Correct slurry stone

[BlueDun]

Hi folks,

I was wondering how important the slurry stone is. The reason is that I have my two cotis but I have no "correct" slurry stone to go with them. So I'm just using a natural nagura I bought with my awaseto -->

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. It seems to work well and rises a slurry just the way it looks in the videos. Sharpening is ok too.
Yet, any objections to using that nagura?

Regards
BlueDun

 

[Bart]

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I don't think it will be much of a probblem. In a pinch I've rubbed slurry with sandpaper. Worked fine too. You can also rub your Coticules together, and compare the results with your nagura method.

Kind regards,
Bart.

 

[BlueDun]

I thank thee for the advise, your royal sharpness … B)

I was thinking a bit more about the influence and importance of the slurry stone on the honing process on coticules. So I’d like to share my thoughts with you.

As I have learned there are many different coticule layers in the Ardennes that produce stones with quite different sharpening properties which show mainly in the speed. If I am not completely mistaken these differences are not that big when coticules are used as finishers with no or only very thin slurry. It is broadly acknowledged that Belgian coticules have excellent and comparable finishing qualities no matter which layer they emerge from. The large differences – and I could experience this myself on my two very different stones – show when they are used in the first stages of the unicot/dilucot process. With a significant amount of slurry that is. Obviously, it is the slurry that does the most part of sharpening during these stages and not so much the solid piece of stone underneath. The more the slurry is diluted the more the stones work as finishers. Yet, except for the very last stage when honing only on water there is still some slurry on the stone that takes its share in the sharpening mechanism. Hence, it might be worth a closer look at how this slurry is created or, to be more precise, what it is made of.

Let’s look at using “bouts” coticules as slurry stones as this seems to be common practice. When creating slurry it will be made of both, the slurry stone and the hone itself. For two rocks with equal hardness I would consider it a valid assumption that the material mix in the slurry is 50/50. If on the other hand a very hard hone is paired with a very soft slurry stone the slurry will consist to a large part of material coming from the slurry stone and vice versa. Without arguing about the actual percentage I would assume that in this case the honing properties will be determined mainly or almost exclusively by the stone that provides the majority of material in the slurry.

One can now pick on details of my argumentation or on percentages in the slurry compositions but I still would argue that the slurry stone does make a difference and that the difference can be significant. So the question for me is how does it influence the honing process and how could I possibly make use of that in order to get better results.
One option might be to match the bout with the hone in order to fine-tune its properties. It has been stressed quite often that it takes a long time to really master honing on a coticule. And it is particularly important to use one hone only and learn about its very own behavior. But since coticules are different it might well be the case that someone just does not get the hang with a particular stone and never gets the full potential out of that piece. So why not experiment with different bouts in order to tune the sharpening behavior while maintaining the “coticule-style”. Certainly, this will be a cheaper approach than buying a new hone at all.

Going one step further it seems plausible that the use of slurry stones of various materials can fundamentally alter the sharpening properties of a coticule hone. Now this may be a potential source of errors and may well be a cause why someone will not get satisfying results with his coti. On the other hand this effect can be used on purpose.
Let’s look at a BBW slurry stone for example. I have never used one myself and my considerations are only hypothetical but I’m only trying to make a point. As far as I know the abrasive garnets in the BBW are grenade particles and as such different than the ones present in the coti. But even if this is not the case it will be true for another type of stone, so let’s presume this as fact. If the slurry stone is also softer that the coti then we are back to my above argumentation: the slurry will only consist of few coti garnets and not behave like a coti slurry at all. This may be beneficial if the slurry builds and refines the bevel in such a way that it will gradually transform in a coti edge when the slurry is diluted and the hone starts to do its work. But it may also be the complete opposite if the gradual buildup of the edge gets lost sometimes during the dilution process.

Anyway, it’s getting late and I need to hit the sack. I hope I could get my points over an I’m curious about your feedbacks.

Regards
BlueDun

 

[Bart]

Hey Bluedun,

Excellent post and good thinking. I've been on that page as well. It's the very reason why I hinted to Maurice of Ardennes Coticule to include "La Veinette" slurry stones for razor honing (it's one of the properties of the La Veinette layer, that the slurry responds very well to the dilution strategy), and "La Petite Blanche" slurry stones to speed up slower Coticules. I know that he at least did that for a while when he shipped hones to our members. Not sure he still does it nowadays.

