1902 Encyclopedia > Brass

Brass




BRASS, an alloy of copper and zinc, the composition of which will be discussed under the heading COPPER. In this place we have to do simply with its history, and the various applications of the alloy in the arts. Although the term brass frequently occurs in Scripture from the era of Job downwards, there is no indication that brass, as known in modern times, was in use previous to the period of the Roman empire. By the Romans a compound was used under the name oricalchum or auricalchum, which appears to have possessed the composition and properties of brass. With their conquests they carried a knowledge of the arts they cultivated into the countries they subdued, and from these the art of preparing the alloy extended with civiliza-tion throughout Europe. The earliest traces of brass in Great Britain are found in the mediaeval monumental "brasses," found commonly over the tombs of civil and ecclesiastical dignitaries (see BRASSES). That the alloy was manufactured in England during the reign of Henry VIII., however, is indicated from the passing of an Act of Parlia-ment prohibiting, under severe penalties, the export of brass, a prohibition which was not withdrawn till so recent a date as 1799, During the reign of Queen Elizabeth the manufacture was systematically developed and extended, and a patent for working calamine stone (the principal ore of zinc) and making brass was granted by the queen to William Humfrey and Christopher Schutz, securing to them the exclusive right of manufacturing brass. The patent rights granted to these persons were gradually ex-tended and merged into a company under the name of the " Governors, Assistants, and Societies of the City of London of and for the Mineral and Battery Works," which con-tinued to exercise its functions down to the year 1710. In the year 1721 it was estimated that about 30,000 persons found employment in the brass industries. From a very early date brassfounding was prosecuted in Birmingham, and by degrees it there assumed more important proportions till it has become the most distinguishing industrial feature of the town. The late Mr W. Aitken, in his valuable report on brass and brass manufactures, to which source of practical information we have to express our obligation, says :—" What Manchester is in cotton, Bradford in wool, and Sheffield in steel, Birmingham is in brass; its articles of cabinet and general brass-foundry are to be found in every part of the world; its gas-fittings in every city and town into which gas has been introduced from Indus to the poles."—(Birmingham and the Midland Hardware Districts, London, 1865.)
The brass trade of the present day is, according to Mr Aitken, conducted under nine different heads —(1), brass-casting ; (2), cabinet, bell, and general brassfoundry; (3), cock-making and plumbers' brassfoundry; (4), stamped brassfoundry; (5), rolled brass, wire, and sheathing; (6), tube-making; (7), lamp-making; (8), gas-fittings; and (9), naval brassfoundry. It frequently happens that several of these departments are carried on in the same establishment; but numerous as are these divisions, they by no means exhaust the industries in which brass plays a principal part. Thus the pin manufacture, button-making, and the gilt jewellery trade, are eminently characteristic of Birmingham, and in these brass is the principal metallic substance employed. According to the different forms under which brass is to be employed it is fashioned by the various pro-cesses of—1st, casting; 2d, rolling and drawing; 3d, stamping; and 4th, tube-drawing and casing; and to these, with 5th, brass-finishing, we shall briefly allude.
