Glass is an amorphous solid. The term is usually applied to inorganic solids and not to plastics or other organics. Glasses do not have crystalline internal structure. They usually are hard and brittle solids.
Examples of glass include borosilicate glass, soda-lime glass, and isinglass. While there is no requirement for a glass to have a specific chemical composition, most common glass consists mainly of silicon dioxide (SiO2). Other elements or ingredients may be added to glass to alter its properties. For example, barium may be added to glass to increase its refractive index. Iron may be added to increase its absorption of infrared light. Cerium(IV) oxide is an addition that causes glass to absorb ultraviolet light.
While glass may have any of several chemical composition, most formulations display the following properties:
- Transmits visible light: Glass is generally transparent to the visible portion of the electromagnetic spectrum. However, the surface of glass will scatter or reflect light.
- Resists chemical attack
- May be poured, formed, molded, and extruded
- Potentially high tensile strength