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
In cases where there are no means of artificial drying, as at some
old-fashioned works, the thick clay is at once transferred from the
original settling pit to shallow depressions in the ground, called
“pans.” Ten or twelve of these, each holding from 40 to 50 tons,
should be provided for each settling pit; they measure from 20 to 40
feet square, and 2 feet deep, and are enclosed by granite walls, the
interstices of which are rendered impervious by plugging with moss. The
clay, filling two-thirds of their depth, is here left exposed to the
sun and wind, by which it is partially deprived of its moisture.
In order to complete its desiccation, the clay is removed from the pans
after three or four months’ exposure. A number of parallel incisions
are made lengthwise in the clay, by means of a knife attached to a long
handle; the strips are next divided transversely, by men with spades,
who throw the blocks on to a board, upon which they are borne by women
and children to the sandy drying yard, where, in fine summer weather,
they soon become dry. They are then collected, and piled away in sheds,
under a number of thatched gates or “reeders,” or are placed in some
sheltered position where air can circulate around them without their
becoming wet from rain.
When required, the blocks are scraped by women armed with hoes, before
being despatched from the works. The transport is often effected in
small casks, holding about half a ton. A few years since, a machine for
drying china-clay was invented by a mechanical engineer named Leopoldo
Henrion, of Sampierdacena, near Genoa. It is said that, by its use, the
operation can be effected in a few hours, at a relatively small cost.
Collins was first led to adopt his arrangement in consequence of the
formation of the ground; but he is inclined to recommend it in most
cases if practicable. Very large quantities of stone are required in
the dry pits, tanks, &c. Very often this is got, in part or entirely,
in the process of excavating the pits, &c.; but if it cannot be so
obtained, a very serious expense will be incurred, in some instances
amounting to several thousand pounds. The total cost of the works may
even be doubled from this cause, if stone has to be fetched from a
distance of several miles.
Public-domain text, read in full here on John Shaqi.
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