Up: Glassmaking
Reminiscences
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Chemists estimate that one hundred pounds of
pearlash contain thirty per cent. carbonic acid. In refining, it loses
on the average fifteen per cent. in weight.
Phosphate of soda brightens glass.
Borax brightens, but hardens glass.
Twenty-five silver dollars refined will give
thirty-five ounces of nitrate of silver.
A square foot of furnace clay weighs one hundred
and twenty pounds.
Alum, calcined, loses in weight sixty per cent.
Crude flint batch, melted and ladled out, loses
in the average fifteen per cent. in weight.
Hard coal will measure forty cubic feet to a
gross ton.
Glass in water. There are some peculiar
phenomena connected with hot glass and water. If a ball of red-hot iron is
placed in a vessel containing cold water, the latter is quickly agitated.
But a ball of melted glass of equal weight dropped in cold water will
produce no immediate agitation. The water will remain for some time
quiescent; but when the glass is cooled to about half its highest
temperature, it agitates the cold water violently.
Technical terms, descriptive of glass, such as
crystal, flint, tale, may be derived from these facts: the French used
for their base crystal stones, burnt and ground fine; in England they
had recourse only to flint stone, treated the same as the French used
their blocks of crystal; tale was derived from the mode of selling, the
best glass being sold only by weight, while light articles were sold
tale.
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