Thread: Slurry Dulling

And, Bigfoot… there are pixs…

^^^^ That was funny

https://hocktools.wordpress.com/2009...rface-mystery/

FWIW This blog may help to clarify some of the topics, it may be nothing new to anyone with experience but after some consideration it confirmed what I was thinking; particle shape may have a lot to do with it.

My understanding is that natural stones have their particles in flat layers rather than a uniform grit that has been molded/baked together.

I felt I had to contribute after Glen liked my previous comment Hope it's helpful

This one for further and perhaps more indepth analysis...

https://scienceofsharp.wordpress.com...ry-break-down/

Originally Posted by andrewmurray86

This one for further and perhaps more indepth analysis...

https://scienceofsharp.wordpress.com...ry-break-down/

Already discussed that earlier in the thread. Nice pictures prove nothing.

Originally Posted by mainaman

Already discussed that earlier in the thread. Nice pictures prove nothing.

I have embarrassed myself

Originally Posted by andrewmurray86

I have embarrassed myself

Not at all, if you find other info definitely post here.

Slurry dulling was indeed coined on coticule.be (over five years ago, I believe) and applied to coticules. As mentioned in this thread by one or two folks, simply put, it refers to the dulling/damaging effect of slurry that limits how sharp an edge can get off slurry of a certain density.

It is why you don't want to use too thick a slurry when doing bevel work, as thick slurry will remove lots of steel, but the slurry particles will have a detrimental effect on the edge to such an extent that the edge will never reach the sharpness necessary for a good bevel.

It is why you dilute the slurry: you effectively reduce the ratio of sharpening particles compared to fluid, thus having less particles that damage the edge, increasing the sharpness limit. A coticule on water only displays no signs of slurry dulling, as the particles are lodged in the stone and not in the honing fluid. It is, however, too slow to do any effective sharpening (although if you did 5000 X-strokes, it probably would make an edge marginally keener).

What other word for damaging an edge in a way that prevents sharpness because of slurry particles but slurry dulling?

Interestingly enough, the Belgian blue stone displays slurry dulling to a much lesser extent - a set bevel will be noticeably sharper after bevel setting - because the particle density in BBWs is significantly lower compared to a coticule. Which is why they are significantly slower than coticules.

Interesting thread and a question that has vexed me from the beginning. What is sharpening as I see it. A geometric plane of an abrasive material which is used as a template for object to be sharpened is worked against that plane until the material (steel) mirrors the abrasive planes geometry. This is never really perfect as both materials affect each other and the result is usually a small compromise. It is difficult for me to understand the role of slurry in this process other than some of the slurry is trapped between the blade edge and the base stone. I also usually never see visual evidence of the slurry going under the blade unless the stone has a valley or the blade is warped in some way. I make a stroke and the slurry is squeegeed away with most of it riding in front or over the blade as I push. I understand as i flip the razor that slurry winds up sandwiched between the blade and stone and the next stroke forces it under the blade to affect abrasion. I still don't understand why this is good or even necessary as the muddy slurry seems to wreak havoc in many ways on the steel to stone contact and am going by pure belief that something good comes of this. Now where fast metal removal is concerned I can understand maybe why this is helpful but as the edge gets finer and apex geometry becomes more sensitive how can all these particles banging into the razor edge and riding over under etc. be productive. my gut feeling says no, but that's all it is a gut feeling. As I see it the very finishing of razors no matter what stone is involved seems require that slurry be omitted or used in the most diluted way. So my question is why use it in the first place other than the typical Jnat user that is using different grit stones on a base stone to extend the range of that hone, I get that. But if you have different hones why use it at all? Tradition? I wish there was more real science behind this so I can get my head around it.

Your intuition is right faust about dillution reducing errant damage to the edge. Much like going from an 80p belt sander, up to 500p RO paper on wood. One is rough shaping and doesn't do well to distinguish between the desirable and undesired parts of the board- it lies in the hands of the carpenter. The other is much slower, and much more stable in its removal. imo and experience with dilution- to me not diluting or allowing the slurry to regress in hydration is almost always a step backwards and an error, akin to hitting the stone with the edge- the fancy name ony serves to add mystique and further shroud what is - an error.

Stone regression is a real problem to, I find that when sharpening on a shapton glass 6k, that a few laps on my chosera 1k cause regression dulling, so I suggest people look out for that.

however-- there ARE stones that finish as good or better on light slurry vs totally clean. On jnats for example, there are some patterns on some stones that are commonly invasive with grain irregularities- I almost always hate goma on a razor stone- most always it will cause unsettling feedback at the edge without adjustment, but- with naguras or tomo, or a light DN slurry- you can sometimes ride over these grain biases/ irregularities. It happens with Kan as well, and stones that have these beautiful features while not having any scratchiness are treasures. as glen and many others have posted in this thread already- it fills in the low spouts- not too unlike grouting a tile floor. (you clean the xcess grout off though- everything within balance!)

Same is why you use slurry (you have just the tops of the 'heads' sticking out on a stone surface, like a crowd of people viewed from above, if you take some people out of the crowd and have them lying on top or standing on the heads of the crowd- your level of variance is greater- this is what grit helps to indicate- the variance or standard deviation of peaks and valleys. throw some sand on top of your finisher and it's suddenly more aggressive (yes it's a different sized particle, but this is a simple to view demonstration of slurry and how a lot of it can make a coarser, wider deviation of peaks and valleys) So that is the reason and mechanism by which slurry adds speed.


Back to how it can add fineness on some stones:

It provides a buffer that can be broken down and it is very evident that the binders break down and allow the grit particles themselves to act in smaller groups and eventually individually- when using Ban or Atsu even botan and yae botan to set a bevel- this is very evident, as with too much pressure, or laps without refreshing, your cutting speed falls off and it begins to do more polishing than cutting. Refresh, and you're cutting faster again. The molecules of H2O in block of ice on the table are relatively identical to the molecules of H2O in the air after some of the ice has melted and evaporated, and again to when they condense in a low VP point on a cold object in little droplets- all this conjecture of particles not breaking down is silly semantics. I might argue that particles are gluons, quarks, leptons, and baryons .. are particles, and SiO2 and SiC aren't- their molecules, and grits are large groups of molecules and the molecules are all the same size whether it 220g or 12000g- 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.
"You can know the name of a bird in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird... So let's look at the bird and see what it's doing -- that's what counts. I learned very early the difference between knowing the name of something and knowing something." -Richard P Feynman

Until I see proof otherwise, I am remain pretty sure that "slurry dulling" is an overly ambiguous and mystical name for "rookie mistake" (experts make rookie mistakes too) or "I missed the boat" that demonstrate an inability or unwillingness to accept and understand what has happened, and learn and move forward- and act as a disservice to newcomers by shrouding it further in mystery with ambiguous blameless terms. It's manufactured opacity. The other mechanism of action they might be reffering to is over honing- look at the edge damage and harshness of too many laps on a suehiro 20k. - the more random and misplaced gouges there are in the edge, the more damaged it is and likely to roll or snap off. If your playing jenga with the edge, and not "filling in the voids" (rather condensing the gaps between peaks and valleys in the steel) you are doing nothing but reducing the keenness. 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.

Just my thoughts and opinions take them with a grouped mass of NaCl particles if you like.