Thread: belgium blue

The garnets in the BBW have been reported as being slightly larger in size than those in the coticule (see Bart's thread on Blues and Yellows in the Advanced Honing forum, last paragraph). This may explain the difference in 'grit' between the two.

Unfortunately, "they" were simply going by what they see and experience. The truth of the matter is that with natural hones, it's impossible to say that a blue hone is this and a yellow hone is that... Nature made those hones, and Nature isn't big on quality control..... or carefully checking the ingredients before making honing stones. The Coticules are particularly difficult to catagorize as the garnet crystals as so different from other abrasive crystals in the way they cut and behave. However, your point that there are generally fewer crystals in the blue vs yellow is correct and I seem to recall that the crystal size might be slightly larger in the blue but again, you can't tell for sure as this can vary from sample to sample. What you are forgetting to take into account is the binder in the blue vs yellow rock. The actual sediment that binds the rock together also has a profound effect on it's honing ability even though it does not do any honing itself. Yellow coticules in particular seem to vary more than the Blue in this regard, some being soft, others hard and many more somewhere in between. Soft binders will allow a slurry to develop quicker, allows the garnets to protrude more from the substrate by wearing away quicker and allows dull garnets to be shed faster which all promotes faster honing. A harder substrate would retain the crystals, keeping the tops closer to the surface and retain them longer, allowing them to round over more before being torn loose. That would result in a slower cutting, smoother polishing hone than the first one.

Manufacturers use the same tricks when making hones and grinding wheels. The harder the steel you are trying to grind, the softer the binder in the grinding wheel, which allows the grit to shed before it dulls too far and simply creates friction that heats the steel rather than cut it. That's why machine shops use white wheels (or pink, or blue... ) to cut high speed tool steels but welding shops stick to those hard, tough grey wheels that grind soft steel just fine but need to be dressed with a diamond point to refresh the surface and remove the embedded swarf.


Regards

Christian

Well good explanation but all a bit confusing for me. how would i no my yellow is a good polishing hone i would say when i rub with slurry stone it does create a slurry but not as quick as i would of thought .

Originally Posted by gary haywood

The other thing i can't understand is they say blue is a 4k and yellow is 8k.The way i see it is there both the same except the yellow produces more garnets which makes it a faster cutter? and blue less which makes it a slower cutter so surley you could start on yellow and finish on the blue and it is the garnets that do the cutting in the slurry may be some one can explain?

Gary, the quantity of garnets is linked with the numbering 4K and 8K.

BBW: 4K grit (=4000 grit), so there are approx. 4000 garnets in one square inch BBW surface

Coticule: 8K (=8000 grit), so there are approx. 8000 garnets in one square inch Coticule surface

The more garnets there are in one square inch surface the smaller they are. So a Coticule garnet is smaller then a BBW garnet.
The smaller the garnets the faster you can sharpen your razor.

Side note --> the use of a slurry stone gives us 2 advantages: 1. it creates more slurry on the surface of your honing stone & 2. the garnets in the surface of both your honing stone and slurry stone are rubbed together. This way the garnets will be smaller then when not using a slurry stone.


@ kaptain_zero

Very nice explanation!

Thanks for that info good explanation but you'd think a 4k would cut quicker than an 8k that is the case with the norton if you need to remove more metal you'd use a lower grit and polish with higher grit. I should get my bbw tomorrow morning i will try it before my yellow and finish with yellow and see what happens.

Originally Posted by gary haywood

Well good explanation but all a bit confusing for me. how would i no my yellow is a good polishing hone i would say when i rub with slurry stone it does create a slurry but not as quick as i would of thought .

If you want to use your Coticule as a finishing hone, than don't worry about slurry. According to a booklet, written some 30 years ago (in French) about Coticule, fast and soft coticules were used to form the edge. Next they went to a harder coticule for finishing the edge.
As long as your coticule isn't so soft that it produces slurry on it's own, your coticule will finish just fine with water only. Raising slurry is for fast steel removal. Run a perfectly honed razor for 10 laps on a coticule with slurry and test shave. You'll know instantly why it is not recommended as a finisher in that mode.
For use as a finisher, I've really never found much difference between the Coticules I've tried. The differences really emerge when you raise a slurry on them, and then we're primarily taking about speed of steel removal.

Hey Rob, I was unaware that the Belgian hones contain 4000 and 8000 garnets per square inch.
Thanks for sharing that.
But either way, I'm still no big fan of designating a grit rating for natural Belgian hones. People often start believing that they can interchange the Blue/Yellow with the Norton4K/8K, while they are in fact pretty incomparable.