Casting.—-The first operation necessary in connection with casting is the preparation of patterns of the object to be cast. Castings, of course, vary in all degrees in intricacy and elaboration of details, and the getting up of the more ornamental patterns necessitates the employment of persons of artistic ability to prepare the design, and superior artisans to finish the pattern blocks. Three classes of castings are recognized in the trade—1st, common castings, made from any plain pattern, an impression of which can be formed and the pattern taken out without breaking the mould; 2d, cored castings, such as plumbers' cocks and other tubular work, where the metal must be poured round a central core; and 3d, false-cored castings, where the pattern is so undercut that the mould must be built up of such a number of separable sections as the intricacies of the pattern may require. When the mould is formed each of these sections is lifted off, the pattern is taken out, and they are then built together in their original position. This descrip-tion of moulding requires much skill and dexterity. Moulds are made in sand of a free, fine-grained, and uniform character ; and moulding-boxes of wood or cast-iron which fit together in two or more parts, with moulding-boards of wood and clamps to hold the parts together, are employed in casting. In the forming of common castings, the lower division of the moulding-box is packed with sand, and the pattern, if deep, is driven half its depth into it, parting sand is dusted over the surface, and the upper part of the box is fitted on and similarly packed with sand. When the box is filled, a moulding-board, forming a top or bottom to it, is laid on, the two halves of the box are separated, the pattern with-drawn, and "gates" or channels formed between the mould and the aperture by which the metal is poured in. The surfaces are then dusted over with flour or powdered charcoal, and the mould placed in an oven to dry. On their with-drawal from the oven the two parts of the moulding-box are clamped together, the molten metal is poured in, and a perfect copy of the pattern produced. In making common castings as many patterns as the superficial area of the moulding-box will accommodate are cast at once, " gates" leading to the entire series; and for many plumbers' cast-ings, &c, a series of half patterns, with moulded gates, are fixed on two sides of a plate by which the whole may be moulded and finished at one operation. The cores for tubu-lar work are separately made, and are supported on bearings in the mould. When the casting is cold the hardened core is picked out, and the article is then ready for finishing. Eine ornamental castings which contain minute details are moulded with special care in very fine sand, faced with charcoal powder, which faithfully reproduces the most delicate lines. The metal is poured direct from the crucible in which it is prepared, by the aid of strong tongs, and all spilt metal is carefully swept up, cleaned, and remelted.
Sheet Rolling and Wire Drawing.—The raw material of a large proportion of the brass trade consists of sheet-brass, as from it stamped work of all kinds is prepared, and jointed tubing and sheathing are made; and, generally, the processes of rolling must be adopted when sheets of large dimensions or of great thinness are required. For the purpose of rolling the metal is melted and cast in broad flat moulds of cast-iron; and in cases where a large quantity is dealt with, the moulds are hewn out in granite. These moulds are rubbed with oil and powdered with charcoal before being used. The ingots for rolling, termed " strips," are in the cold state passed successively between rolls (pairs of chilled-iron cylinders) of large size which squeeze them out and extend them lengthwise. As often as necessary in the process the sheet is annealed in a muffle or reverberatory furnace, being allowed to cool down after each annealing. The sheet is finished, after " pickling " in acid, by passing it through a pair of highly polished rolls. Muntz's sheathing metal is a form of brass containing a large proportion of

zinc, and as this alloy can be rolled out hot it is much more [ cheaply and expeditiously prepared than ordinary sheet i brass.
Wire Drawing.—Brass wire is consumed in enormous quantities, first and chiefly for pin-making, next for shoe-rivets, then for brush-making, for paper-makers' wire web, and many other purposes. The metal for wire drawing is rolled into long strips of a suitable thickness and cut into " strands " by means of slitting rolls. The strands, which are square in section, are drawn through a succession of circular holes in a steel draw-plate, till the desired degree of fineness is reached, and are wound upon a rotating drum or block. The wire has to be repeatedly annealed as it passes through the plates of ever-diminishing gauge.
Stamping.—A large number of useful articles, as well as many ornamental details, which were formerly produced by the process of casting, are now cheaply and expeditiously made by stamping out of sheets of rolled brass. In this way the ornamentation applied to the cheaper kinds of gasaliers, balance-weights, chain-links, &c, are formed, and cornice-pole ornaments and curtain-rings made ; and the process is also applied to the making of door and shutter knobs, finger plates, and lamp-burners, and to the striking up of many useful articles, such as basins and other vessels. In the process of stamping, a die, in which the pattern to be formed is sunk, is prepared by the ordinary process of die sinking, and securely fixed to a heavy iron block sunk into the ground. From each side of this block rise two cast-iron guide pillars, which act as guides to the heavy hammer or ram arranged to slide up and down between them. Into this hammer a " force," or exact counterpart of the sunk die, is fitted, so that on the fall of the hammer the force exactly fits into the die. The work of the stamper in raising his hammer is much lightened by passing the lifting belt over a pulley attached to a shaft moved by steam-power. By this arrangement the workman has only to hold his cord sufficiently tight to create the friction between the belt and pulley necessary to raise the weight, and by letting go his hold, the stamp is allowed to fall with its full momentum against the die. In a compound of such hardness and brittleness as brass it is necessary to raise any pattern by repeated strokes, annealing the metal between each separate blow. The number of blows neces-sary to bring up any pattern depends on the depth and convexity of the die. The " forces," or counterparts of the die, are made of lead, tin, or other soft metal, while for finishing the stamping when the die contains fine details a " force " made of brass is employed. A modification of the steam-hammer has been adapted for use in the pro-cess of stamping. Stamped work as compared with castings is deficient in depth and richness, as it is not practicable to attain any great boldness and sharpness of outline, and the " force " having to fit into every portion of the die, no undercutting is possible. Globular articles, such as balance weights, are stamped in two (or if necessary more) parts and the pieces joined by soldering. Mr James Atkins of Birmingham has patented an ingenious method of filling stamped shells, such as balance-weights, with molten iron by simply keeping the shell in water while it is being filled.
