Float glass is made in flat sheets and is an alternative name for annealed glass. It takes its name from the float tank used in its production, into which molten glass flows at around 1100 degrees C and on to a large mass of molten tin. Because the tin is much heavier than glass and its surface is smooth and flat, the glass forms a very uniform layer on top of the tin.
The float process has virtually eliminated other production methods such as sheet or plate glass manufacture. Sheet glass, including the machine-drawn cylinder process simulating hand-blown glass, was known for its wavy irregularities. Plate lass, first introduced into the UK in the mid-seventeenth century, was cast and then polished flat.
Tempered (toughened) glass is many times stronger than annealed glass. When broken, it shatters into many small fragments, which prevent major injuries. This type of glass is intended for glass façades, sliding doors, building entrances, bath and shower enclosures and other uses requiring superior strength and safety properties.
There are two different methods used to produce tempered glass: