leaded glass

Lead glass, commonly called crystal, is a subcategory of glass in which lead replaces the calcium content of a typical potash glass. There are three primary criteria that must be met in order for lead glass to be given the name crystal, as was established by the European Union in 1969: Lead content higher than 24%, density higher than 2.90, and a reflective index of 1.545. If the lead glass does not meet these criteria, it will sometimes be referred to as crystallin or crystal glass.
In nature, crystals form naturally using crystallization; their molecules are arranged in an ordered pattern, and the patterns extend in all three spatial dimensions. Although lead glass appears as a more pure form of glass, it is not formed in this way and is not a naturally forming crystal. While somewhat inappropriately named, crystal has remained the popular term for any glassware that is more elegant, more intricately designed and faceted, and with higher density.
Lead crystal used to be found more often in the construction of glassware and windows, but due to the poisonous properties of the chemical, it has become a less popular alternative. However, if used in an ordinary way, crystal is perfectly safe to drink from. If there is concern about the lead leaching into the liquid inside, filling the glass or bottle with white vinegar, and letting it sit for 24 hours, will allow the majority of the leached lead molecules to be drawn into the acidic solution; as a result, the surface layers of the glass will be practically lead free. Many manufacturers employ this practice as well, but even without this, the levels of lead received by drinking from a lead crystal glass are less than during normal food consumption. It is not suggested that liquids that are going to be consumed be stored for long periods of time be kept in lead crystal, but for 2-3 hours it is perfectly safe.

Some manufacturers have created a lead-free crystal. In this type of glass, the lead oxide has been replaced with other materials such as zinc oxide, potassium oxide, or barium oxide. These materials have similar properties, without the stigma the word lead brings with it. The manufacturers of lead-free crystal explain that while adding lead to glass originally added a component of clarity and density, our technology is such now that the lead is no longer adding anything to the appearance or drinking experience, and could be replaced with alternatives that are ultimately safer and easier to form into elegant designs.

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