Evolution of lead-free crystal

- May 12, 2020-

Around the 16th century, Italian craftsmen began to dig and use natural crystals. Due to their high hardness and low reserves, it was difficult to make them into utensils. By the end of the 17th century, Italian glass manufacturers invented artificial crystal, also known as crystal glass, by adding a certain percentage of lead to the quartz sand solution. Artificial crystal not only overcomes the above-mentioned deficiencies of natural crystal, but also has high transparency, good refractive performance, thick, and cut-resistant, which is easy to be carved and carved. Therefore, it has become an important milestone in the history of glass development and ushered in the heyday of Italian glass.

At the time, crystal was widely used in crystal chandeliers and various lightings, and it almost became an indispensable decoration for churches, conference venues, hotels, and high-end residences. (In Europe at the time, this was a high-end luxury and a symbol of identity.) Wine, water, tableware, lamps, trophies, developed into imitation jewelry, jewelry, fashion, shoes, hats, watches, as well as furniture, building components, etc .; from household utensils, decorations, displays, art to high Technology products are almost all-encompassing. Swarovski is the application of crystal in jewelry.

In China, during the Warring States period, Chu people have used quartz sand, galena, and barite as raw materials to make decorative glasses such as sword heads and jade. However, these glasses are translucent or opaque dark glass. There is a clear difference between lead crystal glass.

After the Western Han Dynasty, the composition of glass made in China was changed from the composition of lead barium silicate to the composition of lead glass, making glass with better light transmittance. Ancient literature believed that the appearance of glass at this time was similar to crystal or jade, which replaced jade. Effect, but from a physical point of view, these glasses cannot be called lead crystal glass.

Lead glass developed in China in the 1950s, mainly flint glass of optical glass, was used as optical material. In the 1960s, lead glass for radiation protection was developed. It was only in the 1970s that Dalian, Shanghai and other utensil factories developed the true medium lead (lead oxide> 24%) and high lead (lead oxide> 30%) crystal glass.

The pollution of lead in crystal glass has been attracting attention. In 1976, the World Health Organization noticed the dissolution of lead in glass and ceramics. The US Food and Drug Administration regulated the dissolution of lead and cadmium in ceramic glaze. The International Organization for Standardization clearly stipulates that when the volume is greater than 600 ml, the allowable limit of lead dissolution is 2.5 mg / L. In 1991, the European and American International Crystal Union made stricter regulations than ISO. Under the same conditions, the allowable limit of lead dissolution is 1.5 mg / L.

The Canadian Safety Commission has made recommendations on the safety of the use of lead crystals. It is believed that the daily intake of lead should not be greater than 5 micrograms per deciliter. When lead crystal glass is filled with wine, the amount of lead dissolved can reach 1-500 micrograms / liter It is recommended not to store acidic liquids in lead crystal bottles.

The European Parliament and the Council stipulated that from July 1, 2007, the content of harmful substances such as lead, mercury and cadmium in circuits and electronic equipment shall be prohibited from 10-9 levels, but the lead crystal glass shall be temporarily put on hold.

In recent years, domestic traditional glassware factories have basically not produced lead crystal glass. From the perspective of development trends, lead-free crystal glass is imperative. In the 1850s, the Soviet Union, the Czech Republic and other Eastern European countries have been conducting research on lead-free crystals. From the 1980s to the 1990s, some western countries have also published patents for lead-free crystals.