Cooper + Fire StatementCopper + Fire + Glass, sterling ear wires. I start the process with a glass compound consisting of quartz sand, iron oxide, potassium oxide, and borax, which together are colorless. Depending on the various metal oxides and chlorides a wide range of colors are created. I fire each piece to a precise temperature until the enamel melts and fills the space it's in, becoming shiny. The piece is taken out to cool, and then polished with a carborundum file.