Glass is an inorganic product of fusion that has cooled to a rigid state without crystallizing. According to the Center for Glass Research at the New York State College of Ceramics at Alfred University:
- Glass is typically hard and brittle and has a conchoidal fracture.
- A glass may be colorless or colored. It is usually transparent, but may be made translucent or opaque.
- When a specific kind of glass is indicated, such descriptive terms as flint glass, barium glass, and window glass should be used following the basic definition, but the qualifying term is to be used as understood by trade custom.
- Objects made of glass are loosely and popularly referred to as glass; such as glass for a tumbler, a barometer, a window, a magnifier, or a mirror.
Is Glass Solid or Liquid?
There are four basic states of matter: solid, liquid, gas, and plasma. In a solid, molecules are ordered in a structured way, called a lattice. In a liquid, molecules are disordered and they are not rigidly bound. In a glass, however, we have the unique characteristic of a solid whose molecules are not ordered yet they are still rigidly bound. This situation has caused some chemists to refer to glass as a "supercooled liquid" rather than a solid. This would be a different state of matter than, say, freezing water; as water passes below the freezing point and becomes ice it forms a crystal and exhibits the properties of a standard crystalline solid.
Glass is produced industrially by melting a mixture of calcium carbonate (limestone), sodium carbonate (soda), and silicon dioxide, which is a major component of sand. Quartz sand, which is rich in silicon dioxide, is the most commonly used type of sand. The subsequent product, once cooled, is glass.