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A very special material
Glass differs from other materials in its very
particular physical-chemical characteristics. Its viscosity
varies directly in function of its temperature : fluid when
fused (around 1400° for normal glass), it becomes progressively
thicker as it cools (around 800°C) and finally reaches
a stage where it gains a solid elasticity at ambient temperature.
The amount of time during which glass has a
thick consistency that makes moulding possible is called the
working stage : it varies in function of the composition of
the glass, which can be made more or less sensitive to variations
in temperature, and its malleability which can be regained
by a brief heating.
It reaches a remarkable level of plasticity
and can thus be moulded by hand, poured, pressed, drawn, laminated,
blown, glued. At 500°C it begins to solidify and becomes
breakable.
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