When a piece of floating glass is placed on top of a piece of molten metal, the final product is called float glass. This process creates a uniform piece of glass that is entirely solid. Most contemporary residential and industrial buildings are made from float glass, though this wasn't always the case.
Before the dawn of the 17th century, almost all glass panels were cut from crown glass. In order to manufacture crown glass, glass manufacturers had to create large cylinder shapes that were then cut in half and flattened to form one window pane. In 1848, an English engineer by the name of Henry Bessemer attempted to form a glass manufacturing process that was less tedious than the original crown glass process. Bessemer's manufacturing system included one large ribbon of flat glass that was rolled between two rollers.
In addition to the rolling of the glass, each pane of glass had to be polished by hand. This turned out to be a very costly manufacturing process. Numerous inventors attempted to create a more efficient system, though none succeeded. It was not until the early 1950s that Alastair Pilkington and Kenneth Bickerstaff invented a new kind of glass termed float glass.
Float glass is derived from a mixture of raw materials including sand, limestone, dolomite, and soda ash. These materials are mixed together, and then placed into an extremely hot furnace. Once the glass has reached the desired temperature, it is stabilized, and then placed inside of a molten tin bath. Due to the reaction between the glass and the molten tin, the glass eventually makes its way to the surface of the tin bath. As soon as the glass is cool enough to handle, it is passed through two mechanical rollers.
The speed of the rolling machine indicates the width and size of the glass, which is why some pieces of float glass are larger or smaller than others. Finally, the glass is placed into a lehr kiln, a temperature controlled kiln that is specially made for the glass process. The result of this entire procedure is a perfectly smooth piece of uniform glass.
As soon as a piece of glass is stable temperature-wise, it is then cut into specific shapes and patterns according to a customer's needs. Within the glass world, the float glass process is frequently referred to as the Pilkington process, since Alastair Pilkington is largely credited with the invention of float glass.