Thread: Assess coticule quality?

Hi everyone,

I am trying to touch up the edges of two razors on a coticule. The first is a Dovo I got from Lynn a couple of months ago (was a perfect shaver upon arrival) and the second is a TI I bought new about 3 years ago. Now that I have felt what shave-ready feels like (the Dovo), I can confidently say that the TI has never been that sharp.
After considerable work on the coticule (30-50 laps with and without slurry), both razors pass the marker test and "almost" pass the HHT: hairs split but do not pop... and the shave test felt rough
Because this is my only hone, I cannot tell whether the poor honing job is caused by the hone, my technique, or both... Therefore, is there any way to assess the quality of a coticule, next to the honing result? I have read somewhere on this forum that the quality of natural hones can vary... As all coticules look more or less the same, I suppose it does not make sense to put a picture of my stone online... wait, there is a small grey-black spot (about 0.5" by 0.25") on the (yellow) honing surface

Any ideas?

Thanks in advance for your assistance!

Best regards,

Tim

While I do love my coticule I wouldn't try shaving off the stropped edge. I at least use the CrOX strop with 10-15 laps afterwards or even finer hones (Thuringians for example).

Good question.
Different veins do exist and each vein caries a number of coticule layers, separated by Belgian Blue stone.
In the old days, raw coticule was always triaged, based on the layer it was harvested from, and even then they differentiated in purity of the stone. Some layers were considered "razor quality" while others were used for honing other tools. Even within razor hone category, there were different grades. But those were the old days. People were honing razors entirely on coticules, without going to coarser stones when more work was needed. A razor quality hone needed to be fast, very fast even, because you can't put pressure on a razor blade while honing, in the way you can push down on, let's say, a chisel, or a butchers knife. So, a lot of the gradation is about cutting speed, which is not of great importance, because nowadays, most of us use the coticule merely for polishing purposes and not for bevel restauration. I have a few different stones, and the difference in cutting speed is very obvious. You can tell something about the speed of your coticule if you observe the slurry. The slurry of fast coticules will turn grey (from the metal particles it is eating) almost instantly. Others will take many laps before you notice a little discoloration.
But they differentiated between fineness too, in the old days. I have a copy of a book that describes many different coticule layers with comments about the fineness of the hones they produce. At Ardennes Coticule (the only operational quarry) they don't sort the hones today. I think it would be very difficult to start doing that again, for the entire production, for reasons of the modern quarrying techniques they use. (dynamite as opposed to dangerous, but meticulous mining of stones 30 meters below the surface in unstable mine shafts) They have plans though, for grading at least part of the production, especially the part that's meant for razor aficionado's .
The question remains: how big are those supposed differences in fineness? From where I stand, not all that big. Perhaps even, not noteworthy big. I have access to 7 different coticules (and more to come), and there's not a single one that refused to put a good edge on a razor that required anything else to be qualified shaveready. Sure, one can still step up to Chromium Oxide, or other types of finer (and rather expensive) hones and push a razor further up the keenness ladder, but one can also shave right of any of those coticules for the rest of a lifetime and that's exactly what I'm going to do.
It's impossible to tell, without some serious double blind testing, if and which one of those 7 coticules puts the finest edge on a razor.
As it stands, I have 8 identical razors on the way, and have planned a series of comparative tests, together with a straight shaving friend. Not because I doubt the quality of certain coticules, but because it seems like an awesome and fun idea to do all kind of experiments with different honing methods and different coticules.

Nevertheless, I think you should post a picture of that coticule, just because many of us like watching them .
As for your specific problem with honing your razor, i'll put that in another post, because not every one likes to read long posts.

Bart.

For the longest time my coticule was the last stop in my honing process. I never needed anything more as it put the ultimate edge on most of my razors. Even though I have added some more stones and they provide a slightly different result in general my coticule is still my go to stone for final polish. But as to your question, there are coticules that give a vastly poorer result. It would depend on the distribution of the garnets, the size of the xtls and the type of xtls and the type of garnets.That is why it is very important to know your stone provider and trust in him. As to whether your problem is a stone problem or technique problem or a combination the only answer is to have someone highly skilled use the stone and let you know.

