Spontaneous Fracture in Thermally Strengthened Glass – a Review and Outlook

Thermal strengthening of glass is common for many different purposes including architecture, automotive, glasses for solar energy, tableware and occasionally also containers. It is an easy and relatively cheap method to make glasses stronger, however, with an Achilles heel that it can spontaneously fracture without the slightest applied external force. Though, fracture due to applied external force is the most common case, spontaneous fracture is rare. The current paper reviews the literature of spontaneous fracture and NiS inclusions and what kind of mitigation measures that have been done in order to reduce the frequency of spontaneous fracture. Finally is also an outlook for the alternative mitigation measures and their advantages as well as disadvantages. A personal perspective is given in discussions and gives an outlook to the most promising alternative methods to reduce and hopefully eliminate the NiS inclusions. These include multi-functional methods where not only the NiS inclusion issue is solved.