Since its introduction by the British firm of Pilkington in 1959, the float process has become the world's principal method of flat glass manufacture.

In the float process, a continuous ribbon of glass up to 11 feet wide moves out of the melting furnace and floats along the surface of a bath of molten tin. The ribbon is held in a chemically controlled atmosphere at a high enough temperature for a long enough time for the irregularities to melt out and for the surfaces to become flat and parallel. Because the surface of the molten tin is absolutely flat, the glass also becomes flat.

The ribbon is then cooled down while still advancing across the molten tin until the surfaces are hard enough for it to progress through the annealing lehr without the rollers marking the bottom surface.

After annealing, the glass passes under water jets which stress the surface temporarily to help the cutting process farther along the line. Next, the glass is scored by cross cutters so that it can be snapped off into stock sizes farther down the line.

SOURCE
The Illustrated Science and Invention Encyclopedia New York: H.S. Stuttman Co., Inc., 1977

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This page was last updated on September 24, 2017.