The walls of the
muffle should be about 1/2 in. thick, and the dimensions should
allow at least 1 in. of space all around for the passage of heat
between it and the walls of the kiln. By the time the clay of the
kiln is well dried, it will be found that it has all shrunk away
from the iron about 3/8 in. After removing all the paper, pack
this space-top, bottom and sides with moist ground asbestos. If
the cover of the pail has no rim, it may be fastened to the
asbestos and clay lining by punching a few holes, passing wire
nails through and clinching them. Fit all the parts together
snugly, take out the plugs in the top and bottom, and your kiln is
ready for business. The handle of the pail will be convenient for
moving it about, and it can be set on three bricks or some more
elaborate support, as dictated by fancy and expense.
The temperature required for baking earthenware is 1250
degrees--1310 degrees, C.,; hotel china, 1330 degrees; hard
porcelain, 1390 degrees-1410 degrees. These temperatures can not
be obtained in the above kiln by means of the ordinary Bunsen
burner. If will be necessary either to buy the largest size
Bunsen, or make one yourself, if you have the materials.
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