Composition And Manufacture
Ordinary glass used in building is also known as soda-lime-silicate glass and has the following composition:
- silica, the raw material, in the form of sand (70 to 75 %), up to 28% of this constituent may be cullet, or waste glass.
- soda, the flux, as carbonate and sulphate (approximately 12 – 14 %)
- lime, a stabiliser, in the form of limestone (approximately 5 – 12 %)
- various other oxides such as alumina and magnesia, to improve the physical properties of the glass, including its resistance to atmospheric pollutants.
- for body-tinted glasses, metal oxides can also be incorporated.
Batch house (1)
Float glass manufacture consists of three main stages:
- melting, when the raw materials become molten at a temperature of around 1500 – 1800 °C
- refinement, when the molten glass is homogenised and gas bubbles are removed
- temperature control, when the molten glass is cooled to a point where its viscosity is suitable for drawing into the tin float bath.