I have run a few tests, but certainly not nearly enough to draw any hard conclusions. (So much to do and so little time).
However, there is one major factor,that you are overlooking in your post.
A lot of a Coticule's honing abilities are defined by its "matrix". I'm not sure that's the correct term, but it's what I use for the minerals that bind the garnets together. Those all belong to the group of phylosillicates. And analysis had shown that it's not so much the garnets that differ between Coticules, nor their shape, width or abundance, but that there's serious differences in composition of the matrix. Most of the components are softer than steel, but some are not. Those might even play an abrasive role on their own, even while finishing. But what is absolutely key in this story, is that a Coticule must abrade itself while honing. The already present garnets abrade the matrix and this release more and fresh garnets. This is important, because garnets, though they do not break down, do loose their bite after some time. Try honing with slurry on a flat piece of glass, if you want to find out. If that would work well, we would only need to buy a slurry stone.
Bottom line, the garnets that came from the slurry stone will gradually loose their influence while honing. As said, this needs more investigation, but it appears to happen rather early in the process.

Concerning the Blue. It always has been my understanding that the garnets are pretty much the same, only larger in diameter. That doesn't necessarily make the Blue coarser. We're not dealing with spiky particles, as the one's we find in synthetic hones.
Please read this article, to know the hypothesis I'm currently adhering to, concerning the working principles of the BBW, why it's slower and displays less of the "slurrydulling" effect. I'm sure this is only a partial truth, as also the BBW has significantly different matrix than a Coticule.

But if you want to do some serious investigation, I could set you up with a few different Coticules and a bunch of determined slurry stones.

Kind regards,
Bart.

 

[BlueDun]

AAAAHHHH ... back again!

I got missing server for 2 days and did not know about the .org domain. Hey, I was missing something !!!

Let me clarify some thoughts:
I used the BBW just as an example. My point was the following: Assume you have a slurry stone that is significantly softer than the coti hone you're using. And also assume that the slurry stone is not a coti and is very different than a coti in terms of how its slurry interacts with steel. In that case the initial slurry will most likely not behave like honing on a coti at all - with all pros and cons that may go with that. The coti-like sharpening properties will only come to show gradually as the initial slurry is diluted and more and more coticule garnets are release and take the majority of abrasive particles in the slurry.
To really strecht the point, imagine to start with a DMT and end up with a smooth coti edge - all on one hone.

Yet, to come back to the BBW and its garnets. Those interested, please take the time and check http://www.belgischer-brocken.com.
German site, so here's the talk-throug for those bloody foreigners (this one was for you Dr. Ralfson):

Click "infos" on the left table. You'll see pop up a table with images and text next to them.
Click on the upper left cell that says "GBB" somewhere in the text next to it.
What you see are microscopic pictures of a coticule. Beautfully visible are the garnets like pictured somewhere else here.

Now go back to the table with the small pictures and hit the third from top - the one with the red spot.
What you see here are allegedly pictures of a Blue Belgian. No coti garbnets but red particles - presumably grenades.

Bart, I've read contradictory arguments on the composition of garnets in cotis and BBW's. What do you know about it?


Anyway, back to the topic of how slurry stones influence the hone. Might be an interesting field for investigations. I feel quite flattered by your offer make me run some tests, Bart. Did you think about how such tests could be set up in order to yield meaningful results.
I have to say that I'm a bit reluctant about doing these tests. I'm very new to razor honing let alone honing on cotis only. So my honing skills are anything else than consistent. But consistency and therefore reproducibility will be crucial in order to get usable results.

Cheers
BlueDun

 

[Bart]

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I know about a study of the University in Liège (which is the nearest big city to the Coticule region). I also own a copy of "Ardoise et Coticul en Terre de Salm", published in 2007 by the Geological Survey of Belgium (a subdivision of the Royal Science Institute). The book (in French) offers a multidisciplinary approach. Also the Belgischer Brocken website seems to agree that Coticules and BBW's both rely on spessartine garnets. I think "garnet" and "grenade" is the same. I'm no geologist, but if I understand any of it, spessartine garnets can vary both in size and color greatly.
Here's a quote from

