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

APPLIANCES FOB SMELTING THE ENAMEL MASS. 109
tents of the latter can be examined, the plug at the bottom
knocked out, and a fresh charge inserted.
The arrangement of this class of furnace exhibits great
similarity with that of an ordinary glass furnace, and is more
economical in consumption of fuel than when each crucible
has to be heated separately.
For larger establishments, the author has designed a
furnace to hold nine or twelve crucibles, as shown in section
in Fig. 11, and in plan in Fig. 12. The crucibles are mounted
on conical supports, resting on an arch under which the
FIG. 11.
vessels for catching the molten mass are situated. The heat
for melting the charge in the crucibles ascends from two
hearths, F, and the object of the partition walls, S, is to unite
the two currents of hot gases and convey them to the chimney,
E. The top of the furnace is formed of a thick fireclay plate
pierced with nine (or twelve) openings into which the crucibles
fit, the latter being very tall in proportion to their breadth,
in order to hold a larger quantity of the enamel mass, which
shrinks considerably in bulk as it fuses.
For works of extra size, the best smelting furnaces are
those wherein the crucibles, instead of being exposed directly