Glass production takes place in several main steps: melting the raw materials, shaping them into a product, controlled cooling and finishing. Depending on the intended application, different techniques are combined.
Application
The process begins with melting the raw materials, mainly quartz sand, soda and lime, in a furnace at around 1500 °C. This creates a viscous glass mass that is free of air bubbles and impurities.
The mass is then shaped. For flat glass, the float method is most common: the molten glass is poured onto a bath of molten tin, where it spontaneously takes on a uniform thickness and a flat, smooth surface. Other classic methods are drawing glass into sheets or tubes, rolling it between rollers for patterned or wired glass, and blowing hollow objects such as bottles and decorative glass.
After shaping comes cooling, or annealing. Glass must cool slowly and in a controlled way in an annealing oven, so that internal stresses are relieved that would otherwise make the glass brittle and prone to breaking.
The glass can then be processed further. Through thermal or chemical tempering, toughened safety glass is produced that is stronger and breaks into small, harmless pieces. In laminated glass, several sheets of glass are bonded with a tough interlayer. Finally, the glass is cut to size, ground and finished, and where required processed into insulating double glazing.
Related terms
- glass
- building glass
- double glazing
- quartz
- lime
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