Abrasives in a Jewelry Context

Have you ever wondered about abrasives and how to use them? Here I'm going to give you the perspective of a jeweler working in brass, copper, silver, and gold. When you cut with a jeweler's saw, the marks left behind are coarse. How coarse? More coarse that 120 grit, but able to be removed by 120 grit abrasive. That's the trick all the way down to the bottom turtle. Each abrasive leaves marks. Each abrasive removes coarser marks. The idea is to remove EVERY coarser mark while leaving finer marks. (When I say 120 grit I also mean P120 which is a European standard.)

Here's a rule. If you want to remove a mark, you have to use a grit that is finer, but still close to the thing that left the mark. For example if you cut with a jeweler's saw and jump right away to a 1200 grit abrasive, you will only polish and shine the marks left by the saw. That's pretty useless, unless your aesthetic includes the brilliancy of polished saw marks. You will not be able to remove them with 1200 grit abrasives. Your only choice is to make them shinier and shinier until they have a mirror finish. The idea is that if you jump too many grades of grit, you won't be able to remove the marks you see in front of your face.

So what do you use? The idea is to double the grit each time to remove the marks of the grit before. To remove saw grits, use  120-180 grit. To remove those marks use 240 grit, then to remove those marks use 400-480 grit, then to remove those marks use 800-960 grit and then 1600-1920 grit. After that use a polish like rouge or Zam, or other polishing grits. Zam's abrasiveness is carefully tuned to polish silver without scratching turquoise, (i.e. it will actually remove scratches from turquoise and leave it polished without leaving any additional new marks but will bring silver/stainless silver to a fine polish). Rouge is finer and Green Rogue is yet finer.

I suppose that I should have an aside about stone hardness. In 1812, Frederick Mohs created a scale of hardness in minerals. Check out https://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness to learn more. 

The bottom line is that as the hardness of a mineral increases, you have to have a finer grit to polish a setting without scratching the mineral/jewel.

Most metal used in jewelry, i.e. silver and gold are between 2 mohs and 4 mohs in hardness.

Common dust includes a lot of quartz which is hardness 7 on the mohs scale. That means that ANY stone or metal with a hardness less that 7 will be scratched, day to day, by dust encountered in daily life in your pocket, your purse, or in your environment. So, sadly, your silver, your gold, or your turquoise, (mohs hardness of 4-6), will just get scratched all day. In a tumbler, you're looking for pre-polish grit, or about 500-600 grit polish for turquoise. There's no reason to go any coarser.

For more information on the polishes, check out https://blog.esslinger.com/guide-to-buffing-compounds-and-their-uses/