Up: Glassmaking
Reminiscences
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PROPERTIES OF GLASS.
Glass has properties peculiarly its own; one of
which is that it is of no greater bulk when hot, or in the melted state,
than when cold. Some writers state that it is (contrary to the analogy
of all other metals) of greater bulk when cold than when hot.
It is transparent in itself; but the materials
of which it is composed are opaque. It is not malleable, but in
ductility ranks next to gold. Its
flexibility, also, is so great then when hot it can be drawn out, like
elastic thread, miles in length, in a moment, and to a minuteness equal
to that of the silk-worm. Brittle, also, to a proverb, it is so elastic
that it can be blown to a gauze-like thinness, so as easily to float
upon the air. Its elasticity is also
shown by the fact that a globe, hermetically sealed, if dropped upon
a polished anvil, will recoil two third the distance of its fall,
and remain entire until the second or third rebound. (The force with
which solid balls strike each other may be estimated at ten, and the
reaction, by reason of the elastic property, at nine.) Vessels, called
bursting-glasses, are made of sufficient
strength to be drawn about a floor; a bullet may be dropped
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