582 PLATED MANUFACTURE 



alloy consisting of copper and brass, which possesses the requisite stiffness for the 

 various articles. 



The furnace used for melting that alloy, in black-lead crucibles, is a common air- 

 furnace, like that for making brass. See BHASS. 



The ingot-moulds are made of cast iron, in two pieces, fastened together; the 

 cavity being of a rectangular shape, 3 inches broad, 1J thick, and 18 or 20 long. 

 There is an elevated mouth-piece or gate, to give pressure to the liquid metal, and 

 secure solidity to the ingot. The mould is heated till the grease with which its cavity 

 N is besmeared merely begins to smoke, but does not burn. The proper heat of the 

 melted metal for casting, is when it assumes a bluish colour, and is quite liquid. 

 Whenever the metal has solidified in the mould, the wedges that tighten its rings are 

 driven out, lest the shrinkage of the ingot should cause the mould to crack. 



The ingot is now dressed carefully with the file on one or two faces, according as 

 it is to be single- or double-plated. The thickness of the silver plate is such as to 

 constitute one fortieth of the thickness of the ingot ; or when this is an inch and a 

 quarter thick, the silver plate applied in one thirty-second of an inch; being by 

 weight a pound troy of the former, to from 8 to 10 pennyweights of the latter. The 

 silver, which is slightly less in size than the copper, is tied to it truly with iron wire, 

 and a little of a saturated solution of borax is then insinuated at the edges. This salt 

 melts at a low heat, and excludes the atmosphere, which might oxidise the copper, 

 and obstruct the union of the metals. The ingot thus prepared is brought to the 

 plating furnace. 



The furnace has an iron door with a small hole to look through ; it is fed with coke 

 laid upon a grate at a level with the bottom of the door. The ingot is placed imme- 

 diately upon the coke, the door is shut, and the plater watches at the peep-hole the 

 instant when the proper soldering-temperature is attained. During the union of the 

 silver and copper, the surface of the former is seen to be drawn into intimate contact 

 with the latter, and this species of riveting is the signal for removing the compound 

 bar instantly from the furnace. Were it to remain a very little longer, the silver 

 would become alloyed with the copper, and the plating be thus completely spoiled. 

 The adhesion is, in fact, accomplished here by the formation of a film of true silver- 

 solder at the surfaces of contact. 



The ingot is next cleaned, and rolled to the proper thinness between cylinders, as 

 described under MINT ; being in its progress of lamination frequently annealed on a 

 small reverberatory hearth. After the last annealing, the sheets are immersed in hot 

 dilute sulphuric acid, and scoured with fine Calais sand ; they are then ready to be 

 fashioned into various articles. 



In plating copper-wire, the silver is first formed into a tubular shape, with one 

 edge projecting slightly over the other; through which a red-hot copper cylinder 

 being somewhat loosely run, the silver edges are closely pressed together with a steel 

 burnisher, whereby they get firmly united. The tube thus completed is cleaned in- 

 side, and put on the proper copper rod, which it exactly fits. The copper is left a 

 little longer than its coating tube, and is grooved at the extremities of the latter, so 

 that the silver edges, being worked into the copper groove, may exclude the air from 

 the surface of the rod. The compound cylinder is now heated red-hot, and rubbed 

 briskly over with the steel burnisher in a longitudinal direction, whereby the two 

 metals get firmly united, and form a solid rod, ready to be drawn into wire of any re- 

 quisite fineness and form ; as flat, half-round, fluted, or with mouldings, according to 

 the figure of the hole in the draw-plate. Such wire is much used for making bread- 

 baskets, toast-racks, snuffers, and articles combining elegance with lightness and eco- 

 nomy. The wire must be annealed from time to time during the drawing, and finally 

 cleaned, like the plates, with dilute acid. 



Formerly the different-shaped vessels of plated metal were all fashioned by the 

 hammer ; but every one of simple form is now made in dies struck with a drop-ham- 

 mer or stamp. Some manufacturers employ 8 or 10 drop machines. 



Figs. 1623 and 1624 are two views of the stamp : A is a large stone, the more massy 

 the better ; b, the anvil on which the die, c, is secured by four screws, as shown iu the 

 ground plan, fig. 1025. In fig. 1623, a a are two upright square prisms, set diagonally 

 with the angles opposed to each other ; between which the hammer or drop, d, slides 

 truly, by means of nicely-fitted angular grooves or recesses in its sides. The hammer 

 is raised by pulling the rope,/, which passes over the pulley, e, and is let fall from 

 different heights, according to the impulse required. Vessels which are less in dia- 

 meter at the top and bottom than in the middle, must either be raised by the stamp in 

 two pieces, or raised by a hand-hammer. The die is usually made of cast steel. 

 When it' is placed upon the anvil, and the plated metal is cut into pieces of proper 

 size, the top of the die is then surrounded with a lute, made of oil and clay, for an 

 inch or two above its surface ; and the cavity is filled with melted lead. The under 



