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Origins of Glass
Glass in many forms is associated with wine, bottles, glasses and decanters therefore it is worthwhile looking at its origins.
Since the Bronze Age (around 3,000BC) glass has been used for making a variety of objects. Originally made from a mix of sand, lime and an alkali (soda or potash) these remained the basic ingredients until the 17th century and the advent of lead glass. From these simplest of raw materials glass is a remarkable substance; coloured, clear, translucent or opaque are just a few of the ways that glass can be produced.
When heated the mixture becomes soft and workable enabling it to be formed into any number of shapes and sizes. The mass formed by melting cools to create glass but it lacks the crystalline structure normally associated with materials formed in this way (e.g.metals), retaining the random molecular structure of a liquid. This is why glass shatters when subjected to a sudden blow and why it deteriorates over time (devitrification).
Although with many variations there were four major manufacturing methods:
- Rod and core forming - first developed in the Bronze Age
- Free blowing - still used today but probably dating to to the 1st century BC
- Casting with moulds - Bronze Age to Roman times
- Blowing into moulds - led to development of square bottles
It is an interesting fact that in China before the 17th century glass was treated as a semi-precious stone; the cast glass was carved and polished like a gem. The European idea of blown glass was introduced to Emperor K'ang Hsi (1662-1722) by Jesuit missionaries he ordered a factory in the palace grounds of Peking to produce glass very much in the Venetian style.