Toughened glass is also known as tempered glass. Toughened glass is produced by first cutting and processing sheets of glass, which are then loaded into a furnace that has a bed of oscillating rollers.
The glass is heated to a plastic state at around 650ºC, and then by computer control, the glass is moved into the quench area where it is rapidly cooled by a series of high pressure air nozzles.
This rapid cooling or quenching induces high compression stress in the glass surface, while the centre remains in tension. Although the physical characteristics remain unchanged, the additional stresses created within the glass increases its thermal and mechanical strength.
Metro have multiple furnaces across their manufacturing sites in Auckland, Tauranga, Wellington and Christchurch, with the Auckland Furnace capable of toughening panel’s up to 5.1x2.4m