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[note=Belgischer-Brocken]Untersuchung einiger einzelnen Granaten im REM hat uns gezeigt, dass es sich um reine Mangan-Granate handelt, den sogenannten Spessartin. Chemisch-Mineralogisch ist der Granat eine Mischkristallrreihe mit verschiedenen Gehalten an Mg, Fe, Mn, Al und Ca. Der Spessartin ist ein Endglied der Mischkristallreihe und besteht neben SiO4 auschließlich aus Mangan und Aluminium. Die Elemtanalyse eines Granaten im belgischen Brocken Gelb zeigt das mitgeschickte Bild „Analyse“, die Vorherrschaft von Si, O, Mn, Al mit Spuren von Ca ist gut erkennbar. Vorkommen von reinen Spessartinen sind relativ selten, da fast immer Mischkristalle vorliegen. Sie können aber die Granate im BB mit ruhigen Gewissen als „Spessartin“ definieren bzw. bezeichnen.[/note]
Your German is probably way better than mine, so unless I misunderstand it, I think the text is pretty clear on the matter. BBW garnets are essentially the same as those in Coticules, just different in size and content.

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Very funny that you mention that. Because that is in fact precisely what a Coticule does. Granted that there are many Coticules slower on slurry than a DMT-E (1200 mesh), there are also many Coticules that rival it for speed.
Although Coticules have been used for that purpose for ages, the recent opinion about Coticules is that of a "finishing" hone, and modern marketing likes to make clear distinctions between "bevel working" grits, "intermediate" grits and "finishing" grits. Why sell only one hone, where one can sell three? But the truth is that Coticules can handle edge roughness left by a 600grit carborundum whetstone and takes it from there all the way up to a level that provides an excellent shave. I don't think that adding even coarser cutting particles on top of it will be of much benefit, because only a damaged razor requires to start on hones coarser than a Coticule. For knife sharpening this might be different, although I have sharpened pretty beat up knives' edges on a Coticule without much trouble. I don't even bother going to water in such cases, because that kind of keenness doesn't survive the first cuts on i.e. a wooden copping board anyway.

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As far as influence on honing speed is concerned, I hope to be able to measure that over a few days, when the Abrasion Tester that Ralfson build for me arrives. It's a device that aims to measure speed of abrasion, while ruling out the human factor.
But there's also the influence on the rest of the procedure: how easy (or difficult) it is to refine the edge with a dilution strategy, or how the particular slurry stone affects the "slurry-dulling" effect. These parameters can only be determined by practical use, combined with repetitive sharpness tests, and good log-keeping. And most importantly, an inquiring mind. I spotted one, while reading the post(s). That's why I made the offer.

Kind regards,
Bart.

 

[tat2Ralfy]

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Saw it ...lol

have to say if my attention span was a little greater than it is at the moment, friends will be able to guess why this is, and yes its a good thing in the short term, I would have to what a wonderful thread this is :thumbup:

 

[BlueDun]

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Apparently so. I checked on leo: garnet (english) = granat (german)

The Summary from BelgischerBrocken which you posted does not really clarify things. In a nutshell they state that the particles found in Coticules are spessartines which is a special form of garnets (Granat). Nothing mentionned about BBW's.

Still there are the pictures on BelgischerBrocken that are quite different. The BB shows these red particles that look like the gemstones girls love so much (Called Granat in German) . The pictures of the Coti do not show these. The guy who made the pictures even points out that he could not find any.
Maybe we should advertise a mineralogy master's thesis at the Université de Liège

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: : :

Ok, let's talk about it. Maybe we'll find a way to render myself useful despite my missing experience.

Cheers
BlueDun

 

[Bart]

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What about the last sentence?

[note=Belgischer-Brocken]Sie können aber die Granate im BB mit ruhigen Gewissen als „Spessartin“ definieren bzw. bezeichnen.[/note]
I would translate that as: "One can nevertheless define the Garnets in BB (BBW?) with a clear conscience as 'Spessartine'".
Did I get that part wrong?
In any case is the study of the University of Liege and the book of the Geological Survey quite clear BBW and Coticule both contain spessartine garnets. Size in BBW varies in between 10 and 30 micron. In Coticules, sizes of garnets are in between 5 and 20 micron. (I'm quoting the lowest and highest numbers I've found in various sources).
Spessartine crystals (garnet) has Mn0 (manganese oxide) as a main component. Chemical analysis of Coticules reveals Mn0 content of 7.8 to 23.5 % of the entire mass. Within BBW, this is in between 1 and 6%, hence significantly lower.
I can only speculate that the pictures you're referring to are shot with different methods of maginification, and that spessartine crystals in BBW may be red, while very light orange to almost translucent in Coticules.
Here are some pictures of Spessarine Crystals, some as large as a marble:
[img=150]http://www.freilichminerals.com/files/spessartine3.gif[/img]
[img=150]http://www.crystalclassics.co.uk/minerals/s_5992.jpg[/img]
[img=150]http://www.cppstanzania.org/mines.jpg[/img]

