According to Martin (2001) ‘glass
can generally be divided into two groups: oxide glass and non-oxide glass. The
ingredients of oxide glasses include oxides (chemical compounds that
include oxygen). Non-oxide glasses are made from compounds that contain no
oxides, and which often instead contain sulfides or metals. Oxide glasses are
much more widely used commercially’. The common types of glass and their
chemical composition can be found at: http://www.texasglass.com/glass_facts/composition_of_Glass.htm.
The predominant ingredient used
to manufacture glass is sand. Sand occurs naturally on earth by the disintegration
of rock and mineral particles. The main component of each grain of sand is
typically silicon dioxide and the presence of silicon (Si) on Earth occurred by
falling meteorites known as aerolites. The chemical compound silicon dioxide,
commonly known as silica (SiO2)
is the oxide of silicon.
The British Glass Manufacturer’s
Confederation (2011) describes on their website how glass is manufactured:
Glass is made
by melting together several minerals at very high temperatures. Silica in the
form of sand is the main ingredient and this is combined with soda ash and
limestone and melted in a furnace at temperatures of 1700°C. Other materials
can be added to produce different colours or properties. Glass can also be
coated, heat-treated, engraved or decorated. Whilst still molten, glass can be
manipulated to form packaging, car windscreens, glazing or numerous other
products. Depending on the end use, the composition of the glass and the rate
at which it is allowed to cool will vary, as these two factors are crucial in
obtaining the properties the glassmaker is seeking to achieve.
Key dates in the history of glass production:
Earliest origins Historians
have discovered that a form of natural glass - obsidian - formed for instance,within the mouth of a volcano as a result of the intense heat of an eruption
melting sand - was first used by man as tips for spears.
4000 BC (Egypt) Evidence of
man-made glass in the form of glazes used for coating stone beads.
1500 BC The first hollow
glass container was made by covering a sand core with a layer of molten glass.
43 AD – 410 AD The
secret of glass making came to Britain with the Romans!
680 AD Evidence
of a glass industry around Jarrow and Wearmouth.
13th Century
AD Evidence
of there having been a glass industry in the Weald and the afforested area of
Surrey and Sussex around Chiddingford.
1845 AD The
modern glass industry really started to develop in Britain after the repeal of
the Excise Act in 1845 relieved the heavy taxation that had been enforced.
1851 AD Joseph
Paxton's Crystal Palace at the Great Exhibition of 1851 marked the beginning of
the discovery of glass as a building material. The revolutionary new building encouraged the use of glass in public, domestic and horticultural architecture.
1887 AD Glass
making developed from traditional mouth blowing to a semi-automatic process.
1907 AD First
fully automated machine was developed in America.
Recycling glass has a positive impact on the environment
as it takes less energy to melt recycled glass than it does to melt down raw
materials. Recycling also reduces the need for raw materials to be quarried therefore
saving precious resources.
References:
Emsley, J. (2003) Nature’s
building blocks an A-Z guide to the elements. Oxford: Oxford University
Press.
