Glass Manufacturing - Raw Materials and Cost Structure
Glass is obtained by the fusion of several inorganic substances. The fused mass is cooled to ambient temperature at a rate fast enough to prevent crystallisation, i.e., the molecules cannot arrange themselves into a crystalline pattern. The fast rate of cooling to prevent crystallisation applies to transparent glasses.
Raw Materials and Costs of Flat Glass
- The mix of raw materials used in the production of flat glass is known as the batch, which is mainly composed of three components: silica sand, soda ash and dolomite/limestone.
- Recycled glass (cullet) is used in the fabrication of flat glass and represents on average 15 per cent of the materials used. Its addition helps reduce the energy required in the process.
- Silica sand, soda ash, dolomite and dolomite/limestone represent together 99 per cent of all raw materials used in the production of glass, excluding recycled glass. The remaining ingredients aid the melting and refining (bubble removal) reactions and impart colour and there is water addition during batch mixing to prevent subsequent segregation.
- Silica sand is the main component of the batch as it constitutes about 62 per cent of the batch weight excluding recycled glass. Soda ash is one of the most expensive raw materials used in glass manufacturing and represents about 16 per cent of the batch weight but about 60 per cent of the batch cost. In terms of costs, raw materials and energy are the single largest elements, followed by overheads and prime labour.