[img=150]http://www.freilichminerals.com/home/finalimages/1070/sp3b.gif[/img]

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I could make a package with a few Coticules and a collection of slurry stones coming from different layers.
You could hone of them, and find out if you can correlate any differences between the slurry stone used and way the hone behaves.
I think it's best to start a thread, report experiences, and devise experiments as you go along. Obviously, we would support you with suggestions as much as possible. If you're ready after half a year or so, you could ship the parcel to someone else willing to run tests in the same field of interest.

Kind regards,
Bart.

 

[BlueDun]

Ok, some english-german coticule translations first

In German "Belgischer Brocken" is used for both, a generic term for whetstones from the Ardennes as well as specifically for the yellow whetstone, the coticule that is. But usually, if used with no further specification, Belgischer Brocken (or "BB") refers to the yellow coticule.
If one wants to distinguish between the two, the Blue is called Blauer Belgischer Brocken ("BBB") and the coti is called Gelber Belgischer Brocken ("GBB"). As the article uses the acronym "BB" it most likely means the coti.
So "BB" in the text most likely is not the Blue Belgian Whetstone but rather Belgischer Brocken.

But anyway, your pictures and the varios readings lit up things to me: Spessartine comes in a a varieaty of slightly different chemical compositions. With these different compositions come different colors (nice pics btw, Bart). If I look at the first and the third picture above then I see pretty much the same as I see in the microscopic pictures. Red crystals in the blue and yellowish cristals in the coti. Evidence accepted and case closed. If we wanted to investigate further then we'd really need to go scientific.

Good idea to make a pass-around test package. If I fail in producing results then maybe the next in row will be more successful.

Cheers
BlueDun

 

[Bart]

You are correct. I misread BB for BBW. I didn't connect BB to Belgischer Brocken at all.

But indeed, that doesn't change the fact that I believe the scientific studies I've read and the people at Ardennes, who employ a qualified geologist, when they state that both stones have Spessartine Garnet as the main abrasive component.

As far as experimentation is concerned, I'll prepare a package. I'm going to include a fast BBW/Coticule combination and a slow Coticule, both from my small personal collection. I will also include slurry stones of La Veinette, La Petite Blanche and fast part of La Dressante. Those are currently the only determined slurry stones I have. When I've been to Ardennes over 3 weeks, I'll be able to send a few additional slurry stones. Sounds fine?

Kind regards,
Bart.

 

[BlueDun]

Bart, sounds like a plan :thumbup:

I would also start with a slow and a fast cutter as you suggest.
Have you got any evidence on how hardness and cutting speed correlates? In a first thought, one would assume that soft stones release more garnets thus are faster cutters. But this is only true under the assumption that a given amount of slurry will have the same cutting abilities no matter where it came from. If you allow for variations in the slurry's cutting abilty due to different garnet sizes, formation and concentration per volume of slurry then we have to consider this factor too (sometimes down the line after we made the first coarse steps).

Cheers
BlueDun

 

[Bart]

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All my experiences show that it doesn't correlates. I've seen hard Coticule that were among the fastest, soft Coticules that were among the slowest and vice versa.

I've replied to your e-mail as well. I'm going to need your address.

Kind regards,
Bart.

 

[Smythe]

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Indeed, I have a Coticule so soft you would think it was made of talc... and it's so slow you could do half strokes for hours and the slurry would still be milky white (forget setting bevels or removing scratch marks).

 

[Bart]

There was made reference earlier on in this thread about the look of Garnets. I am sharing a picture of a Coticule of a "Les Petas" layer. The image shows a cross-section of the hone, total width of view: 5mm. You can see a number of large spessartine garnets, noticeably red in the BBW part and white in the yellow part of the hone.

Best regards,
Bart.