This bowl of sandwich gold-glass shows a fine floral design in gold leaf sandwiched between two layers of colourless (clear) glass.In order to fit together, the inner and outer bowls had to be made to an exact and predetermined shape and size. They were made by a hot process, which included slumping the glass into or over a ceramic hemispherical mould or form. This was rotated while a tool was used to work the soft glass downward. After cooling, the surfaces were then cold-worked. The gold foil decoration was stuck to the outer wall of the inner bowl, using an adhesive such as gum arabic mixed with water. Finally, the two glass bowls were fused together by placing the outer bowl into its original form (or a new one, if a positive form was initially used), before carefully lowering the inner bowl into it. The bowls were then heated together gradually in a kiln. At a certain temperature the glass softened slightly and the bowls fused together, though this did not happen uniformly throughout.A number of these remarkable sandwich gold glass bowls are known. This one, and three others, come from southern Italy, while others are known from the island of Rhodes, Gordion (modern Turkey) and Olbia on the Black Sea. One fragmentary example is decorated with a scene that suggests an Egyptian origin, but scenes of the River Nile were a popular theme in many parts of the ancient world. At this time many luxury goods were traded in all of these locations, and we have no clue as to where the sandwich gold glass was made. Their origin remains a mystery.