Opal glass is normally used for lamps and decoration elements in interior design. Milky white, translucent, but not transparent, opal glass creates a very special atmosphere. Plates, bowls, cups and other tableware made of opal glass have a closed surface so that they are partcularly hygienic. Furthermore such series are particularly resistant to mechanical and thermal stress. As opal glass plates, bowls and cups are shock-resistant they are very popular in catering, canteens, industrial kitchens and in communal feeding in general, e.g. in hospitals.
In the past cryolite (sodium hexafluoroaluminate, formula: Na3AlF6) was used as opacifier for plates and other tableware. That's why it's also called cryolite glass. Nevertheless the opacity derives from sodium fluorite (NaF). Cryolite is a natural rescource, but nowadays the opacifier has a chemical structure.