Glass is created by melting a mixture of quartz sand, soda and lime at high temperature into a clear, hard substance. Each ingredient performs its own function.
Application
The main raw material of glass is quartz sand, which consists of about seventy percent silicon dioxide (silica). Pure quartz sand forms the glass network, the basic structure of the material. However, quartz sand only melts at a very high temperature, around 1700 °C, which makes producing glass from sand alone costly and energy-intensive.
To lower the melting point, soda (sodium carbonate) is added. Soda acts as a flux: it lowers the required temperature to about 1500 °C, making the process more practical and economical. A drawback is that glass made from sand and soda alone would be water-soluble.
For this reason, lime (calcium carbonate, or quicklime) is added as a stabiliser. Lime makes the glass chemically resistant and durable, so it is not attacked by water. This mixture of silica, soda and lime forms the basis of common soda-lime glass.
In addition, smaller amounts of additives are often used, such as metal oxides for colouring or decolouring, and cullet from recycled glass that eases melting. When the mixture melts in a furnace at around 1500 °C, a viscous mass forms that can be shaped into glass.
Related terms
- glass
- building glass
- quartz
- lime
- double glazing
Learn more about building terms in our knowledge base at fredsdiyplans.com.