Chemical toughening

Glass with a thickness of less than 3 mm generally undergoes chemical toughening to achieve increased strength. This process also creates a compressive pressure zone on the glass surface which takes place through ion exchange in a bath of molten salt between the glass surfaces and the salt bath. This involves, for example, sodium ions being replaced by potassium ions. Because potassium ions are around 30% larger than sodium ions, a compressive pressure zone forms on the glass surface. The extent of this compressive pressure zone depends on the type of glass and the tempering parameters being used.

The mechanical strength of anti-reflective glass from SCHOTT with optical interference coatings (e.g. CONTURAN®) can also be significantly increased using this process.