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All crystal is glass, but not all glass is crystal, as the Etched Crystals website explains. To be called crystal, glass must contain a percentage of lead, but the definition of crystal and its various types differs among different countries.
Glass Composition
Glass is made using three minerals: sand (silica), soda ash (sodium carbonate) and limestone (calcium carbonate). The application of intense heat changes the sand into a fragile form of glass. Soda ash is added to the mixture to lower the melting temperature of the sand, and limestone is added to make the glass stronger. The materials are then melted together in a furnace at 2,912 degrees Fahrenheit to produce glass. This is the same temperature produced in a jet engine, according to Etched Crystals.
Crystal Glass
According to the European legal definition, glass must contain at least 24 percent lead oxide to be called "full lead crystal." Glass itself is not a crystal, since cooled glass only has one amorphous structure giving it shape, whereas the molecules of crystal are arranged in a precisely defined crystalline structure, as the Foci Glass, Minnesota Center for Glass Arts website explains. The term "lead crystal" for crystal glass derives from the Venetian use of the word "cristallo" for the rock crystal imitated by Murano glassmakers. Cristallo, a pure, thin, colorless glass formulated on Murano between 1450 and 1460, was possibly the most significant creation to come from the Venetian glass industry, according to the Foci Glass website.
Significance
Crystal glassware is valued for its beauty, and its distinctive cut patterns and their gorgeous sparkle are due to its lead content. The lead makes the crystal softer than glass, enabling it to be cut. It also has a high index of refraction, which is what creates the brilliant sparkle of crystal that is cut at sharp angles.
Glass-Crystal Spectrum
Different definitions of crystal hold in different countries. In Europe, a glass item with lead content of more than 4 percent but less than 10 percent is usually called glass, while an item with lead content of between 8 and 10 percent is usually called lead glass. Lead content between 10 and 30 percent is required for the item to be called crystal, and if the lead content is higher, it is called lead crystal. In the United States, however, glass is classified as crystal if it has a lead content of 1 percent, according to the Etched Crystals website.
Considerations
Although lead content is often considered a sign of glass quality, the European Commission website reports it is increasingly a source of consumer concern, because the lead in crystal glassware can leach into acidic beverages. Small- and medium-sized enterprises from a number of European countries completed a research project in late 1997 to investigate safe alternatives to the use of lead in glass crystal, with worker safety a particular concern. The study found that the alternative metals were safe for workers and consumers, and that the products made in this way were virtually indistinguishable from the highest-quality crystal lead products, according to the European Commission website. The study did not confirm that the new type of crystal glass could be cut and polished in the same way as lead crystal, however.
Glass Composition
Glass is made using three minerals: sand (silica), soda ash (sodium carbonate) and limestone (calcium carbonate). The application of intense heat changes the sand into a fragile form of glass. Soda ash is added to the mixture to lower the melting temperature of the sand, and limestone is added to make the glass stronger. The materials are then melted together in a furnace at 2,912 degrees Fahrenheit to produce glass. This is the same temperature produced in a jet engine, according to Etched Crystals.
Crystal Glass
According to the European legal definition, glass must contain at least 24 percent lead oxide to be called "full lead crystal." Glass itself is not a crystal, since cooled glass only has one amorphous structure giving it shape, whereas the molecules of crystal are arranged in a precisely defined crystalline structure, as the Foci Glass, Minnesota Center for Glass Arts website explains. The term "lead crystal" for crystal glass derives from the Venetian use of the word "cristallo" for the rock crystal imitated by Murano glassmakers. Cristallo, a pure, thin, colorless glass formulated on Murano between 1450 and 1460, was possibly the most significant creation to come from the Venetian glass industry, according to the Foci Glass website.
Significance
Crystal glassware is valued for its beauty, and its distinctive cut patterns and their gorgeous sparkle are due to its lead content. The lead makes the crystal softer than glass, enabling it to be cut. It also has a high index of refraction, which is what creates the brilliant sparkle of crystal that is cut at sharp angles.
Glass-Crystal Spectrum
Different definitions of crystal hold in different countries. In Europe, a glass item with lead content of more than 4 percent but less than 10 percent is usually called glass, while an item with lead content of between 8 and 10 percent is usually called lead glass. Lead content between 10 and 30 percent is required for the item to be called crystal, and if the lead content is higher, it is called lead crystal. In the United States, however, glass is classified as crystal if it has a lead content of 1 percent, according to the Etched Crystals website.
Considerations
Although lead content is often considered a sign of glass quality, the European Commission website reports it is increasingly a source of consumer concern, because the lead in crystal glassware can leach into acidic beverages. Small- and medium-sized enterprises from a number of European countries completed a research project in late 1997 to investigate safe alternatives to the use of lead in glass crystal, with worker safety a particular concern. The study found that the alternative metals were safe for workers and consumers, and that the products made in this way were virtually indistinguishable from the highest-quality crystal lead products, according to the European Commission website. The study did not confirm that the new type of crystal glass could be cut and polished in the same way as lead crystal, however.
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