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Glass Forming
Like treacle, glass is fluid at high temperature and
its fluidity decreases as the temperature is reduced...
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... but 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
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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'.
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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.
| Making
Glass Containers by Automatic Process |
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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has since been replaced by the fully automatic process.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'.
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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.
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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.
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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.
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| Optical
Fibre Manufacture |
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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.
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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.
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| Automatic
Domestic Glassware Production |
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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..
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| Electric
Light Bulb Production |
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The ribbon machine was developed
for the high-speed manufacture of bulbs for domestic
lamps, auto lamps and vacuum flasks.
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As part of the production process
some types of glass are subjected to secondary processing
such as annealing, toughening , coating and decorating.
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More information:
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