What is glass??
Glass is a mixture of a number of metallic silicates, one of which is usually that of an alkali metal. It is a amorphous, transparent or translucent. It may also be considered as a solidified super cooled solution of various metallic silicates having infinite viscosity.
Glass has been extensively used in building construction since long for glazing doors, windows, , for insulation and for decoration purposes.
Rapid advances in glass technology
have opened up newer avenues for
its use in construction industry.
Types of Glass:
The most common types used in
building construction are sheet, plate,
laminated, insulating, tempered, wired and patterned glass (to control light).
Principle Constitutes of Glass:
The raw materials used in manufacturing glass are: sand, lime (chalks) and soda or potash which are fused over 1000°C. Oxides of iron, lead and borax are added to modify hardness, brilliance and colour. The functions of the various ingredients are as follows:
Silica: is used in the form of pure quartz, crushed sandstone and pulverised flint; should be free from iron contents for best quality glass. Since it melts at very high temperatures (1710°C)carbonates of sodium or potassium are added to lower down the fusing temperature to about 800°C. These also make liquid silica more viscous and workable.
Lime: is used in the form of limestone, chalk or pure marble and sometimes marl. The addition of lime makes the glass fluid and suitable for blowing, drawing, rolling, pressing or spinning. It also imparts durability and toughness to glass. Excess of lime makes the molten mass too thin for fabrication.
Soda: acts as an accelerator for the fusion of glass and excess of it is harmful.
Potash: It renders glass infusible and makes glass fire resistant.
Lead Oxide: imparts colour, brightness and shine. When 15–30% of it added to substitute lime it lowers the melting point, imparts good workability, while its transparency is lost with the glass becoming brittle and crystalline.
Cullet: It is broken glass of the type desired to be manufactured that is added to the raw materials to bring down cost of production.