Corning Museum of Glass

Glass that contains a high percentage of lead oxide (at least 20 percent of the batch). In modern times, glass of this type was patented in 1674 by George Ravenscroft (1632-1683), who added a larger amount of lead in 1676. Lead glass is relatively soft, and its refractive index gives a brilliance that may be exploited by covering the surface with polished wheel-cut facets. Such glass is often known by the term “lead crystal.”

An ancient Roman vessel decorated by undercutting so that the surface decoration stands free of the body of the glass, supported by struts. The vessel appears, therefore, to be enclosed in an openwork cage. Cage cups are sometimes known as diatreta or vasa diatreta.