Thread: Slurry Dulling

Originally Posted by Jimbo

I never really understood the nagura progression thing to be frank, except as a traditional way to hone and as a cheaper way to hone. The way I see it it is just a normal honing progression with slurry rather than stones.

spot on IMHO

I think the difference is that the coti is one stone one slurry and you have to do a whole range of work with just that stones grit potential. Basically you have to make the stone aggressive as possible in the start and then by thinning bring forth slower but a more accurate abrasion. At least thats how I see it. Other stones are not used this way. With Jnats it would begin with coarse nagura then progress to finer nagura and finished eventually on the base stone it self if that stone was of finishing quality. Synths and other naturals stones can be used with slurry also but you wouldnt want to finish with a 1k or set a bevel with an escher. those stones are more specific to the task. Its the coticule that drives people crazy cause it tries to be too many things. Sure it can be done but it may not be easy and I think the quality of the stones ability has to be understood.

Yes, that's pretty much the conclusion I came to as well. So if you are experiencing slurry dulling with your coti you are most likely not using it properly.

James.

I'm not sure the Dulling/Limiting terms are interchangeable. The OP asked about 'dulling'. The answer is very simple, the term 'dulling' is correct because it was termed for people learning to use a coticule, who would take their basically shave ready razor that was beginning to pull, raise a slurry and hone, and then find it was worse than when they began. Hence the slurry dulled the blade. It is definitely so when you look backwards, i.e. from sharp to dull, and not forwards - from dull to sharp. The term 'limiting' can only be used from dull to sharp. Both good terms, imho.

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?

Because of this:

Originally Posted by Razorfaust

The slurry acts on the blade in many ways you have abrasion happening at the the bevel where the stone contacts the steel, or more accurately rides above it on little garnets lets say. You also have garnets bashing the front end of the edge. Steel is being removed from bevel face and making the blade sharper and the stuff hitting the front also is dulling it, at some point an equilibrium of the two forces happens when the edge gets fine enough the garnets hitting the front wont allow any more refinement of the apex. You need to get rid of the garnets swimming around in front of the blade to make any more progress or your just sand blasting the edge. So dilution or even no slurry at all will in fact get you further at this point removing that negative effect on the blade edge. From this point bevel steel removal refines the apex with no more slurry garnets dulling the edge back down. That's finishing the razor otherwise your just spinning your (garnets) wheels

In short, coticule slurry does three things: it abrades steel, it deteriorates the edge and does not break down. Because it does not break down, it will reach what Razorfaust calls the equilibrium of damage done to the edge VS the level of abrasion. By diluting you reduce both the abrasive speed, but also the amount of damage done to the edge, allowing for a keener result.

Deteriorating sharpness is effectively dulling. Hence slurry dulling. It's quite simple.

Originally Posted by Pithor

Because of this:



In short, coticule slurry does three things: it abrades steel, it deteriorates the edge and does not break down. Because it does not break down, it will reach what Razorfaust calls the equilibrium of damage done to the edge VS the level of abrasion. By diluting you reduce both the abrasive speed, but also the amount of damage done to the edge, allowing for a keener result.

Deteriorating sharpness is effectively dulling. Hence slurry dulling. It's quite simple.

The whole explanation above including the quoted portion (not reproduced here) makes wonderful sense but has a basic flaw when examined logically.

IF garnets do not break down and IF slurry is present and improving the "apex" because the blade is riding above the stone on the grit and IF the same slurry is impacting the leading edge causing dulling, leading to stasis. It can only be assumed the action of the grit (garnets) does not change with their density in the honing solution. Therefore, that same stasis will be achieved regardless of the slurry density.

So what changes to make the above statement FALSE?

Originally Posted by Splashone

The whole explanation above including the quoted portion (not reproduced here) makes wonderful sense but has a basic flaw when examined logically.

IF garnets do not break down and IF slurry is present and improving the "apex" because the blade is riding above the stone on the grit and IF the same slurry is impacting the leading edge causing dulling, leading to stasis. It can only be assumed the action of the grit (garnets) does not change with their density in the honing solution. Therefore, that same stasis will be achieved regardless of the slurry density.

So what changes to make the above statement FALSE?

There is absolutely zero evidence that what is described above happens when honing on Coticule. A bunch of guys that like to theory-craft got together and decided that the slurry works that way...OK. But those people seem to have forgotten about water suspended particles in tight spaces tend to abide by the capillary action which should push the slurry on either side of the edge and the contact with the very edge will be minimal to nonexistent. This one of those hes said she said type of stories that are tailor made to explain something a phenomenon that does not exist or is of a different nature.

Well zero evidence or not evidently when slurry is used this happens when slurry is not used it doesn't. maybe the abrasive particles suspended in some water just politely get out the way of the edge, maybe ones honing stroke or style or speed I think we could go on and on in relation to variables. For me slurry garners little favor in the very final stages of edge development I want the flattest cleanest finest qualities of the stone in use available at this phase of the honing progression. Why use slurry? To me its the equivalent of an abrasive amoeba. A relatively formless abrasive media only given its shape by the underlying plane it sits. When we are talking apex formation in the micron scale why use such an imprecise media. My 2 cents.

I don't believe there is any evidence (beyond circumstantial) to prove or disprove either theory. In the end it is all a bunch of guesses based on experience. I personally tend to believe pithor, Bart's, Razorfaust, and many others theory of slurry dulling only because this also tends to be my experience too and makes the most sense to me. It doesn't mean it's right and without fault but until science proves otherwise I am going to side with the majority here. No offense offered to other theories.

never had much success with slurry on my Norton stones. If i create slurry with a flattening stone (coarse dmt), i get better results when i rince it off the stone first. Make any sense?

Nice discussion btw....