Casting as in metal casting. Enamel as in "vitreous enamel" or "jewelry enamel." The term "enamel" has been largely debased by general use of any fired ceramic glaze (or in the case of "enamel paint" by anything vaguely hard and shiny) but good'n'proper enamel is ground glass fired to molten temperatures. In archetypal, respectable jewelry, it is always done over pure silver or gold. The artists most responsible for extending the art are all from the Art Nouveau period, notably Henri Vever, Rene Lalique and Peter Carl Faberge. Enameling itself has suffered mightily as the translucent, heavy metal enamels used in its creation are difficult to acquire compared to the garbage generally used. Not only that but wretched mass-production techniques have dissolved much of the market for actual jewelry enamel. But it's fun, it's easy, it's rewarding, it's meditative and it's repeatable. This took three hours.
