as I was creating some slurry last night it got me thinking...how much of the slurry created comes from the slurry stone? My stone has a thick layer of coticule, but I never want to waste any of it either.
Impossible to say. Anything in between 20 and 80%? Depending on the difference in hardness between the hone and the slurry stone.
It's important to know that when slurry is present, stroking with a razor not only abrades steel from the razor, but also abrades the surface of the hone, thereby releasing more slurry. That slurry obviously comes only from the Coticule.
It's rate to release fresh garnets plays a role in the speed of the hone.
Whether the rubbing stone has much influence on the honing process remains something that needs further research. I believe it does, but I have no idea at what extent.
I would assume the slurry comes from both during a honing session, maybe more from the rubbing stone at first, and later more added from the hone while honing, but the amount of slurry used to sharpen the blade is probably immeasurable compared to the total in the rubbing stone… mush less the hone itself.
These things last for generations, and I doubt one can use up the entire stone during a lifetime… unless honing a dozen razors a day and lapping frequently… I wouldn’t worry about it too much.
I'm forced to agree, and I've been using BBW/Coticules about 5 years, with no perceptible wear on the oldest coticule. However, the BBW side *does* show wear, albeit I used it on reprofiling a large D2 blade in an obsessive/compulsive marathon.. still, it does establish a baseline. One man with one razor will wear 1/4 inch of coticule in 240 years.
Assuming you're talking about the stone and slurry stone you got from me, the slurry stone seems to be a lot softer than the stone itself. So I imagine that most of the slurry crrated initially would be from the slurry stone. Then after some honing, as others have already said, the slurry would come from the hone itself from the honing action.
As an aside, I'm pretty sure that the slurry stone is from the La Petite Blanche layer, as it looks and performs just like a couple of La Petite Blanche stones I have. I mention that because it's a fast layer, so I think a slurry stone from a fast layer would speed up the honing process a lot, but that's just me supposing.