Last Updated: Dec 06, 2022     Views: 57

Raw glass and pieces of broken glass from a cooled melt, like this colorless chunk of glass, are called cullet.

Glass is commonplace in the modern world, and humans have been making and using glass for thousands of years. Amazingly, we continue to make discoveries about this material and to find new ways of using glass in our homes, laboratories, art, and technology.

Natural Glass

Most glass is manufactured, but it can also be created naturally. In rare instances, cataclysmic events like volcanic eruptions, meteor impacts, or lightning strikes can make this natural glass, but only when the affected magma or rocks also contain specific combinations of chemical elements. In other words, it takes more than just a rock and a burst of heat to create glass naturally.

Manufactured Glass

The most common kind of glass that humans make is soda-lime glass. Soda-lime comes from two compounds used to create this glass: soda or sodium carbonate and lime or calcium oxide made from limestone.  

When silicon dioxide, often called sand, is mixed with the soda and lime, heated to over 2000°F/900°C, and given time to react chemically, a hot lava-like liquid is created. In its molten state, glass can be shaped by hand or machine, then cooled to a solid form.  

It takes a significant amount of knowledge and skill to manufacture glass. The correct proportions of chemical compounds must be adequately mixed, brought to the optimal temperature, and then cooled at the appropriate rate to ensure it does not crack or break. 

The Structure of Glass 

The remarkable thing about glass is that it follows the rules of chemistry that determine which atoms attach to other atoms. But, unlike minerals and crystals, the atoms do not form an ordered pattern when molten glass becomes solid. 

Glass is a special kind of solid – a disordered, non-crystalline solid. 

And because glass stays disordered even when it solidifies, it is easier to put tiny amounts of other elements into the mix. Glassmakers add ingredients to change the color, to make it sparkly, or to make it opaque. Glass can also be strengthened to resist breaking when cooled or heated quickly or to resist shattering when dropped. New glasses are being developed all the time thanks to the versatility of this unique material.  

Learn More 

Watch/Read Now

  • Britannica, T. Editors of Encyclopaedia. "Glass." Encyclopedia Britannica, September 8, 2022.
  • Bullseye Glass Co., "What is Glass?," Youtube video, 10:47,

Read Later

  • Kassinger, Ruth. "The Science of Glass," Glass : from Cinderella’s Slippers to Fiber Optics. p. 28-36. Brookfield, Conn: Twenty-First Century Books, 2003.
  • Knapp, Brian J. "Introduction" Glass. p. 4-16. Henley-on-Thames: Atlantic Europe Pub. Co., 2003.
  • Pfaender, Heinz G., and Heinz G. Pfaender. "Glass, the material." Schott Guide to Glass /. 2nd ed. p. 16-35. London: Chapman & Hall, 1996.

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