Figured coticule = hard coticule?

Maybe this is an obvious thing to others that I've overlooked before, but I'm looking for experiences of others with their coticules. Howard or Bart, your opinion would really be appreciated.

I recently purchased from forum member Memorael a figured coticule that is extremely hard. It is both a fast cutter and top-notch polisher/finisher, a pretty great combination.

It occured to me that I have about 3 or 4 coticules that have figure or grain in their surface, and without exception they are the hardest coticules I have. The other coticules I have all have a plain or creamy surface. None of the plain ones are as hard as the coticules with figure, and a few are very soft, generating slurry during simple honing with no slurry stone.

Below is a photo to help illustrate what I mean. What I'm calling a "figured" coticule is on the left, and a "plain" coticule is on the right. The stone on the left is a natural I bought from Howard over a year ago (my very first coticule). It is extremely hard, good polisher, fast cutter with slurry. On the right is a kosher natural I bought from forum member Memorael a while back. It is the softest coticule I have, and is plain. Both are great, for different reasons.

Am I off base here? Anybody have a soft coticule with figure, or a hard polisher coticule that is plain? Is the presence of figure actually a reliable signature for relative coticule hardness?

http://i76.photobucket.com/albums/j2...Comparison.jpg

I have found a similar trend, but I only have two coticules (one of each sort).

My coticule is like the one on the right. It dosnt generate much if any slurry with razors but does flatten easaly. So I'm guessing softer. The BBW side has the same figuring as the one on the left and is very hard.

I have found exactly the same thing. I have had three coticules (I sold one -- a bout -- that was like a petite blanche), one is very yellow without any figuring. It is quite soft and cuts fast. The other is just like yours on the left, kind of looks like tiger striping a little bit, and it's much harder.

scott.

Bart is the best person to guide you on this.

I've had quit athew coticules i never had one that generates a slurry by just honing i have some that cut averge with slurry and a couple that cut fast and very fast but they all finish equaly the same as for soft and hard i tend to feel when in use with water some can feel softer and some can feel glassier. I have a coti bout from bart and it cuts so quik its unbaleivable actualy bart tested it for me i brought it from rob at ardenees this one is a standard which cost much less and it does agreat job

I have been assessing Coticules, with the idea of figuring these kind of things out.
But I have not nearly collected enough data to confirm or negate the premise that a "grainy" look, can predict anything about a Coticule's properties.

As you may know, Coticules are harvested from different layers, which all carry a unique name. Some layers seem (based on my limited group of tested specimens) to deliver more "grainy" looking Coticules than others, which seem to deliver more evenly looking hones. "La Grise" and "La Grosse Jaune" seem to yield grainy looking hones.

So far in my investigations, two Layers have turned out to show, each on his own, little variance. "La Petite Blanche' (delivers almost exclusively very pale, texture-free Cotcules) and "La Veinette" ( a wider variety of appearance, but very invariable quality nevertheless)

Other layers, notably "La Dressante" have shown a wide variety of morphological variance. They also show significant differences in speed and behavior, but so far, I have found no correlations between appearance and capabilities.

As far as hardness is concerned, I have no idea how to measure that. It is a fact that a Coticule, when used with slurry, needs to abrade itself at a slow but steady pace, in order to release a continuous stream of fresh garnets.
Yet, garnets have a hardness of 7.5 on the Mohs scale. The phylosilicates that bind them together are all significantly softer than that, and they surely don't need to be as soft as a fingernail to give the whetstone excellent cutting speed. I do find differences in speed between Coticules, but nothing I can predict by looking at the hone or scratching it with my fingernail. In general, differences in size (stroke length) will often contribute more to honing speed than the peculiarities of the Coticule.

When it comes to the final edges that are possible, I have find only very marginal, almost indiscernible differences, on all Coticules I have tested so far. Each hone gets used with three different methods and the resulting edges are submitted to a comparative test shave. Only the amount of work to get a fully refined edge varies.

Best regards,
Bart.

Thanks for your detailed explanation, Bart.