(backup from Coticule.be)
Advanced Feedback Markers
Last updated on: 2010-11-04 00:15
[article still under construction and reformulation]
Feedback and the Dilucot procedure.
I am a strong proponent of using (almost) all senses while honing on a Coticule. Mindfulness does not only offer advantages for those who seek Zen-like experiences in honing. It also pays off to familiarize yourself with how a Coticule “talks” to you while honing.
It is impossible to offer direct markers, that will give an exact recipe for best results. There is too much variance between Coticules for that. Sure, you can see the slurry turning gray (or black) on all of them, you can perceive the almost blood-like scent of iron particles entering the mixture, and you can hear the garnets work the steel. But these are all parameters that are hard to quantify. There are other aspects to focus on, but no matter how many words I write about them, they will never substitute the need to develop some sort of intimate relationship with your Coticule.
For those who want to become really proficient with the Dilucot approach to honing, I cannot emphasize enough how important it is to practice on one hone. I don’t think anyone can ever truly reach that point of almost total awareness about the condition of the edge at any time during the honing sequence, if one’s not prepared to be faithful the one hone for an extended period of time. I am not saying that you can’t get a good edge of a Coticule without that kind of conversance with a particular Coticule. Only that beyond “good”, waits a whole new world of smoother and keener edges within reach of the Dilucot procedure, for those to discover, who are prepared to hone razor after razor after razor on the same Coticule.
Fairly obvious, but I’m mentioning it anyway. The steel you are removing has no choice but to show up in the fluid on top of the hone. Even on plain water, if you look very closely, you will find evidence of that. If an edge still lacks a small touch of keenness during the water phase, you must make sure to remove that final bit of steel. If you don’t see it, you’re merely polishing, which does nothing for the keenness of the edge. Maybe some half-strokes on pure water, will do the trick (watch the fluid). Maybe X-strokes with a hint of pressure (watch the fluid). Maybe one rub with a slurry stone before you continue (watch the fluid). Get some steel off those bevel faces and refinish with your normal lighter-than-the-weight of the blade strokes. You could be surprised what you might still be able squeeze out of your edge that way. This approach does require some consistent and repeatable way to probe for sharpness. I use the HHT (as described in this article!) myself.
Slurry can be made (or kept) thick or thin, but there is more to it than just that. Some Coticules generate a jelly-like slurry, that behaves like soap when thinned out. There’s even a consistency where the slurry starts foaming a little, although I have not yet found a special advantage to that. Jelly- or soap-like slurry does tend to stay better on the hone, and that saves us from additional rubbing with the slurry stone. A practice that may interfere with a proper and steady dilution. Dilution must not be done too fast, but you mustn’t wait too long either, because drying slurry works backwards. Jelly-like slurry shows far less tendency to dry out than a more putty-like slurry. It allows for slower and more precise transition through the dilution stage.
Fortunately, there are ways to improve the consistency of the slurry.
You could add a few drops of soap to the honing water. Note that this does reduce the abrasive power of the hones, most notably when working on thinner slurry and on soapy water. You can try turning that into an advantage, but because it adds another, somewhat difficult to control, variable in the honing process, I stopped using soap or detergent long time ago.
My preferred method for improving slurry texture on hones that need it, is to add steel to the mixture. That’s right: steel. Those who’ve done bevel work on a Coticule will have witnessed how grayed slurry behaves much more gelatinous than non-grayed slurry (except on those hones that have excellent slurry texture to begin with). Therefore, if you don’t need to do bevel work, you could still raise a good slurry and rub it with a piece of iron for a few strokes, before you thin it to the required concentration. You’ll notice that it catalyses the texture of your slurry and helps it to stay better on the surface of the Coticule.
One other solution, that I plan on thoroughly testing in the future, is the influence of the slurry stone. The properties of the slurry stone will certainly contribute to the behavior and texture of the slurry. We will probably start adding slurry stones to the Coticule Vault in the nearby future. Stay tuned for that.
[the concept of “undercutting” is illustrated in the picture in the left column]
As explained in the “honing strokes” article, the wave of slurry running up and in front of the edge offers excellent guidance for conducting a good honing stroke. But it also gives you a fair idea about keenness during the finishing on pure water. Even a thin coat of water should be undercut by the edge. If not, that may be caused by minimal deviations in the blade’s straightness (warp). If true, on one side of the bevel, the affected part of the edge will undercut the water just fine, while it refuses to do so on the opposite side of the bevel. In this case, you should adjust the roll in your stroke and catch up with the underdeveloped part of the edge.
If however part of the edge refuses to undercut at both sides of the bevel, you must reach a bit back into the honing sequence to reclaim the neglected keenness. What I wrote above in the Slurry Darkening paragraph could be just what the doctor ordered.
Surface Draw and Abrasive Feel.
The sensation that can be felt in the fingers that guide the razor can be defined in 2 parameters, that are closely related.
The first is draw. Draw is a slight resistance to push the razor over the surface. It is also directly affected by the width of the bevel. Wider bevels cause the hone to draw more than smaller ones. Draw is not much altered by the fluid on the surface, whether it is thick slurry or plain water. Draw cannot be heard.
The second parameter is abrasive feel. This is marked by an extremely fine sort of graininess that can be felt while using the hone. It is largely affected by the fluid on the surface. Thick slurry might offer a truly grainy feel, while on the same hone, all abrasive feel can disappear on plain water. Other specimens show a less spectacular drop in abrasive feel and still retain some of it on pure water. Abrasive feel can always be heard as well.
Both parameters influence the point where the hone will stop offering edge refinement and turn into a mere polisher. Some Coticules keep refining all the way till the very end, some start polishing during the last steps of the dilution stage. It is imperative that you hit the keenness limit of your hone, before you reach the aforementioned point. At the same time, it is equally important that you do not run too far in front of the refining edge, because it will stop following. It a good habit to increase your lap count, as you start to approach the “suspension” point of your Coticule. On many, but not all Coticules, a good plan is to rinse the hone and razor under a running tap, without touching them. The slightest hint of slurry will remain present, and you can stay on it till you are fully pleased with the aforementioned “Fluid Behavior”. Only then, rinse and clean thoroughly before finishing on pure water.
Illustrations – click to enlarge
Edge undercuts slurry – picture by Enrico Marchesi