Single layer toughened safety glass is heat soaked, tempered glass. During processing to toughened glass, the base glass is heated to about 600 °C and then cooled abruptly. By blowing cooling air the areas of the glass near the surface cool faster than the inner core. As a result, tension is formed in the core and a compressive stress on the surface.
Through heat treatment (soaking), the glass has an increased impact and knock resistance compared to non pre-stressed base glass and is less sensitive to large temperature differences.
If it breaks under high stress, it crumbles into blunt-edged, loosely connected pieces.
Heat soaked single layer toughened safety glass
Each base glass has marginal small amounts of unavoidable nickel sulphide crystals. These have no effect. However, the strong cooling processes in the production of toughened glass act on the NiS particles. The crystals are highly supercooled. With subsequent heat sources, such as solar radiation, the crystal structure may change as the volume increases and lead to spontaneous breakage.
For applications that are exposed to high temperature fluctuations, we recommend a supplementary heat soak test after finishing.
In this test, the toughened glass is stored in accordance with DIN EN 14179 at a temperature of about 280° C to 300° C for several hours. Any spontaneous fractures caused are thereby controlled.