CrystalCrystal, or full crystal, is a glass that has greater than 24% lead-oxide (PbO) according to a European council directive established in 1969†. This is a heavy glass with a high refractive index and high dispersion of light. As such, it is traditionally valued for its clarity, weight and sparkly appearance. Crystal is commonly used to make glassware and ornamental items with dramatic cut facets that accentuate the prism-like properties of the glass. Lead glass has high viscosity meaning that it can be worked at low temperatures. This allows manufacturers to produce particularly decorative and elaborate designs with this material.
Lead is toxic, particularly to the brain. The use of lead in a wide range of products has been banned or regulated in many countries. To date, crystal glass has mostly escaped such regulations due to its association with tradition, culture and the luxury goods industry that has created resistance to change amongst manufacturers and consumers. In fact, there are government supported standards in place that require manufacturers to put at least 24% lead in products to call it crystal. In other words, standards require the use of high lead content as opposed to restricting it.
Rock CrystalCrystal glass is named for rock crystals such as quartz that have a similar appearance and weight. Glass has been named after crystal since at least the 13th century and may have originated with Venetian glass produced in Murano known as cristallo. Glass is amorphous and doesn't have a crystalline structure. As such, calling glass a crystal is something of a misnomer that is accepted due to long established traditions. Ornamental items may be made from real rock crystal such as quartz but these materials aren't particularly suited to hollowware such as glasses.
Crystalline & Crystal GlassAccording to the European standards of 1969, the trade terms crystalline and crystal glass refer to any product made from any combination of zinc oxide, lead oxide, barium oxide or potassium oxide†. The standard further specifies that these combined have a weight greater than 10%. These products may have similar optical properties to crystal but will always weigh less as lead is amongst the heaviest and most dense metals. Consumers commonly perceive crystalline and crystal glass as being lead-free. However, this is not necessarily the case as these products can contain more than 10% lead oxide according to the standard. It is common for manufacturers to state a product is crystalline or crystal glass without any disclosure of what materials they contain.
Lead-free CrystallineManufacturers may explicitly state that their products are lead-free crystalline meaning that they are made from alternatives such as zinc oxide, barium oxide or potassium oxide. These have the advantage of having very similar properties to traditional crystal while being relatively less toxic. Glasses made with titanium dioxide and zirconium dioxide also have similar properties to crystal. It can't be assumed that crystalline is lead-free unless it is specifically labeled as such and this has been certified by a reputable organization.
Leaded GlassLeaded glass is also used in ceramic glazes, vitreous enamels, optical glasses and for industrial purposes such as radiation shielding. As with glass products, it can be difficult to tell if ceramicware contains lead unless it is specifically labeled and certified as lead-free by the manufacturer.
|Overview: Crystal Glass
A tradition term for glass with high lead content.
A category of glass that is valued for its weight and optical properties that is made by substituting the calcium in regular soda-lime glass with some combination of lead oxide, zinc oxide, barium oxide, potassium oxide, titanium dioxide or zirconium dioxide.