Glass
By Rochelle Forrester
Ó All Rights Reserved
Publication Date 2006
The earliest known glass making was in ancient Egypt around 3,000 B.C. although Mesopotamia followed quickly thereafter. The basic requirements for making glass are silica (sand), an alkaline substance such as soda and lime (calcium carbonate). The earliest and simplest technique for glass manufacture was baked glazing. Baked glazing involved melting the silica, soda and lime and then coloring the product which was then poured into moulds to produce small statutes or jewelry. It was later discovered that a bottle or vase could be made by placing the molten glass around a core that could be removed when the glass cooled.
In the first century AD glass blowing was developed probably in the area of present day Syria. Glass blowing involved the molten glass being placed at the end of a metal pipe and a person blowing through the pipe which blew the glass up to the desired size and then the glass was shaped and decorated. The development of glass blowing opened up new technical and artistic possibilities for glass makers. The quality of the glass improved as its texture became more refined and it became more transparent and colorless. New molding techniques developed with the glass being blown into the moulds. Glass began to be used to make plates, pitchers and vases, objects which had previously been made mainly of metal or clay. The Roman author Pliny referred to the use of manganese oxide to rid glass of impurities so as to ensure that it was transparent.
Chemically glass is an amorphous noncrystalline solid. This means the atoms are arranged in a random rather than a regular pattern. This accounts for the optical qualities of glass such as transparency and causes the glass not to have a definite melting point. When heated the silicon in glass causes it to go into a state where it is a soft solid or viscous liquid. This state exists over a wide temperature range and explains why glass is able to be molded and blown into a wide variety of shapes.
If it had not been possible to invent glass, for example if no combination of materials could produce a solid transparent substance, then the effect on society would have been considerable. Eye glasses to correct defective vision would have been impossible and the microscope and the telescope may not have been invented. This would have meant our discovery of the world of micro-organisms may not have happened or may have been delayed until the 20th century and the development of other transparent products such as plastics. Progress in medical research and the discovery of disease would have been delayed or never happened. It would also have meant that our discovery of the universe from new planets to new galaxies would have been delayed until other transparent materials could have been developed. The earth centered astronomies of the pre–telescope age would have continued to be believed at least until some substitute for glass had been developed and could be used to create telescopes. This means the resources in nature had a significant effect on human history and if those resources had been different, then human history would have been different.