The Float Process
At the heart of the world's glass industry is the float process - invented by Sir Alastair Pilkington in 1952 - which manufactures clear, tinted and coated glass for buildings, and clear and tinted glass for vehicles. The process, originally able to make only 6mm thick glass, now makes it as thin as 0.4 mm and as thick as 25 mm. Molten glass, at approximately 1000°C, is poured continuously from a furnace onto a shallow bath of molten tin. It floats on the tin, spreads out and forms a level surface. Thickness is controlled by the speed at which solidifying glass ribbon is drawn off from the bath. After annealing (controlled cooling) the glass emerges as a 'fire' polished product with virtually parallel surfaces.
A float plant, which operates non-stop for between 10-15 years, makes around 6000 kilometres of glass a year in thicknesses of 0.4 mm to 25 mm and in widths up to 3 metres. The float process has been licensed to more than 40 manufacturers in 30 countries. Around 370 float lines are in operation, under construction or planned worldwide with a combined output of about 970,000 tonnes of glass a week. The NSG Group operates or has interests in 51 float lines worldwide.