Up: Glassmaking
Reminiscences
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it distributes a regular and uniform heat to each pot, causing the
pots to last much longer, and fusing the metal better,-- important
items to mixers.
From three to five tons of fuel is the weekly
saving in a first-class furnace.
It is of vital importance to obtain pots that
will last a reasonable time. Clays of the finest quality are essential.
Each piece must be freed from any foreign matter, particularly sulphate
of iron, which often occurs. The burnt and raw clay should be well
mixed, wet, and frequently kneaded, or trod over by the naked feet.
Tenacity must be secured, sufficient that a roll twelve to eighteen
inches long can be suspended, and hold firmly together by its own
adhesiveness. The next point is to make the pots free from air blisters,
all portions being compact; then to dry them thoroughly, which requires
great care on account of the inequality of the different parts.
Pot-makers are not agreed as to the value of different clays, and
the use and proportion of raw to burnt shells. Some use sixteen parts
raw to eleven parts burnt, some fifty-five raw to forty-five burnt, some
equal proportions of each.
Manufacturers have mainly depended upon imported
clays, but the Western glass-makers have used Missouri clay with success.
In the east it has not yet come into general use. Of the imported, that
from Stowbridge is considered best. Garnkerk is a strong clay, and, if
well selected, will rival any other. The analyses are for
STOWBRIDGE,
| Silica, |
64
| parts,
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| Alumina, |
20
| "
|
| Lime, |
1
| "
|
| Iron, |
3
| "
|
GERMAN,
| Silica, |
46
| parts,
|
| Alumina, |
34
| "
|
| Iron, |
3
| "
|
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