What is Glass

Technically, glass is any inorganic substance that has been heated passed its melting point and then cooled into a rigid object without crystallization.  Really any amorphous solid is considered to be a glass.  Amorphous solids cover a wide range of materials including organics like plastics, biological compounds, and resins.  I’ll be talking mostly (exclusively) about inorganic glasses.  For example, volcanic glass is an inorganic glass.  The first volcanic glass that comes to mind is obsidian, but pumice is also a volcanic glass because it lacks a crystal structure.  However, inorganic glass also covers a lot of territory, so I plan to focus on glass made from silicon dioxide.