Thread: Slurry Dulling

I just know from my own experience that a heavy slurry will cut more aggressively & while slowly diluting it will eventually get a keener polished edge & eventually finishing with water only. Once in a great while, I will encounter a piece of grit & stop there, rinse off my stone & go back to my previous stone starting over with that one just in case it got a scratch, rinsing it often to keep from happening again, then proceeding where I left off. My final strokes will get less & less water to polish the edge to a finer keen finish. I will then strop on the fabric about 15-20 strokes with crox or .25 diamond spray, then around 75-100 strokes leather. I don't have enough experience with Jnats to comment on them yet. I hope to in the future.

What's in a slurry? It has to be water plus stuff from the hone plus, as you work the razor, teeny tiny bits of metal, right?

The stuff from the hone can only be the abrasive particulates plus the (for lack of a better term) hone substrate - the stuff that binds the particles.

And miscellaneous other things like some dust particles from the air, spider poo, etc that probably don't matter all that much. Or do you guys all hone in a hermetically sealed chamber...?

So then it just boils down to the particulate and the substrate initially, and then as the honing goes on a more complicated particulate/substrate/metal bits interaction.

How you release the "slurry" probably plays a role. If you rub the hone surface with a diamond plate you are probably ripping out chunks of substrate with particulates inside or attached, making little "nano hones" which are not lapped and just float around in the water doing their thing.

Their thing is breaking down with friction I guess, and releasing the particulates they had embedded in them.

That's all I've thought about so far. I have no idea what it means.

One thing I will say is that I have noticed on more than one occasion that if I've used a mild slurry on my finishing Jnat (raised with a diamond plate) the edge doesn't plink arm hairs as crisply as it did immediately prior to the slurry strokes. However, after stropping that slurried edge it plinks arm hairs much better, usually.

This to me means/suggests plastic deformation has happened. Only suggests, since I have never shaved straight off the hone - always stropped first. So all this could just be that my arm hair plinking technique is off.

James.

Originally Posted by engine46

I don't have enough experience with Jnats to comment on them yet. I hope to in the future.

I will loan you one of mine for a month if you'll take care to send it back equally well packed and insured. Then we can all be opinionated about jnat slurry. Just PM me if you like.

Jnats, schmaynats. The term "slurry dulling" was coined specifically in relation to honing on a coticule. Coticule slurry does not break down; Japanese natural slurry (as far as I understand) does. So if there would be slurry dulling going on when using a slurry that breaks down into a finer slurry, the slurry would polish finer and finer as well as having a reduced slurry dulling effect as it breaks down, making the slurry dulling a non-issue.

Originally Posted by jnats

I think experts don't like to say- "sometimes I forget or struggle to get my timing of dilution just right and take the edge back a bit and wind up having to remove more steel and hone longer than if I had done it right the first time." and it's easier to remain infallible and blameless by inventing a mystical scapegoat term "Slurry dulling" I agree that it is a lot like religion.

Except that it's not. The experts that came up with the term? Over on coticule.be, a lot of people I would consider more or less advanced users of/experts on honing with a coticule (who use the term "slurry dulling") mentioned their many (old and new) mistakes, problems and issues. They tended to blame their lack of skills on and understanding of the tool they were using, rather than the tool itself. They were quite a humble bunch in that, and never presented themselves as infallible.

If you want to see the effect of slurry dulling:

Take a coticule, raise a slurry, get the bevel set on a known well-performing razor and test for sharpness (as in: make sure the bevel is definitely properly set). Keep honing on the same slurry while adding one drop of water (to prevent the slurry from drying out) every thirty or so back-and-forth strokes for five/ten/fifty thousand minutes and test for sharpness again.

My bet is that you will see no significant increase in sharpness. That is slurry dulling. That is why you dilute. On slurry, there is a plateau when an edge will not get sharper without diluting.

Originally Posted by Pithor

J
If you want to see the effect of slurry dulling:

Take a coticule, raise a slurry, get the bevel set on a known well-performing razor and test for sharpness (as in: make sure the bevel is definitely properly set). Keep honing on the same slurry while adding one drop of water (to prevent the slurry from drying out) every thirty or so back-and-forth strokes for five/ten/fifty thousand minutes and test for sharpness again.

My bet is that you will see no significant increase in sharpness. That is slurry dulling. That is why you dilute. On slurry, there is a plateau when an edge will not get sharper without diluting.

In your thoughts the edge reaches a plateau and remains there. I see your point. But then why is this called dulling?

Originally Posted by jnats

I would of course be wrong and debating a silly thing, as it's semantics and particles of gypsum dust or sand and dirt or gluons are all particles- it's a word, and it has multiple uses and frames of significance.

Originally Posted by 32t

In your thoughts the edge reaches a plateau and remains there. I see your point. But then why is this called dulling?

Perhaps these two thoughts are not unlinked...

While its easy to dismiss things we disagree upon as silly semantics, perhaps the term dulling is not referring to the edge but the slurry itself? .be is the Belgian domain so perhaps we have misunderstood what they are referring to?

Perhaps slurry dulling is the process of the slurry becoming dull or rather reaching the end of its usefulness at that particular dilution?

Just a thought. I'm no expert at honing or using coticules but I am rather excellent with language.

OK, I can work with that as a definition. My question is then why? What is going on that undiluted slurry is not increasing the sharpness/smoothness? Is it providing a barrier between the edge and the hone surface so that new garnets are no longer being released or exposed? Or are they being exposed but at a sub-optimal rate? What is it about diluting the slurry that increases the abrasive power of the hone?

It sounds like there's a slurry sweet-spot. No slurry seems sub-optimal. Too much (undiluted) slurry leads to a sub-optimal outcome as well.

James.