Lead glass, commonly called crystal, is a variety of glass in which lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40% (by mass) lead(II) oxide (PbO), while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO. Lead glass is often desirable for a variety of uses due to its clarity. In marketing terms it is often called crystal glass.
The term lead crystal is, technically, not an accurate term to describe lead glass, because glass lacks a crystalline structure and is instead an amorphous solid. The use of the term lead crystal remains popular for historical and commercial reasons, and sometimes simply crystal because "lead" seems toxic to consumers. It is retained from the Venetian word cristallo to describe the rock crystal (quartz) imitated by Murano glassmakers. This naming convention has been maintained to the present day to describe decorative hollow-ware.
Lead crystal glassware was formerly used to store and serve drinks, but due to the health risks of lead, this has become rare. One alternative material is modern crystal glass, in which barium oxide, zinc oxide, or potassium oxide are employed instead of lead oxide.
In the European Union, labeling of "crystal" products is regulated by Council Directive 69/493/EEC, which defines four categories, depending on the chemical composition and properties of the material. Only glass products containing at least 24% of lead oxide may be referred to as "lead crystal". Products with less lead oxide, or glass products with other metal oxides used in place of lead oxide, must be labeled "crystalline" or "crystal glass".
The addition of lead oxide to glass raises its refractive index and lowers its working temperature and viscosity. The attractive optical properties of lead glass result from the high content of the heavy metal lead. The high atomic number of lead also raises the density of the material, since lead has a very high atomic weight of 207.
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Murano is a series of islands linked by bridges in the Venetian Lagoon, northern Italy. It lies about north of Venice and measures about across with a population of just over 5,000 (2004 figures). It is famous for its glass making. It was once an independent comune, but is now a frazione of the comune of Venice. Murano was initially settled by the Romans and from the sixth century by people from Altinum and Oderzo. At first, the island prospered as a fishing port and through its production of salt.
Venetian glass (vetro veneziano) is glassware made in Venice, typically on the island of Murano near the city. Traditionally it is made with a soda–lime "metal" and is typically elaborately decorated, with various "hot" glass-forming techniques, as well as gilding, enamel, or engraving. Production has been concentrated on the Venetian island of Murano since the 13th century. Today Murano is known for its art glass, but it has a long history of innovations in glassmaking in addition to its artistic fame—and was Europe's major center for luxury glass from the High Middle Ages to the Italian Renaissance.
A chandelier (ˌʃændəˈlɪər; also known as girandole, candelabra lamp, or least commonly suspended lights) is a branched ornamental light fixture designed to be mounted on ceilings or walls. Chandeliers are often ornate, and normally use incandescent light bulbs, though some modern designs also use fluorescent lamps and recently LEDs. Classic chandeliers have arrays of hanging crystal prisms to illuminate a room with refracted light, while contemporary chandeliers assume a more minimalist design that does not contain prisms and illuminate a room with direct light from the lamps, sometimes also equipped with translucent glass covering each lamp.
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