Tim,

You should know that, while a coticule with slurry removes metal efficiently, it also has a tendency for rounding the very last bit of the tip of the cutting bevel. A perfect shaveready edge starts with a bevel tip width of 0.5 micron or less. Clearly coticule slurry causes the bevel tip to broaden a bit to a width that shaves but only marginally. The denser the slurry, the more pronounced that effect will be. Please bear in mind that the granats (a sort of spiky balls that do the grinding, mixed with water to form the slurry) are approximately 15 microns in diameter. Pushing your edge through that slurry is a bit like pushing the edge through mud. It eats metal from the sides of your bevel, but also from the tip.
That said, the frist thing to try is to start with a rather dense slurry, but never denser than coffee cream consistency, do 30 laps or so, adding drops of water as soon as that slurry starts to thicken. Keep at that, till the TNT or even better, the TPT starts telling you, that you've maxed out with what your doing. Then, lower your already low pressure to the bare minimum. Performing the strokes with some speed helps. (You can turn the razor over the spine as slow as you wish, but the strokes are generally lighter with some speed). Watch that slurry, don't allow for it become any denser. See if you can gain a bit more by performing another TPT. (Stop using the TNT at this point, for it may dull what you are gaining). If you maxed out again, then start adding 2 drops of water every 10 laps, slowly allowing that slurry to dilute till the point where you have only water. It should take you about 70 to 100 laps, from slurry to water. Now, rinse that razor, wipe it dry with some tissue paper, and get to your strop. Do at least 50 laps with enough pressure to feel a clear draw. Keep that strop very taut. After that strop another 30 with just the weight of the razor for pressure.
Try the HHT.
You should have a great shaving edge now.
Please keep me posted, I have a few other tricks up my sleeve, that were successful in countering the dulling effect of coticule slurry.
I believe it is the reason that most people do the initial bevel work on a DMT1200 or another fast cutter, and use the coticule only with water for polishing that already sharp bevel to shavereadiness.

Just a simple question.... have you lapped that coticule flat?

If not, then do so. It will make a big difference.

Thanks a lot for your help guys!

@Bart: For some reason I cannot produce slurry thicker than let's say regular milk (both in consistency and color)... With the small rubbing stone (coticule) I cannot get it as thick as coffee cream... also, the slurry does not turn grey during the honing process.

@Randy: How should I lap the coticule? Does it suffice to rub the small coticule over the honing surface?

Tonight, I will give it another try...

Thanks again,

Tim

I have used a more haphazard version of Bart's Coticule method and I can shave off my edges.
I know I could do better (I'm still a very green learner) by being a bit more methodical.

Here is how to lap a hone

http://straightrazorpalace.com/basic...ing-101-a.html

Tim,
If your coticule does not produce slurry easily and it does not turn grayish from metal particles, than you have one of the slower stones. With some coticules, the rock that bonds the garnets together is so hard that it's difficult to raise a good slurry. With other slow coticules, the garnets themselves appear to be slower. From the information you provided, my bet is that you have the former case. Probably a great polisher, but not much of a metal eater.
But, my friend, do not despair, a stubborn horse often rides better then an indulgent one, once you learn how to tame it. :-)
First off, your hone should indeed be absolutely flat. If not, you need to look up Josh Earl's tutorial thread for lapping hones, and get it properly lapped.
Here's your new improved slurry raising recipe for callous coticules: fold a piece of 220 grit (other grits might work too) sandpaper around a small wooden block. Use that sanding pad on a dry coticule (that's right, no water, not just yet). Sand the entire surface till it is covered with fine coticule dust. It won't take very long. At this point, add a few drops of water, and use your cotigura stone to mix the dust with the water to a rich slurry. Add more drops of water and smear till you're happy with the consistency. With this slurry you should be able to remove metal and witness how it darkens to a rich gray, within 30 to 50 honing laps.
Should your stone be the latter case (slow garnets), than, no matter how nice a slurry you raise, it might take hundreds of laps before you start noticing the presence of metal particles in the slurry. While such stones might very well be even finer polishers, you won't be able to cut a good bevel with them. In that case, it might be better to use it only for finishing the edge and do the preceding honing part with another hone such as the DMT1200 or the Norton 4K before you jump to your lazy coticule with slurry and finish with only water.
BUT... you can also cheat that coticule into thinking it is a fast cutter. :-)
Get yourself a lightning fast and soft cotigura stone (cotigura = the little piece of coticule that you use to raise the slurry). Throw away that sandpaper and rub with your cotigura on your coticule till you have the slurry of your dreams. 80% or more of that slurry will be produced by that cotigura, but who cares. Your razor doesn't.
If you're interested in such a superior cotigura stone, PM me about it.
Hope this helps,
Bart.