Someone asked me about a pendant she was having problems with, it tarnished in a fairly short time. She had sealed it with ProtectaClear, but the sterling tarnished anyway.
She told me about how she finished the metal. She had a very in-depth, complicated process she used on the sintered sterling metal clay. She cleaned it with water mixed with Dawn and ammonia, dried it, and then cleaned it with denatured alcohol and dried again on a coffee mug warmer. She then coated it once with ProtectaClear and accelerated drying with a low temp warmer.
There is no need to complete all of these processes. Jewelry manufacturers warn their customers not to use ammonia on sterling because it's not good for sterling. It causes sterling to turn black and other problems develop, then it will not clean by conventional methods. Scrubbing with Dawn, a detergent, leaves the detergent in the pores. My husband is a chemical engineer, he says detergents are stronger than soap and harder to remove from something porous. In theory, soaking the piece in denatured alcohol helps displace water, but it will not displace detergent or ammonia. The ammonia may have been the problem, especially if the pendant wasn't washed thoroughly.
I don't know if she dipped it in liver of sulfur before she did all of this. I have found that if a freshly sintered piece of metal clay is placed into liver of sulfur, the liver of sulfur is absorbed inside the porous areas of the piece. Over time it tends to oxidize faster, from the inside out. I suggest burnishing the pores closed using a steel or brass brush before applying liver of sulfur. After oxidizing, place the piece into a mixture of baking soda and water to neutralize the liver of sulfur. This keeps it from continuing the oxidation process. Then soak it in water, removing any other chemicals left behind. Dry completely and then polish. I personally don't use a lacquer over sterling silver. Over time the sterling silver still oxidizes, at which point, the lacquer must be removed in order to polish it.
Until next time, have fun claying around!
by Janet Alexander