Thread: Grit of a yellow coticule

Originally Posted by thebigspendur

You have to remember that synthetic hones are manmade from ceramic particales that are uniform and then they are cemented together. Diamond hones are industrial grade diamonds sorted by size and or crushed to uniform size and cemented to a manmade substrate As a result they are all the same and give uniform results. Natural hones are just pieces of rock. Now let me put my geology background to work here. A mineral is a homogenious substance like quartz or calcite or sapphire while a rock is a collection of minerals like granite or basalt. A Hone is a rock so its a collection of minerals. The ones we are concerned with are the mineral garnets that are mixed into the matrix and do the cutting. Now a hone stone has to be very special. If the garnets are too big they won't do anything. If they are too small they won't do anything. If the matrix is too friable and it falls apart too easily it won't do anything and if its too hard it will not work properly. Also there are many different varieties of garnets. There are iron rich ones, calcium rich ones, magnesium rich ones, chromium rich ones and on and on so the type of garnet has to be the right one too. Some are harder than others. Also the xtls can vary from cubes to 12 sides dodecahedrons so all this has to be right also.So all these variables have to be just right. Since its natural stuff as you go from quarry to quarry and quarry face to quarry face the vein with the stuff we all want changes as its mined out.

So the point is that from week to week and sometimes day to day the product will be different and have different cutting characteristics so you just have to rely on the seller and his suppliers to obtain consistant stock. So depending on where you obtained you hone from the coticule might be closer to 8K or closer to 10K or closer to 12K. It can all vary. You really can't compare different stones from different locales. So if you want a Coticule that's say 10K you need to find a reliable supplier who can supply that type of stone for you.

Clear as mud?

Actually, it makes perfect sense to me. Thanks for the lesson, it's much appreciated.

As some of you already know I've recently acquired 2 Belgian coticule stones, one on eBay, and the other in a local junk store. Both seem very old.

The "yellow" side of one of the stones is a rich, yellow, mustard, cream, tan color, while the other is a little paler shade of that yellow mustard, cream, tan color.

I'm not sure if they are backed with slate or another Belgian "Blue", stone, as the stone seem to be hard and doesn't have the appearance of slate.

The "alternate" side on one of the stones has a thick rich purple, blue color, while the "alternate" side on the other stone also has purple, and blue, side but with more blue/grey and less purple... both seem to have some kind of grit also...

The "grit" on the "blue/purple" sides of these stones seem larger than the "grit" and more aggressive than the "grit" the yellow sides...

I read from posts on this forum that the grit on the yellow side can be anything from less than 6K all the way up to 10K, and everything in between, and the "blue/purple side can be anything from 1K to 4K... is there any CHEAP & PRACTICAL way for me to determine the grits size of the particulate in my stones?

I'd appreciate any assistance in helping me determine exactly what my stones are and how to best use them ...

Thanks in advance,

Tony

The Norton 8k is not equivalent to the coticule 8k. The coticule 8k is much finer and more like a 10k or 12k (that's just an estimate with no scientific proof) relative to the Norton. Different companies don't use an industry standard K rating as there is none. There is supposed to be a standard grit rating but I've found that to be somewhat subjective as well. To understand why someone would go from a Norton 8k to a coticule, you have to try it and then shave. You will definitely feel the difference and I know this not only from my own experience but from the excited phone calls I get from customers.

Originally Posted by Howard

The Norton 8k is not equivalent to the coticule 8k. The coticule 8k is much finer and more like a 10k or 12k (that's just an estimate with no scientific proof) relative to the Norton. Different companies don't use an industry standard K rating as there is none. There is supposed to be a standard grit rating but I've found that to be somewhat subjective as well. To understand why someone would go from a Norton 8k to a coticule, you have to try it and then shave. You will definitely feel the difference and I know this not only from my own experience but from the excited phone calls I get from customers.

Howard:

thanks much for the information. It sounds like a natural coticule would be superior in its results compared to a man made stone. In your estimation would it be OK to go from a norton 4k to a yellow coticule or is the 8k norton still a good intermediate step?

I appreciate everyone's feedback on this thread. It has given me a much better understanding of the coticule's place and value in a sharpening system.

From what I've read here on SRP, the whole concept of grit rating is only useful to a certain point. This comes up with the barber hones, too. The hone can have bigger particles that make shallower grooves--in other words, a hone can be "coarser" but still produce a nice polish on an edge. Grit size is a handy reference, though, and for newbies the "shave with it" response isn't always super helpful.

Maybe the old-timers were on to something when they just referred to hones as coarse, medium and fine. The consensus is that a coticule is finer than a Norton 8K; how much finer depends on the stone and the skill of the user.

Just musing,
Josh