Lead crystal
Lead crystal is a term for smooth or polished lead glass. The term " lead crystal " is misleading, as it is, so is an amorphous solid is not a crystal, but a glass.
It is a silica sand, potash and red lead () made jewelry glass and is often used as a gemstone for imitation rhinestones.
Lead crystal is also a synonym for high-quality utensils made of lead glass, especially drinking glasses for wine and sparkling wine, decanters, candlesticks, bowls, boxes, vases and cake plates. Furthermore, jewelery and decorative items such as busts, miniature models, crystal pendants of chandeliers, etc., made of lead crystal.
To produce colored lead crystal, there are two methods. The better method is to paint the glasses with special colors, which remain connected by a subsequent burning process permanently to the glass.
High quality colored lead crystal glasses are produced in the so-called overlay technique. Here, the transparent glass is coated during manufacture with different colored liquid glass and then shaped. The partial grinding away the colored outer surface after cooling arise colorful glass structures. Such glasses are often handmade and priced accordingly.
Lead crystal is traditionally produced in the territory of the Bohemian forest massif, ie the border between Bavaria and the Czech Republic. It was invented in the Jizera Mountains, where it is still made in factories. On the German side, the centers of the lead crystal production are located in the Bavarian Forest and the Upper Palatinate Forest. The reason for the concentration in these forest mountains can be seen next to the quartz deposits that it here wood for the required high wood consumption in glass manufacture was, in particular for the production of potash ( see Bavarian pile ).
In Germany Lead crystal is now made industrially by the glass is mechanically pressed or blown into a mold. This already formed the typical shape of the glass and the grinding process is omitted. The surface is then etched in hydrofluoric acid, one refers to the acid polishing. For smooth cut without glasses even cheaper and more environmentally friendly fire polishing is used, which glasses are smoothed by uniformly heating the surface.
Health
Lead is harmful to human health and it is in principle possible that lead crystal glasses give off small amounts of lead in the food stored therein. Whether this occurs in significant amounts, probably depends mainly on the quality of the lenses, so the accuracy of the production process and the nature of the substance from ( eg temperature, pH, solvent concentration ), which comes into contact with the glass. Therefore, the competent authorities shall periodically products made of lead crystal on the solubility of the lead contained therein, most samples give no health-relevant amounts of lead.