For nearly 2,000 years glass blowing by hand was the main method of forming glass articles. The last few years of the 19th century saw the beginnings of blowing glass by compressed air and the 20th century brought in the revolution of mechanisation. However, glass blowing is still carried out by skilled craftsmen today.
For glass blowing, a hollow blowing-iron or pipe is dipped into a pot containing molten glass and the glass is gathered at the end of the pipe by rotating it, similar to gathering treacle onto a spoon. The collected glass, known as the gather, cools to about 1000°C and is marvered (rolled on an iron slab) to form a parison. The parison is then manipulated by allowing it to elongate, re-heating it and blowing air into it to bring it into a shape that resembles the final article. It is then placed in an iron or wooden mould, which is kept wet by water, and the glass is blown to the final shape of the interior of the mould. There is no contact between the glass and the mould, due to the water which forms a cushion of steam. During the blowing the pipe is rotated continuously, preventing mould joints or other mould imperfections appearing in the glass.
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Many glass making terms have entered the language: 'Shut yer gob': a molten lump of glass is called a 'gob' to which the glass blower attached a tube to blow the glass into shape. The blower had to blow hard which made his cheeks very large. Today someone with a big mouth is told they have a big gob.