What is Glass?

The explanation can get a bit complicated but I’ll try and keep it simple and not too technical. In science classes we are taught about the three states of matter being gas, liquid and crystalline. Although glass is a solid material it is a type of matter with a non-crystalline or amorphous structure. Glass is neither a liquid nor a solid but shares qualities of both.

Glass is created by heating dry materials to a viscous state and then cooling quickly. (Viscosity is a liquid’s measure of its resistance to flow.) The quick cooling process prevents a regular crystalline structure from forming like with a solid. Instead the atoms get locked in a disordered state like a liquid. So glass has the rigidity of a crystalline solid with the random atom structure of a liquid.


In nature glass is formed in one of three ways. When silicic lavas from a volcano are cooled quickly obsidian is formed. This is also known as volcanic glass. Fulgurite tubes are crusts of glass that are formed when sand is melted by a lighting strike. Fulgurite tubes are sometimes called “petrified lightning”. The third naturally occurring glass is moldavite. It does not contain a crystalline structure but rather a diagnostic pattern of striae and bubbles. Because of this it is believed that moldavite is formed from the outer surface of meteorites that have fused and melted during entry into our atmosphere.

The man made glass that we are familiar with is made by melting silica (sand) and other materials together. Some ingredients are added to stabilize and strengthen the glass like potash, lime, boric acid or caustic soda. Other additives like ground metal oxides are used to color the glass. Some colors of glass like pinks, reds and purples can be expensive because gold is used in the manufacturing process. There are many colors and types of glass available today.