Enamels and enamelling; an introduction to the preparation and ...

108 ENAMELS AND ENAMELLING.
furnace is supplied with fuel through the top ; and the
chamber below the ashpit contains a tub of water to receive
the molten mass of enamel.
The crucible is fitted with a lid, which projects beyond
the walls all round and is provided at the top with a knob
for lifting.
The bottom is perforated with an aperture which
is closed, each time the crucible is re-charged, by means of a
layer of quartz meal mixed to a paste with water.
FIG. 10.
A number of such furnaces (e.g., six) may be arranged
round a central flue to carry off the products of combustion,
and, by a slightly modified construction, the waste gases can
be diverted, first into the heating-up chamber and then under
the pan for calcining tin, or into the room for drying the
ware to be enamelled, etc. In such case it is advisable to
make the furnace of such a shape that the fuel is admitted,
not through the top, but by an aperture in the side, a little
higher than the upper edge of the crucible, so that the con-