitting keenness with slow hones can be a challenge, not only because they're slow and take more time. If that was the case, we'd just had to do more strokes. For a practiced Coticule-honer that easily does 50-100 strokes per minute that poses not much of a problem. But there are other principles at play that can prevent the edge from responding well.
Badger&Blade member "mparker762", of whom I regret he's not a member over here, has explained it in perfect English:
mparker762_at_Badger_and_Blade.com said:
To make things worse, however, the edge takes a certain amount of damage just passing over the hone, from swarf and surface irregularities etc. Under normal circumstances (narrow bevel, light pressure) the damage is light enough and enough steel is being removed by the hone to keep this damage at a fairly low level so the sharpness improves. But with a wedge and a fine hone there's just not enough steel coming off to remove all the damage done on each stroke, so the damage accumulates and the razor won't get sharp like a full hollow would, and can even regress. You run into a related problem with high-carbide-content steels like stainless and TI's C135 steel; the carbides are so wear-resistant that the bevel isn't being abraded enough, yet the edge tip is still taking the damage with each pass.
In other words, on a wider bevel, or on harder steel, the hone can turn out so slow that the steel removal (increase in keenness) no longer makes up for the tip deterioration form pushing the razor edge first over the hone.
This is exactly why a BBW needs that haze of slurry for finishing. Because it just is too slow for finishing on merely water.
It's also the reason why finishing with the edge trailing might have some benefit,
but only on hones that display the above described problem on the given razor. In all other situations edge first will be better.
All this means that on a wide bevel (i.e. wedges) a moderately fast finisher will leave a smoother edge than on a narrow bevel (i.e. a thinly ground full hollow razor). That's also the reason why a Unicot edge feels differently than a Dilucot edge. After all Unicot does work on a very narrow (secondary) bevel. Now, with slow finishing Coticules, this situation is a bit reverse. They might need Unicot on a wide bevel to truly reveal their magic and at the same time be at their smoothest doing Dilucot on a full hollow. Obviously, it all depends what you prefer in an edge. Personally, I often like what I call the "rejuvenated" skin feeling of a crispy Coticule edge. But other times my skin calls for the smoothest possible edge. If that happens, I know which razor to pick...
Kind regards,
Bart.
: 
Recently I came across Bart's words saying that Dilucot edges are as good as Unicot at best. So, excluding the lack of need for tape and the Zen factor - does this method offer any quantifiable advantages? Is the slight difference of the bevel angle noticeable during a shave? Or does the edge last longer? Just questions of the curious mind.