Tempered glass is about four times stronger than ordinary unfired glass. The large contraction of the inner layer during tempering causes compressive stresses on the glass surface that are balanced by tensile stresses in the glass body. The 6 mm thick fully toughened glass shall have a minimum surface compression of 69 MPa (10 000 psi). To be considered safety glass, the surface compressive stress must exceed 100 megapascals (15,000 psi). As a result of the increased surface pressure, when the glass is broken it becomes small rounded pieces (something like “rice”).
Thermally reinforced glass (SECURIT) focuses on its enormous resistance to breakage (400% more resistant than ordinary glass), essentially protecting against the adverse effects of the shattering of ordinary glass.
All the properties and most of the physical characteristics of the glass remain unchanged after heat treatment. Thus, the thermal conductivity, light reflection/permeability, energy absorption/reflection/permeability, surface expansion, elasticity index, sound insulation and weight remain the same.
However, some other characteristics are dramatically changed for the better, for example :
Impact resistance to deformable objects (human body) (+400%)
Tensile strength (+300% of ordinary glass)
Resistance to temperature differences (+500% of ordinary glass)
In summary, thermally toughened safety glass (which for the sake of brevity we will call roasted) has some special properties, in addition to those of ordinary glass:
They show 4 to 5 times increased mechanical strength, compared to the corresponding thickness of single glass panes.
If the breaking point is exceeded, then they are shattered into small pieces that are harmless to bodily integrity.
They exhibit very high resistance to temperature changes (up to 290°C), which makes them immune to thermal shocks (from non-artificial means).