How Glass Is Made: A Brief History


Have you ever wondered how glass is made? Glass has come a long way from its earliest known uses in the prehistoric era when naturally occurring pieces of glass, which were found near volcanoes and lightning strikes, were shaped to form weapons and other items like beads for jewellery.

The discovery of glassblowing in the first century revolutionized the glass industry. The process was adopted and quickly spread throughout the Roman Empire. Adding  manganese dioxide to the process produced a clear glass. With clear glass now possible, glass windows started being used in architectural designs. Glass as we primarily know it today first made an appearance as windows in the luxury homes and villas in Rome and Pompeii.

In the 11th century, the technique was modified further. A glassblower would spin molten glass at the end of a pole, shaping it into a flat disc. This disc was then cut into panes for use in windows. Pigment could also be added to create stained-glass windows.

How Glass is Made: Pilkington’s Float Process

Today, Cornwall Glass uses glass manufactured in a six-step process called the ‘Float.’ Invented only 70 years ago by Sir Alastair Pilkington in 1952, the float process involves pouring molten glass (heated to over 1000 degrees centigrade) over molten tin. The molten glass floats on the tin and forms a flat, level surface. A limitation of the original process was that the sheets produced were only 6mm thick. Thickness is determined by the speed at which the hardening glass product is removed from the molten tin. Rollers are used to pull and stretch it. Once the glass is cooled (from 1000 degrees down to 200 degrees), the sheet or pane of glass can be cut and trimmed.

Today, the thickness of glass can vary from 0.4mm up to 25mm, which is a big step forward from the single 6mm option from 1952! Around the world, about 370 float plants produce on average 970,000 tonnes of glass product each week! Float plants can also operate non-stop for up to 15 years and make about 6000 kms of product each year!

Glass has definitely come a long way since its prehistoric origins. Today, the float process is used to create high-quality, flat glass for construction and automotive industries. Modern glass is typically made up of silica sand, limestone (which adds strength and durability), soda ash (which increases the melting temperature of the glass), dolomite (which further contributes to glass’ resistance to melting) and glass cullet (which accelerates glass melting as it goes through the float process).

To learn more about how glass is made, check out this youtube video:

If you’re ready to take advantage of Pilkington’s float process and give your home or office a modern look, call us  today: (613) 932-6703.