Tumbling Oxidized Metal
Have you ever had a problem with tumbling oxidized metal? Is it better to tumble it dry — copper, for example? If I oxidize it to black and tumble it, will the oxidation come off with soapy water? Also, will it leave residue in the shot that will ruin a future batch of Sterling silver?
I've never had a problem tumbling oxidized metal nor have I had a problem mixing metals such as copper and silver together. I've been using the two together in my jewelry designs for years and love the look! I think adding a few pieces of silver to the copper makes the piece look richer and more expensive.
I have never tumbled any metals dry....the rotary tumblers are designed to use Stainless steel shot, water and a squirt of liquid dish soap. My preference is the original Dawn® dish soap. When I want a darker patina, I let the item dry completely before tumbling and then only tumble for 1-2 hours tops. Tumble longer and the patina could start to be removed by the tumbling action. I seal the finish with a clear lacquer enamel.
As to the residue on the shot, I clean my shot and barrel with dish-soapy water and rinse before re-loading the barrel. This prevents any build-up of unwanted crud in my tumbler. This morning, I tumbled some bright silver earrings after an evening of tumbling some heavily oxidized bracelets with no problems. They turned out shiny and beautiful with a bright finish. Of course, the shot, etc. had been cleaned before I added the new items. :)
I DO tumble silver and copper together and I oxidize them together too. Both turn out beautifully but there are some rules to be observed when oxidizing the metals together. I've heard it said that this could not be successfully done, and that is absolutely not true. You just remember the metallurgy of each and treat them accordingly.