The metal is usually copper or, though rarely, brass. Sometimes also golden jewelry are enameled.
The process starts with the copper piece being glazed with kaolinite three times and baked in furnace when a white, smooth layer settles on. Then the glaze is painted by hand. The paint usually comes from different oxides.
After the painting is done, the piece is again baked in furnace. Here the oxide used and the furnace temperature render the final color of the painting.