Manufactured since 12,000 BCE, glass is one of the most versatile substances on Earth. Glass is a supercooled liquid, rather than a solid, and used in many applications, in a huge variety of forms. In fact, almost everyone in the world uses glass in some way every single day.
Early examples of glass occurred naturally when rocks high in silicates (a common mineral) melted at high temperatures and cooled – this is mainly known as volcanic glass, though natural glass can also occur when lightning strikes silicate-rich sand on a beach.
Manufactured glass is generally made from silica, soda and lime. Other materials can be added for color or to frost the glass. Silica is found in a variety of natural sources, most often sand. Soda, or sodium carbonate, can be naturally or synthetically produced. Lime is ground from limestone, a type of sedimentary rock found in deposits all over the world.
The materials are heated to 1800 degrees Fahrenheit, poured into molds or blown into shape, and then cooled. When cooled, glassis a strong, minimally conducting substance that will not interact with materials stored inside. For this reason, glass is commonly used in scientific laboratories to minimize chemical reactions.
Glass is a favorable material to use with food and beverages as it resists chemical reactions, is easy to recycle, does not leach chemicals like plastics do and it can withstand high and low temperatures (although not at the same time.)
One common type of glass is borosilicate glass. By adding boron to silicate sand, soda and lime, manufacturers were able to produce a glass that resists breakage due to temperature variation. This type of glass is most often found in flashlights, lamps and telescopes.
Tempered glass is manufactured to be much stronger than other glasses. When broken, it breaks into small fragments rather than sharp shards – making it ideal for glass tables, refrigerator trays and various types of plates and cookware. Tempered glass is formed by introducing compression to the surface of glass as it is formed. Some manufacturers also laminate the surface to add more strength.
Commonly used in electrical applications, lead glass is a more expensive type of glass that withstands high temperatures. As the name implies, it contains a high level of lead oxide (at least 20%) and is not to be used for food or drink.
Not all glass is created equal! Commercial glass, used for anything from windows to dinnerware, can range in quality and safety as much as any other material (stainless steel, plastic, even wood) so it’s important to buy glass reusables from a trusted source.
Click here to see our growing line of reusables made from glass.