How is Glass Made?

The Pilkington Process

Glass is made from melting sand into a liquid. You won’t see that happening at your local beach though. Sand melts into a liquid state at around 1700˚ C (or 30390˚ F)! In a commercial glass plant, sand is mixed with cullet (recycled glass pieces), soda ash and limestone and is then heated. The soda helps reduce the sand’s melting point which helps reduce the overall energy—and cost—needed to melt it. The by-product of adding the soda is that it produces glass that dissolves in water, so limestone is added to stop that from happening. The end product is called soda-lime-silica glass and it’s the most often used glass.

The strange part is that no matter how hard you try to cool sand after it is has been heated to 1700˚ C, it never turns back into a sold again. It becomes what scientists call an amorphous solid, which is like a hybrid solid and liquid.

Depending on what type of glass is being created, the melted sand can be poured into molds to make bottles or poured over the surface of molten tin to make flat sheets of glass used in windows and doors.  The float glass process is called the Pilkington Process, named after the British glass manufacturer Pilkington, who pioneered the technique in the 1950s.

Other chemicals can also be added to the original recipe that alters the properties or appearance.

Lead – makes leaded or crystal glasses. The lead has better reflective properties and therefore the glass seems to ‘sparkle’. This kind of glass also lends itself to be cut to form decorative patterns on the glass.

Boron –changes the thermal and electrical properties of the glass and is used to make Pyrex glassware which can withstand extremes of heat and cold.

Lanthanum Oxide –excellent light reflective properties and is used to make high quality lenses in glasses.

Iron – used to absorb infrared energy

Color Additives A range of additives can be used to make glass into different colors.

The cooling process can also be altered to create different forms of glass. Annealed glass, tempered glass and laminated glass are all types of glass that are created using the same basic sand recipe, but additional steps are taken during the manufacturing process to coat, heat treat or engrave the glass.

Learn more about how Wakefield Equipment supports glass manufacturers with a full line of glass handling equipment!