The raw material from which glass is made is silica, the most abundant of all the earth's minerals. Milky white in colour, it is found in beach in the world has been formed by water pounding rocks into tiny particles, sand is the major source of silica. Sand also contains other minerals, but silica is the main component because it is hard, insoluble and does not decompose, as it outlasts the others.
Pure silica has such a higher melting point that no ordinary fire would convert it into glass. It is said that the first glass-makers had lit their fire on sand which was impregnated with soda(compounds of sodium) left behind by evaporated water from a lake of sea. The soda reduces silica's melting point. Today, lime and soda are combined bottles, window panes and cheap drinking glasses. When glass cools, its structure does not return to the crystalline structure of silica, which is opaque. Instead, it forms a disordered structure rather than a frozen liquid, which is transparent. Other metas may be added to provide colour or to improve the quality of finished glass.
No comments:
Post a Comment