How does polish work?

I think the general consensus is that it works more like your first proposal- just super fine grit that leaves nearly invisible scratches, but some researchers have indicated that there could be something else going on at the molecular level.

It clearly is not a "coating" like nail polish, which is a comparatively thick coating of a foreign substance, but some have hinted that silica molecules may be getting pulled out of the host rock to form an infinitesimally thin layer that is the "shine".

I expect a person could do their PhD on the subject and still not have a definitive answer.

Good article from Lapidary Journal on the subject;

www.lapidaryjournal.com/feature/nov05.cfm


and it is written by a PhD, like I said he doesn't have "the" answer, although it is considerably better documented and more authoritative than any of our ramblings here...

For what it's worth, I believe polish works just by making the imperfections on the rock surface so fine and the surface so smooth that the rocks "shines". I think it is an abrasive process. You can see the effect with a 10X loupe. If you remove stones at various times through the polish stage, you can watch the imperfections in the stones surface become finer and finer, and the stone become shinier and shinier. I use a loupe to determine when the rocks are truly "done". To me, it is when the imperfections are no longer visible in a 10X loupe, which means they are 10X finer than your eye can detect. I suppose if you used a 20X or 30X loupe you could follow the polish process even further, though I don't know if you could actually remove the imperfections seen under 30X magnification. In practical terms, even when the "scratches" are gone under a 10X loupe there are other imperfections visible, such as fine cracks or fine pits or blemishes that you can never remove.

People usually refer to finer grits and polishes removing "scratches" from the previous stages. Seen under magnification, they aren't actually scratches, more like just an uneven surface, or millions of tiny pits side by side. Each successive grit makes the pits a bit smaller. The polish stage is no different I think. Well, one difference is that polishes like aluminum oxide tend to become rounded, like little ball-bearings, which helps smooth the surface, as opposed to silicon carbide grit which fractures into jagged pieces as it breaks down, which keep on cutting. Aluminum oxide has a mohs hardness of 9.0, so it is harder than almost any rock you will be polishing (which are generally mohs 7 or softer). My two cents.
-Don

Thanks for the post Rally!

And I agree with Don's view of the "scratches" as actually being pits. I've looked at them under a loupe, too and they look like a matte surface, or sort of like a golf ball. The pits get smaller as you go.

Chuck

The Bielby, surface-flow theory is easily debunked, the tumbling or grinding process does not produce the temperatures required to melt the material... thousands of degrees. Pretty easy to prove at home.

Seems pretty simple to me that finer grits produce finer scratches, with the flour-sized particles of polish rendering scratches too fine for our eyes to see.

Faceters do see some curious things, but perhaps much can be explained by either unscientific testing ore the atomic structure of crystalline solids, that behave nothing like glass.