bugbear":3adr09w6 said:
D_W":3adr09w6 said:
What's the "jasper" stone? Not one I've seen listed in the older sources I have.
The only Jasper I know is a highly variable, semi-precious stone, with no abrasive properties I'm aware of.
EDIT; found it (and you, I'm guessing, DaveW
)
http://straightrazorplace.com/hones/111 ... -jade.html
That's some obsessive stuff, there.
BugBear
Without a diamond hone, jasper will cut softer steels and do some cutting on water hardening tool steels, but not much (which makes it a good wire edge chaser). It's about 10 bucks over here in thin slabs that are used by jewelers (someone working as a faceter turned us on to it).
If you scuff it up with a diamond hone and make a slurry of it's own particles, it's really aggressive and not as fine until it settles in again. REALLY aggressive.
Unfortunately, the one that I used for that test was a new piece with some mill marks in it, so it can go a bit finer. It's interesting to see how fine the scratches are from the japanese stone, jasper and agate. And interesting in the shave to find out what edges look like (the little bits of flotsam on the edge before stropping with the jasper are thin foil that look bad, but don't seem to affect a shade - they are orders smaller than anything that would show up on wood).
Safe to say, the only practical use of a jasper in woodworking or knife sharpening is as a burnisher, other stones are better on slurry and the jaspers are REALLY hard. Some steels are so soft (440a stainless type steels, etc in pocket knives) that they won't take a good edge on anything other than fine compounds....or the jasper. It's useful in those cases to burnish and consolidate an edge. And on wharncliffe type blades where it's easy to use, it's a nice follow on to an arkansas stone and very fast to use before bare leather.
The chinese agate stone is similar in role, a little different in feel. A waste of money for anything other than razors (and really, a waste of money when jasper can be had for a few bucks). The advent of diamond plates has made it so that you can get some stones that won't release particles to release particles and cut, and do it without contamination that would occur if you tried to use emery. It's made things like ultra hard japanese stones popular for razors whereas 100 years ago, the stones that were a touch softer were preferred.
I have a little problem with sharpening stones and sharpening materials. (I still use a washita in woodworking tools, the nutty stuff is razor related where you can get a great edge and actually keep it for months, as opposed to a few plane strokes).
(I just read one of the posts, I'll wait for the critics to point out that I used the term coplanar where I should've said planar).