BART I WOULD LIKE TO USE MY BBW/ COTICULE TO REFRESH AND MAINTAIN MY RAZOR I SHOULD IMAGINE THAT WOULD BE POSSIBLE WOULD'NT IT. MY YELLOW DOES'NT RAZE A SLURRY ON ITS OWN I DO HAVE TO USE A SLURRY STONE TO DO SO AND I HAVE HONED A GOODISH RAZOR WITH A SLURRY AND YOUR RIGHT IT DID DETERIATE THE EDGE SLIGHTLY SO I DID 100 LAPS WITH WATER AND THIS DID UNDO THAT AND THE RAZOR AFTER STROPPING DID SHAVE WELL. SO WOULD I BE RIGHT IN SAYING IF PLAIN WATER DID'NT TOUCH UP MY EDGE THEN I SHOULD START WITH SLURRY AND FINISH WITH PLAIN WATER.

Originally Posted by gary haywood

BART I WOULD LIKE TO USE MY BBW/ COTICULE TO REFRESH AND MAINTAIN MY RAZOR I SHOULD IMAGINE THAT WOULD BE POSSIBLE WOULD'NT IT. MY YELLOW DOES'NT RAZE A SLURRY ON ITS OWN I DO HAVE TO USE A SLURRY STONE TO DO SO AND I HAVE HONED A GOODISH RAZOR WITH A SLURRY AND YOUR RIGHT IT DID DETERIATE THE EDGE SLIGHTLY SO I DID 100 LAPS WITH WATER AND THIS DID UNDO THAT AND THE RAZOR AFTER STROPPING DID SHAVE WELL. SO WOULD I BE RIGHT IN SAYING IF PLAIN WATER DID'NT TOUCH UP MY EDGE THEN I SHOULD START WITH SLURRY AND FINISH WITH PLAIN WATER.

Gary, no need to shout so loud, my friend (in case you don't know, capitals mean you are shouting)

Yes, I think maintaining a razor is very possible with a Blue and a Coticule.
During the first 6 months of my...eh... honing career (if I may call it that way) I really wanted to hone with slurry on my coticule. For some odd twist in my mind, I thought I was not making full use of the hone's capacity, if I used it without slurry. It bothered me that every time I used slurry during the final stages of my honing attempts, I seemed to loose sharpness instead of gaining it. I have tried finishing with slurry on (opens drawer and starts counting) 11 different Coticules. I have honed backwards on slurry, I added layers of tape to the spine before a few final passes on slurry, I transfered slurry to a paddle strop (no kidding), I used thick slurry, thin slurry, dry slurry, slurry on top of a DMT1200. Not one single time I got a great shaving edge. The only exception is when I gradually wash away the slurry with drops of water as I go along. It's a fun method actually, and you never know up front if you're gonna get an awesome edge or just a decent one.
If you are pleased with an edge left by honing on a Coticule with slurry and then 100 laps with water, than you are going to be thrilled when you take a razor with a good bevel for 50 laps to a Blue with a thin slurry and next finish with 100 laps on a Coticule with water only. That, or you have a Coticule like I never encountered one.
But either way, I may hone on stone, but I don't write on stone. In the end all that matters is that you and I are happy shavers. I just like to share my experiences, in the hope that someone might benefit from it. It's never my intention to start a new religion, so if you do things differently, I'm always keen on learning something new myself.

Best regards,
Bart.

Right now I have four coticules. Two are naturals. Two of them came from Howard, one directly from Ardennes, and one is a vintage piece. The natural from The Perfect Edge is one of the most outstanding stones I have encountered. The blue side cuts like a Norton 4K and the yellow side with water only is also a fast cutter. FWIW, the yellow side has what looks almost like a spider web of purple throughout it's surface so that may account for it's performance.

The Kosher from Ardennes is a pure finisher. It is as one would expect from that grade uniform in color and a very slow cutter. My tiger striped coticule from Howard is a slow cutter. It is good with slurry and then following with water only but I'm not crazy about the performance. Beautiful stone though.

The vintage natural came from Tony Miller. The blue side is alright and the yellow side is very good. I need to do some more work with it for a proper evaluation but so far the natural from Perfect Edge is the top performer of the four. Just more grist for the mill.

Many thanks to Christian, Bart and Rob for the informative posts on the coticule.

Originally Posted by gary haywood

Thanks for that info good explanation but you'd think a 4k would cut quicker than an 8k that is the case with the norton if you need to remove more metal you'd use a lower grit and polish with higher grit. I should get my bbw tomorrow morning i will try it before my yellow and finish with yellow and see what happens.

You have to understand that there's a difference between 1. removing an amount of metal and 2. creating a sharp edge.

Case 1. : lower grit --> less garnets in 1 square inch surface --> bigger garnets because there are less garnets in the surface (15 to 20 micron for the BBW)

Case 2. : higher grit --> more garnets in 1 square inch surface --> smaller garnets (+/- 5 micron for a Coticule)

So in case 1 you can say that you are removing a lot of metal when honing your knife/razor. But removing a lot of metal isn't the same as creating a sharp edge! Because the garnets are bigger then in case 2 it's difficult to create an edge that's as sharp as in case 2.

In case 2 you can also say that you are removing a lot of metal because you have a lot more garnets (more garnets but smaller garnets) then in case 1. And because you have smaller garnets then in case 1 you can create a much sharper edge then in case 1.

I hope this clears things up for you!
If not, shoot your questions!

-Rob