There are many ways to finish your Precious Metal Clay pieces, but I like to use Liver of Sulphur the best. I am going to tell you how I like to finish my pieces with Liver of Sulphur and how I have learned to control the results I get. My favorite look for my finished Precious Metal Clay pieces is an antiqued kind of rough style. I also like the color range I can get with the Liver of Sulphur finish.
When I first learned how to use Liver of Sulphur, I was taught to take my somewhat cleaned piece of Precious Metal Clay and just drop it into a bowl of Liver of Sulphur and let it sit there. Then I polished the piece in a tumbler.
When I started experimenting with finishes, I realized that that method really limited the results that I could get with Liver of Sulphur. When I dropped the PMC piece in to a bowl of Liver of Sulphur, the result was that they piece usually turned black. And even if it didn’t, when I polished it in a tumbler afterward, the piece turned black and shiny.
What I do now is different. First, I polish and clean my pieces in a tumbler. I usually will tumble pieces for at least a few hours in a dishwashing soap and water mix, using mixed stainless steel shot. You can use any brand of liquid dishwashing soap.
Second, I use dry Liver of Sulphur pieces dropped into cool water. Remember, that if your Liver of Sulphur solution is warm, it changes the color faster. I want it to change slowly, so that I have more control over the result. I typically use a plastic fork to put my Precious Metal Clay piece on and dip the PMC in and out of the Liver of Sulphur solution. I can dip all or part of the Precious Metal Clay into the Liver of Sulphur.
Once I achieve the color I want, I rinse the Precious Metal Clay off quickly in a waiting bowl of plain water. This stops the color from changing any more. By doing it this way, I can get finishes from pale yellow, to copper, to red, to blue, to purple, all the way to black. Much more interesting than the previous method.
If you are looking for a copy of Introduction to Precious Metal Clay by Mary Ann Devos, I highly recommend getting it from this seller on eBay because they are selling it at a very good price. It is a good book to have in your PMC library.