Pigments, Paint and Painting: A practical book for practical menTerry, George
Science
Pigments, Paint and Painting: A practical book for practical men
Terry, George
Paint; Painting, Industrial; Pigments
When the stream of clay-water enters the pits, it contains from 1½ to
3 per cent. of clay; and what is called a good washing stream will
carry about one ton of clay an hour. When the pit is full, the “hatch”
is drawn, and the clay is “landed” into the tank. The upper portion is
sufficiently fluid to run in of itself; but that near the bottom has to
be helped out by men using “shivers” of wood or iron, which resemble
large hoes; they are assisted by a small stream of water. The tanks are
commonly, but not always, rectangular, built of stone, and paved with
stone at bottom, often 60 feet by 30 feet by 6 feet or larger. Once in
the tank, the clay is left to settle, until it has the consistency of
cream cheese, the water being drawn off from time to time; it is then
ready to be trammed into the “dry.”
The “dry” is a large building erected in immediate proximity to the
tanks. It is always composed of two parts, the dry proper and the
“linhay.” The floor or “pan” of the dry is composed of fire-clay tiles
18 inches square, 5 or 6 inches thick at the fire end, and gradually
thinning off to 2 or 2½ inches at the stack end. The flues are built
of fire-brick, about 15 inches wide, 2 feet deep at the fire end, and
9 inches deep at the stack end. Each flue should be supplied with a
damper. The furnaces are built in and arched over with best fire-brick;
the fire bars run longitudinally, and are about 6 feet long. The grate
surface is about 2 feet 6 inches wide in front, and 4 feet 6 inches to
6 feet at back, according as each furnace supplies three or four flues.
The clay, brought in from the tanks in tram-waggons holding about half
a ton, is tipped on to the tiles, and spread in a layer from 9 inches
thick at the fire end to 6 inches thick at the stack end. The fire
end is loaded and cleared every day; the other end perhaps twice or
thrice a week, according to the length of the dry, thickness of tiles,
perfection of draught, &c. An average size for a first-class dry is
perhaps 15 feet wide and 120 feet long; but some have been constructed
considerably larger than this. The pan of the dry should be 6 or 8
feet above the linhay whenever possible, so as to afford storage space
for the dry clay, without expending labour in piling. The tiles should
be as porous as possible, for very much more water passes through
the tiles and into the flues than is driven upwards in the state of
steam. The temperature should never be allowed to rise so high that the
workmen cannot walk on the tiles, otherwise the clay may become baked
and damaged.
Public-domain text, read in full here on John Shaqi.
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