The Indianapolis times. [volume] (Indianapolis [Ind.]) 1922-1965, 1925-11-03

close at hand. The industry is widely
scattered because bricks can he made
Of almost any kind Of clay, mixed
with sand. Brick clay consists large
~ of hydrated silicates Of aluminium.
with oxide oil carbonate Of iron, and
various other substances. When
they are burned, bricks of this com
position have a buff. salmon or red
color, due to the presence Of iron. If
much carbonate of lime or chalk is
present, the color is sulphur-yellow.
If sand is not already present In the
clay, it must be added. If there is
too much sand the bricks are likely
to crumble, and If there is too little
the bricks will easily crack.
In making bricks, the clay is
thoroughly cleaned and mixed with
water in what is known as a pug
mill" In this are rotating blades
which cut and thoroughly mix the
clay. Sometimes anthracite coal
dust is added to help in the burn
ing of the bricks. The mixture then
goes to the b~rick-making machine,
except in small plants, where it is
nodded by hand. There are three
general types of machines-the soft
mud machine, the stiff-mud ma
chine. and the dry-clay machine. In
the stiff-mud process. which is the
most generally used, the machine
has a. trough. with a feed hole at
the end and a delivery hole at the
otbar A capfro1 ~ carriao baavy
knives. so arranged that when the
shaft is turned the clay is thorough
ly mixed and kneaded, and forced
through the rectangular opening in
a column Of soft brick. This column
is cut in proper length by wires.
This process produces slightly
harder and more durable brick than
the soft-mud process, in which the
machinery presses the mixed clay
into molds. In the expensive dry
process the clay is almost dried be-
fore it is introduced into the ma
chine, and the bricks are made in
steel molds under great pressure.
Most Of the finest brick for artistic
front wall or decorative interior
work is made by this process.
Brick Is Dried
From the machines the brick goes
TO the drying tunnels to be dried for
about twenty-four hours in a moder.
ate temperature before being dried in
the kilns. Sometimes they are piled
in the open to dry slowly. but ar
officially dried bricks burn more
evenly. The drying tunnels are
heated usually by the exhaust heal
from the kilns. and the atmosphere
must be kept dry by ventilation de-
vices. If the air gets too moist, the
surface of the brick remains damp
for some time and the moisture from
the interior comes to the surface as
water, carrying with It the soluble
salts of the clay. These salts are de-
posted as the water e%vaporates,
leaving the white scum often seen
on improperly dried bricks.
The bricks are now ready for the
most important part Of the process
the burning. On this depends very
largely their strength and durability,
as the action Of the heat brings
about chemical actions which entire
ly alter the structure of the clay.
The bricks r piled in kilns so
arranged that the fire may reach
every part Of them. Sometimes the
bricks themselves are piled to make
their W kiln and a fire started in
side; by this method a great num-
Der Of bricks may be burned at n
time. The firing takes from ten to
fifteen days according to the method
employed. Bricks for ordinary pur-
poses are kept at a cherry.red heat,
with a continuous sheet of roaring
flame filing the whole interior Of
the kiln. Others for finer purposes
-