What Is The Float Glass Process?

By Deb Levy


The Float Glass Process is used to make high-quality, flat glass for the construction and automotive industry. Developed in 1959, this highly-technical manufacturing process involves using some of earth’s most abundant raw materials to produce a durable glass product. The main ingredients in glass are:

- Silica Sand: Makes up 60% of glass

- Limestone: Contributes strength properties to glass

- Soda Ash: Helps glass endure a range of temperatures without melting

- Dolomite: Contributes to glass’ resistance to melting

- Glass Cullet: Commonly known as ‘broken glass’; this accelerates the melting of glass as it goes through the float glass process.

In the float glass process, a continuous strip of molten glass, heated to more than 1000 degrees Centigrade is poured from a furnace on to a large shallow bath of molten metal, usually tin.

The glass floats and cools on the tin and spreads out to form a flat surface. The speed at which the controlling glass ribbon is drawn determines the thickness of the glass. The glass is now perfectly flat and parallel.

Rollers are used across the top of the glass, pulling or stretching it out to achieve a thinner finished product.

The Cooling Process Explained

As the glass continues through the process, it begins its cooling down phase. To complete this, the temperature is slowly cooled from 1100 degrees Fahrenheit to 200 degrees. This temperature change is accomplished in the length of approximately 800 feet.

After the glass is cooled, it is trimmed down and any excess glass removed. These glass remains are re-used as glass cullet in later batches.

To learn more about the Glass Float Process, view the video below.

You can learn more about the process in the video below.

Here are some examples of the float glass process in action:

From Guardian

From Pilkington

From PPG Industries