Toughened glass, or tempered glass is obtained by heating the glass at a temperature of up to 700-740 Cº, then quickly cooling its surface: in this way, the glass becomes five times as strong, while preserving its flexibility.
Thanks to this process, should toughened glass break, it crumbles into small granular chunks, thus reducing the risk of injury.
The essential factor in reducing the probability of glass sheets breaking during the tempering process is careful glass edge processing. It is widely acknowledged that the edgework quality can affect both the quality and the mechanical features of the final product.
Toughened glass is used for glass walls, double glazing or laminated windows, etc. mainly applications that require the following:
- greater resistance to mechanical shocks (glass doors, glass panels with point fixings such as glass balustrades, etc.)
- increased thermal stress resistance (glass panels exposed to intense sunlight or placed near heat, as in glass cladding, etc.)
- a type of breakage that reduces the risk of injury
There is still a risk that thermally toughened glass may accidentally break or spontaneously break without external pressure. It is therefore recommended to submit tempered glass to an additional thermal treatment called HEAT-SOAK TREATMENT.
Nickel sulfide (NiS) inclusions usually present in any type of glass, increase their volume at high temperatures. Thus, the balance of pressures inside the tempered glass can be affected, leading to so called "spontaneous breakage". According to the type of application in which the tempered glass is to be used "heat-soak" treatment may be used to reduce the risk of human injury.
Thus, once it has been toughened, the glass is placed in a furnace at a constant temperature of approximately 290°C for about 4-8 hours. This is intended to cause glass containing nickel sulfide inclusions to break in the heat-soak chamber, thus reducing the risk of potential breakage in the field.
The tempering technology complies with European Standards EN 12150 and EN 1863, which regulate the processing of float glass with thicknesses between 4 to 19 mm and sizes of 4800x2400 mm and of special glass like reflexive or Low-E glass. TRANSPARENT DESIGN bought from GLASTON (in 2016) a new tempering furnace RC 200 VORTEX PLUS. In the RC 200, the heater system combines the lengthwise heaters with GLASTON VORTEX PLUS a unique convection system that provides uniform heat transfer and ensures good control of the heating process. Both these features have a significant impact on the furnace output in terms of both capacity and quality (plane and spotless glass). The GLASTON VORTEX convection system provides the best control of glass heating in its class and enables us to have great results not only for float clear glass but also for low –iron and Low-e ( e =0.04/0.02) glass production.