Glass is one of oldest raw materials known to mankind and has been used in production since time of ancient Egypt. It is a durable material with a variety of uses, ranging from windows and bottles to mirrors and scientific laboratory equipment. But how is glass actually made?
Glass is made by melting together a variety of raw materials, including sand, limestone, soda ash, and other substances. The raw materials are first heated to extremely high temperatures and then mixed together in a furnace, while furnace is carefully monitored to control temperature and composition of molten glass. This molten glass is then poured into molds, where it cools and solidifies into desired shape.
The heating of raw materials is key to production of glass. Sand, for example, must be heated to a temperature of around 1,700 degrees Celsius in order to become a liquid. Limestone and soda ash are heated to higher temperatures of around 1,500 and 1,400 degrees Celsius, respectively. The different materials are combined in furnace at appropriate temperatures to create a molten mixture known as a “frit.”
The composition of a glass mixture can vary from one application to another. For example, soda-lime glass, most common type of glass, is composed of sand, soda ash, and limestone. A glass that is used for insulation may contain different raw materials such as feldspar and borax.
Once desired composition of raw materials has been achieved, it must be worked and molded into shape of final product. This can be done by either hand-blowing or machine-blowing. With machine-blowing, molten glass is mechanically forced into desired shape by air pressure. With hand-blowing, a metal tube called a blowpipe is used to manually shape molten glass.
Once glass has been molded into its final shape, it is cooled and then inspected for any defects. If there are any, glass is then reheated, annealed, and cooled again until it is deemed to be of an acceptable quality.
Glass production is an art that has been perfected over thousands of years and is an important component of many modern items. By understanding entire process of glass production, you can appreciate intricacies of this ancient craft and science behind its development.