What is the deal with sterling silver and copper turning black?
That is firescale and it is copper to blame. That black coating is basically a result of heating copper in the presence of oxygen, and can be removed by filing and sanding. We don’t recommend firing sterling at higher temperatures, like 800°C, or torch firing, because the firescale may prevent a good bond with sterling, which may cause problems. Depending on handling, sterling may become significantly weaker when fired.
