built, should be well selected: not too distant from the furnace
pot-arch, of uniform temperature, neither below fifty-five nor above
eighty—above eighty would dry the pots too fast, and below
fifty-five is not desirable, although a temperature as low as thirty-two
would not absolutely injure them. A middle or ground floor is preferable
to an upper floor, which in summer would be too much exposed to the
heat of the sun, and in winter too cold. The ceiling should be well
secured against particles of plaister dropping into the clay, and the
floors should be well ploughed and tongued, to prevent a substratum of
cold air, which in any case is difficult to avoid. At only four feet
from the floor, the upper and lower temperatures will often differ as
much as ten degrees, to the great danger of breakage in drying.
Three months may be adequate for drying
a pot, but four or six months are preferable; the large covered pots,
similar to those in the engraving, will contain about eighteen hundred
weight of melted glass: they measure three feet external diameter, and
three feet high, to the filling part, and weigh about ten hundred weight.
Pots for coloured glass.
This description of pot is used for white Flint Glass; for coloured Glass,
three small pots, two side by side and one above, are used in melting;
and the three fill up the same space in the furnace as that occupied by
one large pot of the above dimensions.
Upon the durability of the melting pots,
(all other arrangements and management being good,) the profit and
success of the manufacturer chiefly depend. Large melting-pots, with
the cost of coals and attendance to heat them for the furnace,