Finishing your fired Precious Metal Clay piece
Once you have cooled off your piece after firing PMC, it is time to decide how you want to finish it. In this post, I am going to discuss how to polish the piece with the assumption that you want a matte or shiny finish, but no oxidation.
After firing PMC in a kiln, it has a white or gray crust on the outside. That is normal, so don't worry about how it looks. The crust is the leftover binder that came to the surface as your PMC piece bonded together in the kiln.
There are a few ways to remove the crust, depending on how you want the piece to look after it is completed.
If you want a matte finish, you can take a wire brush, most people like brass brushes, and brush the crust off until you have the look you want. Then you can take a cloth to slowly bring up shine to the piece until you are satisfied. Remember that since PMC is 995 silver it is fairly soft as metals go, so you don't want to use anything too harsh on the surface.
If you want a shiny finish, you can start with the method above and continue to buff the piece with polishing cloths, fine grit sandpaper, or microfiber polishing paper to get a hand buffed shiny finish, or you can use my personal favorite method, drop the entire piece into a tumbler and let the machine polish it for you.
Tumblers are much faster, and they will also harden the silver as they polish it, so this is one of the reasons that I like to use them. You can use a small tumbler to polish an entire kiln full of PMC. I use a mixed stainless steel shot and a few drops of dish soap, and water in my tumbler, and the PMC always comes out great.
You can find loads of great tumblers on eBay or you can buy them from any lapidary or jewelry supplies distributor. The most important thing is that you need stainless steel shot to put inside your tumbler. Stainless steel shot will not rust, and it will polish your metal pieces.
Here is a link to eBay to buy a tumbler.