Float glass as a material is one of the most highly manufactured and used types of glass. The term 'Float' is derived from from the production method, introduced in the UK by Sir Alastair Pilkington in the late 1950's, and this method is responsible for 90% of todays manufactured flat glass. Previous to Pilkington's method, all flat glass was hand blown into cylinders and slumping was used to make them into flat sheets.
When float glass is manufactured the raw materials (silica sand, calcium, oxide, soda and magnesium) are mixed and then introduces into a furnace where they are melted at 1500° C. The molten glass then flows from the glass furnace into a bath of molten tim in a continuous ribbon. The glass, which is highly viscous, and the tin, which is very fluid, do not mix and the contact surface between the two materials is perfectly flat. When it leaves the bath of molten tint he glass has cooled down suficiently to pass through an annealing chamber called a lher. Here it is cooled at controlled temperatures, until it is essentially at room temperature.1
top view of the process of making float glass
Float glass process.
1. Glass on Web, 'Float Glass', March 2007. http://www.glassonweb.com/glassmanual/topics/index/float.htm (accessed October, 2010)
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