Chemical hardening is mostly applied for the solidification of thin glasses with a thickness of up to 3 mm. Chemical pretensioning is recommended because the surface flatness can be maintained. Producers of copy machines, solar modules, microwave devices, measuring instruments as well as companies in the lighting industry, the automotive industry and other users of flat glass need to apply the toughest possible glass in their products. Nearly all glasses containing a large percentage of sodium can be strengthened by means of ion exchange.