Toughened glass

Toughened safety glass (ESG) consists of a single, specially heat-treated glass. The glass is heated during processing to toughened safety glass to a temperature above its transformation temperature and then abruptly cooled down again. Here, the near-surface zones of the glass cool down faster than the inner core. The result will be a train in the core and in the surface compressive stress. ESG must therefore be ground or cut before heat treatment, subsequent processing is very limited. A processing which penetrates into the tensile stress of the glass would lead to rupture of the disc.

By the heat treatment, the glass has an increased shock and impact resistance compared to normal flat glass. This is demonstrated by means of the pendulum impact test according to DIN EN 12600. In addition, the toughened glass is insensitive to large differences in temperature. The thermal shock resistance is 200K.

If it breaks at high load, it breaks into small pieces. Thus, the risk of injury compared to normal flat glass is reduced considerably. ESG has been used for many decades in the automotive industry for side windows and effectively prevents cutting and impact injuries. The same service makes it in the house.

In addition to normal ESG, there are now almost exclusively so-called ESG -H. This toughened safety glass was subjected to the so-called heat-soak test or hot storage test. The glass like normal ESG is generated and then stored hot for several hours at a temperature of 280 to 300 degrees Celsius. This additional procedure greatly reduces the by nickel ( II ) sulfide inclusions caused, in practice, however, rarely occurring spontaneous fractures of normal ESG.