The mould then is a square frame, mostly of iron, filled with peculiar dark red sand, which is pressed into a firm mass, in which the patterns of the casting are imbedded and their perfect shape impressed. The casters work at a large trough filled with the sand, and the workshop, with its forge, has some resemblance to a bakehouse where black bread is being kneaded into loaves. The first mould is made for what is called the “odd side” of the pattern—that is to say (in solid castings), the lower, or inferior side—and this serves as a sort of pattern to which the moulder refers in fine castings. The pattern being lifted off or out as soon as the sand-mould is sufficiently solid, the whole surface, in which the chasing of the pattern is clearly defined, is dusted with bean-floor or pounded “pot” first, and afterwards with loam, sand, charcoal, or coal-dust. This has the effect of making a smooth surface, and effectually filling the interstices in the sand, so as to prevent any raggedness in the casting. Each mould, or rather the two sides of the mould, are then placed near the surface and slightly baked, a channel having been made in the edge of each for conducting the melted metal to the pattern. The two sides are then placed together and held firmly by their pins and sockets, and the mould is ready for the casting. The “pots,” or crucibles of greyish clay, which turn red by the action of the fire, are in the furnaces like so many tall flower-pots. The dirty yellowish brass ingots, made on the premises at a large mixing furnace, having been first placed across the tops of the pots, that they may expand before being melted, are about twenty minutes afterwards reduced to a molten mass, above which hovers a light sea-green flame mingled with streaks of brilliant colour, like the water from a dyehouse; meanwhile the moulds have been placed in a slanting position, with the opening in the side upwards, against a bank of sand or brickwork, and everything is prepared for pouring. A man, who should be strong in the wrist, stands on the furnace, which has the openings at the top, like a French cooking-stove, and taking off the brick covers from the square aperture, whence rushes out a tongue of green flame, lifts out the pot with a pair of tongs, and after the dross is removed by the skimmer or grunter, hands it to the pourer, who fills each mould in succession. The fumes which rise from the midst of the coloured fire are peculiar and penetrating, and the zinc eliminated from the molten brass falls in a metallic snowstorm, its flaky particles adhering to everything with which they come in contact, while the resistance of the sand to the metal causes a series of reports like muffled pistol-shots.
Large Tongs. Small Tongs. Pot Holes. Skimmer. Grunter.
The brass cocks and plugs used in gas-fittings are all cast in one central stem, like cherries on a stick, their hollow forms being secured by means of cores made of hardened sand placed in the shape impressed in the mould. These are broken off the central stem with a pair of pincers immediately after casting.
The ornamental “vases” and larger ornaments which form the body of ordinary gas chandeliers and lamps are formed out of thin metal by a process called “stamping out,” the plates of metal being placed on a hollow die, upon which a heavy hammer, or rather weight, is brought down, being released from a latch and worked by the foot. The depth of the casting would make so heavy a blow necessary that there would be danger of splitting the metal, an accident which is prevented by the introduction of a leaden shape and a layer of clay, which is decreased after each blow of the hammer until the proper depth is gradually secured without injury.
The process called “reversing” is an operation which secures a hollow casting, the inner or hollow side being called the “reverse.” For this purpose a mould is made from one in wax, and the impression in the mould hardened, so that another model can be taken from it. This enables the moulder to secure a core which fits the impression in the mould, as one cup would stand inside another; and between the mould containing the sunk pattern and that with the projecting core there are placed strips of black clay, to secure sufficient thickness of metal, by not allowing the hollow to be too accurately filled. The pattern when cast is “laid out” on a hollow hemisphere of iron filled with pitch, and the irregularities of the casting removed by hand tools, files, rasps, and knives. In the case of figures, such as cupids, &c. forming ornaments for candelabra, the various limbs have often to be modelled in separate “cores,” which are afterwards baked hard, and put together like a puzzle-map, imbedded in the sand of the mould previous to casting. This requires great skill to effect successfully, and an experienced “reverser” is a man of mark in the factory.
Fork. Vent Wire. Sleeking Tool. Rasp. File. Vice. Pincers. Hammer. Double-headed Knife. Saw. Drawing Knife. Knife.
The completed castings are now removed to the chasing-room, where we may watch the gradual process of beautifying to which they are subjected, and the sharpening of the ornamental details by means of tool and graver, in a similar way to the first rough “laying-out,” which removes the irregularities of the pattern. The arms and branches which form a part of the gas chandelier work, as well as many of the scroll-work ornaments, are cast in halves, which are taken to the soldering-room, where a workman, seated at a forge-like furnace, heats them in the burning embers, and applies to the edges the solder, with which is mingled a flux of borax and water to secure its melting. The heat is increased by a blowpipe, which is in reality a double or jacketed tube, the inner one supplying gas, and the outer being connected with a large pair of bellows, and mixing atmospheric air with the lighted gas at the point of combustion.
The pickling room is a large shed-like place filled with tubs, troughs, and earthen pans. Into one of these, containing diluted aqua-fortis, the metal is plunged for the purpose of removing the scale produced on the surface by the action of the fire; from this it is dipped in a stronger solution, to undergo the process called “fizzing,” and its final baptism in pure acid restores the beautiful primrose colour which properly belongs to it. It is still dull, however, and goes to be “scratched,” an operation effected by means of a revolving wire-brush, turned by a wheel and treadle, and kept continually wet with water.