Material Use

Silica sand, the main ingredient of glass, is mixed with lime and soda and heated to approximately 1,500°C using fossil fuels. The molten glass is passed over a bed of molten tin (at 1,000°C) and then cooled in a controlled manner to form a continuous sheet. Float glass is normally manufactured in thicknesses from 2–25 mm. Several other additives are put into the mix (magnesium and aluminium oxide) to help melting, and other oxides are added for colour. Float glass technology is continuing to develop with the refinement of the process to reduce energy use and byproducts.

Approximately 95 million metric tonnes of silica sand is mined each year, the majority of this in the United States. Float glass can be:

• polished
• toughened
• laminated
• coated
• tinted
• manufactured into components such as insulating glass units (IGUs, or double glazing).

These processes provide sheet glass with widely differing properties suitable for a wide variety of end uses. Recycled glass use is increasing, but specialist glasses are not recycled (for example, toughened or laminated).

See the Level factsheet on glass.