THE GLASS FORMING PROCESSES
Like treacle, glass is fluid at high temperature and its fluidity decreases as the temperature is reduced. Unlike water, glass has no specific melting or freezing point but is gradually changed from a solid to a liquid as the temperature is increased. It is this property of 'variable viscosity', which is used in forming a mass of glass into articles of beauty or utility.
Glass Blowing
Making Glass Containers by Automatic Process
Flat Glass
Glass Fibre Manufacture
Optical Fibre Manufacture
Glass Tubing
Automatic Domestic Glassware Production
Electric Light Bulb Production
Secondary Processing
Glass Blowing
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, although glass blowing is still carried out by 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 1000oC 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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Making Glass Containers by Automatic Process
Until the second half of the 19th century bottles were made by hand gathering, blowing and finishing the neck. A semi automatic method of bottle making was developed after 1850 but this has since been replaced by the fully automatic process. All bottles and jars are now made automatically by one of two methods - 'Press and Blow' or 'Blow and Blow'.
Click here if you would like to know more about the Press and Blow or the Blow and Blow Processes.
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Flat Glass
The main flat glass products are for high quality glazing in homes, offices, hotels, shops, vehicles public buildings and glass for horticulture; wired glasses for fire resistance; patterned glass for privacy and decoration; and a wide range of glass for environmental control and energy conservation.
Other uses for flat glass include toughened glass doors, suspended window assemblies, cladding for the exterior of buildings, mirrors and low-reflection glass for pictures and instrument dials. The two manufacturing processes for producing flat glass in the UK are the float glass and rolled glass processes.
Click here if you would like to know more about the float glass and rolled glass processes.
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Glass Fibre Manufacture
There are two main groups of glass fibre products: continuous glass fibre which is used for the reinforcement of plastics, rubber and cement; and glass wool, which is used for thermal insulation and which is produced by the Crown process.
Click here if you would like to know more about glass fibre manufacturing processes.
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Optical Fibre Manufacture
Communications are increasingly based on eletro-optic systems in which telephones, television and computers are linked by fibre optic cables which carry information by laser . Making glass optical fibres is a highly specialised aspect of glass manufacture.
Click here if you would like to know more about optical fibre manufacturing.
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Glass Tubing
Glass tubing is used in many products including scientific instruments, fluorescent lights and many other lighting applications. Glass tubes are made by the Danner Process or the Vello Process.
Click here if you would like to know more about the Danner or Vello processes.
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Automatic Domestic Glassware Production
Tumblers, wine glasses and pint pots are made using the Westlake machine which was originally developed for blowing bulbs for domestic lamps and radio valves. It has since been adapted for making drinking glasses at a rate of up to 55,000 a day.
Click here if you would like to know more about the Westlake process.
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Electric Light Bulb Production
The ribbon machine was developed for the high-speed manufacture of bulbs for domestic lamps, auto lamps and vacuum flasks.
Click here if you would like to know more about light bulb manufacture
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Secondary Processing
As part of the production process some types of glass are subjected to secondary processing such as annealing, toughening , coating and decorating.
Click here if you would like to know more about these processes.
