Corning Museum of Glass

A glass, usually for wine and often of extraordinary shape, designed to be as difficult as possible to drink from without spilling the contents. In drinking competitions, any drinker who spilled wine was required to start again with a full glass.

The rainbowlike effect that changes according to the angle from which it is viewed or the angle of incidence of the source of light. On ancient glass, iridescence is caused by interference effects of light reflected from several layers of weathering products. On certain 19th- and 20th-century glasses, iridescence is a deliberate effect achieved by the introduction of metallic substances into the batch or by spraying the surface with stannous chloride or lead chloride and reheating it in a reducing atmosphere.