What is Glass?

An Overview of Glass, How Its Made, and the Benefits of Recycling

Whether you enjoy the nostalgia of drinking soda from a glass bottle or appreciate the beauty of recycled glass tiles for home design, you’re likely familiar with the aesthetic value of this amazing material. What do you really know what glass is and how it’s made? If not, you’ll know more once you read these quick facts about glass.

Discovering what glass is made of

The process of making new glass from raw materials is relatively simple and requires only a few ingredients. Here are the basics on what glass is made of:

  • Ingredients gathered: In general, glass is made from silica (SiO2, also known as sand or sandstone), sodium carbonate (Na2CO3), calcium oxide (CaO) from limestone, magnesium oxide (MgO), and aluminum oxide (Al2O3). Sometimes things like lead, boron, barium, thorium oxide, lanthanum oxide, and iron are added for various reasons (thermal and electrical properties, color, reflective qualities, etc.).
  • Creating molten glass: The glass mixture is heated to very high temperatures of approximately 2,500° Fahrenheit or higher for up to 24 hours to create molten glass. This requires enormous amounts of energy.
  • Cooling: The mixture is then cooled by several hundred degrees to a temperature that allows it to be worked to form the desired shape through blowing, pressing, drawing, or rolling.
  • Annealing: Once complete, a finished glass piece is put into a lehr where it is strengthened by cooling it down in controlled intervals.

Glass consumption facts

Glass is a high quality materials used to make everything from electronics, furniture, appliances, and food containers. We love to use glass because it is durable, inert, and because it is perceived as much more valuable than plastics and metals. The consumption of glass speaks for itself:

  • In the UK, the average family goes through 330 glass bottles and jars or more annually and only 30% of those containers are recycled.[1] In all, glass makes up about 7% of the average UK household’s rubbish bin every year, which resulted in 2.5 million tones of glass sent to landfills in 2001.[2]
  • The glass trash created in the US in 2008 was approximately 12.2 tons and only 23% of that was recycled.[3]
  • By comparison, Canadians recycle only 17% of their used glass.[4]

Benefits to recycling glass

As far as recycling stats go, those for recycling glass are pretty rosy. That’s because the benefits of recycling glass are substantial:

  • Energy and water savings: Since glass cullet can be melted at much lower temperatures than making glass from scratch, recycled glass production results in 20% less air pollution and 50% less water pollution.[5] Recycling just one glass bottle saves enough energy to run a 100-watt light bulb for one hour, power a computer for 25 minutes, or run a washing machine for 10 minutes.[6]
  • Saved landfill space: True, glass is inert and therefore does not pose any pollution hazards to the environment, however it does take up physical space. Landfills require are costly to run and chew up natural habitats. Instead of sending useful glass products to the landfill, by recycling glass, much landfill space is saved.
  • No loss of quality: Glass can be infinitely recycled without any deterioration in the structure of the material. “New” glass products can consist of up to 90% recycled material.[7][8]
  • Raw material savings: Though the raw materials used to make glass are abundant in the earth, mining them does result in environmental degradation. Using recycled glass to create 1 tonne of new glass results in a reduction of raw material requirements of 1.2 tonnes.[7]
  • Cost savings: Making glass from cullet is much less expensive than making it from raw materials. This process requires lower temperatures which has the added benefit of prolonging the life of furnaces used in glass making.[8]

 






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References

1 Amazing Facts. (n.d.). Retrieved July 5, 2010, from The British Glass Website: http://www.britglass.org.uk/LocalAuthorities/AmazingFacts.html

2 Glass recycling information sheet. (n.d.). Retrieved July 5, 2010, from Waste Online: http://www.wasteonline.org.uk/resources/InformationSheets/Glass.htm

3 Wastes - Resource Conservation - Common Wastes & Materials - Glass. (n.d.). Retrieved July 5, 2010, from US Environmental Protection Agency: http://www.epa.gov/epawaste/conserve/materials/glass.htm

4 Canada vs. The OECD: An Environmental Comparison. (n.d.). Retrieved July 5, 2010, from Environmental Indicators: http://www.environmentalindicators.com/htdocs/PDF/CanadavsOECD.pdf

5 Recycling Glass - How it helps environment. (n.d.). Retrieved July 5, 2010, from World Wildlife Fund: http://wwf.panda.org/about_our_earth/teacher_resources/project_ideas/recycling_glass/

6 Amazing Facts. (n.d.). Retrieved July 5, 2010, from The British Glass Website: http://www.britglass.org.uk/LocalAuthorities/AmazingFacts.html

7 Glass recycling information sheet. (n.d.). Retrieved July 5, 2010, from Waste Online: http://www.wasteonline.org.uk/resources/InformationSheets/Glass.htm

8 Wastes - Resource Conservation - Common Wastes & Materials - Glass. (n.d.). Retrieved July 5, 2010, from US Environmental Protection Agency: http://www.epa.gov/epawaste/conserve/materials/glass.htm

 

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