Vitreous enamel, also called porcelain enamel, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C (1,380 and 1,560 °F). The powder melts, flows, and then hardens to a smooth, durable vitreous coating. The word comes from the Latin vitreum, meaning "glass". Enamel was used in Iran for colouring and ornamenting the surface of metals by fusing over it brilliant colours that are decorated in an intricate design and called it Meenakari. The French traveler, Jean Chardin, who toured Iran during the Safavid period, made a reference to an enamel work of Isfahan, which comprised a pattern of birds and animals on a floral background in light blue, green, yellow, and red. Gold has been used traditionally for Meenakari jewelry as it holds the enamel better, lasts longer and its luster brings out the colors of the enamels. Silver, a later introduction, is used for artifacts like boxes, bowls, spoons, and art pieces while Copper which is used for handicraft products was introduced only after the Gold Control Act, which compelled the Meenakars to look for a material other than gold, was enforced in India. Initially, the work of Meenakari often went unnoticed as this art was traditionally used as a backing for the famous Kundan or stone-studded jewelry. This also allowed the wearer to reverse the jewelry as also promised a special joy in the secret of the hidden design.