Thread: South African Hones....

Originally Posted by mainaman

Coticules have spherical grit particles, Jnatas and Thuri/Escher are flakes not even remote resembpance to sphere, they are wide and not very thick.

Right, thus the comment "if they are that nicely shaped". It's easier to talk about the size of the particles if the discussion is simplified. The surfaces of most hard stones look like stacked dandruff under a microscope.

a quality Jnat will be hard enough to not release slurry on its own. Releasing slurry is not good because it will mix with the worked slurry and mess up the refinement of the bevel. To overcome the hardness fo the stone one uses a softer slurry stone.

Exactly my point. I'm not aware of a good finish stone that is natural and that does release grit at any appreciable rate. If the particles were 1/10th the size that they are, it wouldn't be such a big deal. But there aren't any that are that small. Most natural stones that are hard and that have uniform reasonably small particles will make a good finisher if they hold their grit. It's hard to draw a line for a certain stone at an equivalent synthetic grit unless some sort of control is used (e.g., a certain exact amount of pressure is used on every single stone). Once you're working with a surface of a stone that is burnished to some extent, you can not necessarily create a finer edge with a stone that has 4 micron particles than one with 6 or 8, it depends on how they work worn in, and how you work with the stone. If the particles are similar shaped, and without regarding hardness, if a slurry is made, the larger particles will likely leave a coarser pattern.

But since we're trying to grade a finish stone based on what it's capable of, it's not really based on particle size within a relative range. Thus, my only real question is how hard is it bound together, how fast does it break in and will it still polish the work done by a slurry once it's broken in. Some super super hard stones still have to be conditioned a little bit from time to time as they are even slow to polish.