Denis Chénard, Orléans, Ont.
>"It goes both ways. If man-made abrasives are better, and they produce a better edge while leaving the bevel "shiny", then there should be a scientific explanation as to why this is the case. Anything less doesn't cut the mustard IMHO. (That physics Ph.D. makes me cranky sometimes.)"

Granted. The hypothesis here that man-made abrasives used in the stones are of uniform (or close to) size, thus they abrade the steel in a consistent manner. Go fine enough, and the surface becomes so flat as to reflect light. If the back and bevel can become that flat, then their junction should be as sharp as possible.

OTOH, the more dispersed particulate size of a natural stone creates a random scratch pattern, which disperses light because of the less flat surface. Again these scratches on both bevel and back, when they meet at the edge, should make for a less sharp edge. Frank says that his observations contradict this.

The only way that I could explain this paradox it that the bevel and back, in contact with the stone, do indeed produce a rougher surface. But the slurry, being made of broken down particles, becomes finer and finer as we go, and it would be the slurry that does refine the edge. The bevel (or back), being in contact with new particles from the stone, can't get shiny because it's in contact with fresh particles of "random" size.

Does that make kind of sense?

DC

No Ph.D (dropped out at the thesis stage), but I did start in physics in university (long story).