Glass may be defined, physic ally, as a rigid under cooled liquid having no definite melting point and a sufficiently high viscosity (>than 10 Pa-s) to prevent crystallization; and chemically, as the union of non-volatile inorganic oxides resulting from the decomposition and fusion of alkali and alkaline earth compounds, sands and other glass constituents, ending in a product with random atomic structure.
Glass has many uses because of its transparency, high resistance to chemical attack, effectiveness as an electrical insulator and ability to contain a vacuum.
In order to produce these various glasses, large tonnages of glass sand are used. Soda ash, salt cake, and limestone or lime are required to flux silica. Inaddition, there is heavy consumption of lead oxide, pearl ash (Potassium Carbonate), salt peter, borax, boric acid, arsenic trioxide, feldspar, and fluorspar, together with a great variety of metallic oxides, carbonates, and the other salts are required for colored glass.