-3500 – glass

Naturally occurring volcanic glass (obsidian) was use before we learned to make glass around -3,500 in Egypt and Mesopotamia. The earliest form of glass made by humans was probably glazes that were used on ceramic pots. By mixing crushed quartz with calcite (calcium carbonate) from limestone, a solution is produced which can be fired into a glaze known as faience. Egyptian faience was often tinted with pigments from copper compounds, creating glazes in a range of blue-green hues.

Glass is made from melting sand (silicon dioxide) into liquid form, then allowing it to solidify into a transparent pane or body. But sand melts at a high temperature, requiring either a high temperature furnace or the addition of soda ash (sodium carbonate) to lower the melting temperature of the sand. Glass making was probably accidentally discovered when stones made of soda ash were placed into a fire made on a bed of sand, like a beach. The heat from the fire melted the sand and soda ash together into glass.

PREREQUISITE:
ceramics
-7000 – copper age

CONCURRENT:
-3300 – bronze age

SUBSEQUENT:
1595 – microscope
1608 – telescope
1612 – thermometer
1643 – barometer
1855 – vacuum tube

SEE ALSO:
Glass Grows Up

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