Glass production involves two main methods: the float glass process that produces sheet glass, and glassblowing that produces bottles and other containers. For this post, we would be discussing the float glass process.
Float Glass Process
The float glass manufacturing process was developed by Pilkington in 1959, taking flat glass technology to a revolutionary new level. The glass gains its lustrous finish and perfect flatness by floating on a bath of molten tin in a chemically controlled atmosphere. The ribbon of glass is then cooled, while still moving, until the surfaces are hard enough for it to be taken out of the bath without the roller marking the surface. The glass is then automatically cut and stacked, ready to be packed for distribution to local and international customers. Below are the stages of float glass processing:
1) Sand, limestone, soda ash, dolomite, iron oxide and salt cake are mixed together with cullet in the batch plant.
2) The raw materials are then charged into a large furnace to be melted at 1600°C. They combine in a process of physical transformation to form molten glass.
3) A continuous ribbon of molten glass is fed out of the melting furnace onto the surface of an enclosed bath of molten tin at 1100°C. The molten glass literally floats on top of the tin, and as it flows along the surface of the tin bath away from the delivery canal, it forms a ribbon of uniform thickness. Thickness is controlled by the speed at which solidifying glass ribbon is drawn off from the bath.
4) The glass is then lifted from the tin bath onto rollers to the annealing lehr to be cooled down. At this stage the internal stresses are released ensuring perfect flatness and solidity.
5) Once cooled down and solidified the glass goes to the cutting area where it is cut in to a large sheet of ‘jumbo size’ (6×3.21 meters) or ‘cut-size’ which are specific to customer orders, before being stacked for transportation.