Page 46 - Curriculum Visions Dynamic Book

Bottles
Bottles have been used as containers since about the third century a.d. However, for them to come into widespread use, production had to be made faster, and there had to be significant demand for them. The demand was brought about with the invention of the carbonation process
for making “soda pop” in the 1770s. The fizzy drink needed to be put into convenient containers that would stand up to the stress of the pressurized water and also be clean and preferably reusable. This was the event that stimulated the bottling industry.
The scale of the change to mass production was staggering. At the Great Exhibition of London in 1851 alone a million bottles of pop were sold. Beer followed in Denmark in 1870 when a special pasteurisation process had been developed that prevented the beer from spoiling. Bottled milk was also pasteurized, although the process was not widely used for this purpose until the 20th century.
Bottles with narrow necks cannot be made in a single stage. Instead, they are made in two stages. In the first stage the bottle is partly blown into shape by compressed air. The bottle is then transferred to a second mould where it is blown to the final shape. Each stage takes about 10 seconds.
Once moulded, the bottles are sprayed with tin chloride solution. It produces a thin film of tin oxide, which hardens the surface and helps the glass resist blows and rubbing when transported. Then a thin plastic is spayed on to make the glass work more easily in bottling machines.
One problem in using bottles was how to hold a cap on firmly. Many bottles had caps that were wired on (as sparkling wine corks still are today). But two developments changed this for most bottles. In 1858 John Mason developed
a machine for moulding a screw thread onto a bottle, and narrow neck bottles were developed by 1885. After this it was possible to screw a metal cap directly onto the bottle.
(Right) How automated bottling plants work. The gob of glass drops into a mould and is forced to the bottom with compressed air. Compressed
air is then blown up from
the bottom of the mould, partly forming the shape. The partly formed bottle is then transferred to a different mould where the blowing process is completed. The final mould spins so there is no seam on the outside of the bottle.
(Left) Bottles are the next most important glass product after window glass.
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