Thread: For guys who have a hard time getting a good coticule edge

Thanks for the post, ekretz. It's always nice to hear about someone's honing style on the coti.

I don't think absolutes are very wise in the honing section. Firstly, you are talking about a lot of variables, secondly you're dealing with a practical skill and third, the human psyche.

I have about 25 cotis now. I think they are all different and each requires a slightly/significantly different method of use. One of them, 8x2.5, which was in a rosewood box is interesting. Even rubbing with a slurry stone barely produces any slurry. Almost none. I have to use a diamond plate and even then it's (comparatively) minimal. But I'm sure if I did 100 strokes and looked at it under a microscope there might be at least one floating garnet. Would that be slurry? haha. I'll try and get back to you with the result.

Thanks again for the idea.

Everyone defines such things in their own way of course (YMMV is a popular phrase for a reason), but yes, to me any stray grit that is shed from the stone during use is auto-slurry. Those stones that shed very little are easiest to finish on when the particles are fairly large (like coticules).

And I'll say again that surface preparation/finish plays a significant role in the volume of shed grit, or auto-slurry. Take the Coti that you described and lap it with a relatively new 400ish grit diamond plate and I'd wager it will auto-slurry quite a lot compared to what you describe. Take a softer coti and polish it up to a 2k finish and it won't give up a whole lot of grit at all with light pressure honing.

Another thing to keep in mind is that auto-slurrying isn't always a bad thing. For some stones it can actually make the edge more comfortable on the face, for whatever reason.

My thoughts are as follows.

If we describe auto slurry as an unwanted shedding of grit. My question is how do we detect this auto slurry? Is the swarf that shows up on water only indicative of auto slurry to you? A cloudiness? I'm just curious is why I ask.

Out of all my coticules I have not noticed them auto slurry in a detrimental way. The only time they slurry is rubbed with a slurry stone. Repeated water only strokes either the water stays clear or on the fastest specimens , steel is removed from the edge and visible swarf is seen. The edge doesn't lose any keenness rather refines that last but if the edge wasn't already there.

Just my thoughts correct me if I'm wrong.

In my experience it can be seen in a couple ways. Foremost, with a wipe of a clean white cotton cloth yellow particles will show up - by wiping they are concentrated into a just visible yellowness against white - a darker cloth may actually work better for this in fact; and second, if the bevel is examined under a microscope after honing there are very obvious anomalous deep scratches when no rinsing and scrubbing of the stone has been done. When the rinse/scrub method is done these are minimized to nearly the point of elimination.

Also in my experience, on many coticules rapid black swarf production is an indication of auto-slurry, the black swarf just hides it very well.

I don't mind the discussion/questioning by the way. It's enjoyable to me and who knows when we may collaboratively discover something useful through the discussion, or get an idea for further testing etc.

Originally Posted by eKretz

Also in my experience, on many coticules rapid black swarf production is an indication of auto-slurry, the black swarf just hides it very well.

OTOH a very hard yet fast cutter may simply have a high proportion of garnets. My La Veinette is like this.

Yes, that is so, and that is why I worded it how I did - many coticules, not all.

Originally Posted by onimaru55

OTOH a very hard yet fast cutter may simply have a high proportion of garnets. My La Veinette is like this.

So is mine, an Old Rock, like a bed of Garnets and Glass shards.

Another surefire way to tell if your stone is really giving up any slurry that you can't see is to do your normal finishing with water then let the stone dry without rinsing or scrubbing it. After it's had a chance to thoroughly dry, use a dark cloth to rub the top surface of the stone - slurry will show up as a fine powder embedded in the cloth. I think some of you that think your stones don't auto-slurry at all might be surprised by the results of this test.

Originally Posted by eKretz

Another surefire way to tell if your stone is really giving up any slurry that you can't see is to do your normal finishing with water then let the stone dry without rinsing or scrubbing it. After it's had a chance to thoroughly dry, use a dark cloth to rub the top surface of the stone - slurry will show up as a fine powder embedded in the cloth. I think some of you that think your stones don't auto-slurry at all might be surprised by the results of this test.

Does it really matter if the edge is good ?
It would seem that little / no slurry is not an impediment to a good edge.

Of course not. The point of that post was that just because slurry isn't visible doesn't mean it isn't there. I wouldn't have brought it up at all if I hadn't been asked about it in post #23 - this way it's easy for anyone who would really like to know to check for themselves; if anyone doesn't want to check that's fine, but for those who do, it may provide an avenue to get to an even better edge than the one they thought was their stone's best. I've already mentioned that no one method is going to work for every stone - one ought to try every method with an unfamiliar stone to find what works best if looking for the best edge any given stone can provide.