Tube-making.-—Brass tubes are of three principal kinds : —1st, ordinary soldered; 2d, cased; and 3d, solid tubing. Plain soldered tubes are made from sheet-brass by cutting off, with circular shears, strips of the breadth necessary for the gauge of the tube to be made. These strips are passed through " cupping-rolls, " by which they are partially bent round. The end of the strip is then formed into a tang, caught and drawn through a tool called a conductor, which folds over the strip into a circular form, bringing the two edges into close contact. The tube so formed is tightly tied up with wire at short intervals to keep the edges together in the process of soldering ; a mixture of granu-lated brass and borax is filled into the seam, and the tube is passed slowly through a strong heat in the soldering stove, which melts the granulated brass and so unites the edges. The wires are then cut away, and the superfluous solder filed off, the tube is pickled in sulphuric acid, and again passed through the steel conductor. In the case of tubes which, require great accuracy of internal gauge, a man-dril or solid cylinder of steel is placed inside the tube before it is finally passed through the tool. The external pressure causes the tube to fit closely to its internal support, and while the outside takes the outline of the steel conductor, the inside is made true to the shape of the mandril. Tubes of any given section are thus formed by the use of mandrils having the outline required. Ornamental patterns are impressed on plain tubes by fitting them on mandrils and passing them through a tool, which consists of a strong iron frame carrying three or more rollers so mounted that the open space between their external edges has the sectional form of the tube to be ornamented. On the external face of these rollers is sunk the design which is to be impressed on the tube, and as it is drawn through them the powerful squeeze they give is sufficient to impress orna-ments of considerable depth and boldness. Cased-tubes or rods, that is, tubes or rods of iron cased in brass, were invented in 1803 by Sir Edward Thomason, who thus described his invention :—" In watching the operation of drawing brass and copper tubes upon the mandril, I found it required as much power to slide off the hollow tube from the mandril as was required to draw it on. Reasoning from the adhesion of the brass tube to the steel mandril, I found by experiment that the union of copper and iron or brass and iron could be firmly attached by pressure, and conceived that such an application would be useful for making copper bolts for shipping, solid brass rods for stair carpets, solid brass to go round the top of a room to suspend pictures, as curtain rods for drawing-rooms, and as balustrades for staircases." Wood is cased in brass by a similar process, and used for such purposes as brass cornice-poles. Solid or seamless brass tubes, which are in very extensive demand for locomotive and other steam boilers, are made by drawing down short thick cast cylinders of brass till they reach the desired gauge and thinness. The instrument in which this drawing is accom-plished is similar to the apparatus for impressing orna-mental patterns on plain brass tubes. Four steel rollers are mounted in a strong frame, the sectional outline of the outer surfaces of which have the size and form to which the tube is to be drawn, and through a series of such tools the cast cylinders are passed, after annealing at each opera-tion. Mr G. F. Muntz in 1852 patented a method of drawing tubes cast in an oval form in the heated state.
Brass Finishing.—The operations in brass finishing com-prise " dipping, " " burnishing," and " lacquering," and in some cases brass-work is finished by " bronzing." After the article to be finished has been cleaned by pickling in acid, it is passed for dipping into an earthenware jai con-taining a solution of aquafortis (nitric acid). For bright dipping the acid is used strong, and the brass is imme-diately withdrawn from the bath, but for "dead" dipping, i.e., for producing a bitten, frosted appearance, the bath is made weaker and the metal left in it till a creamy appear-ance is seen on the surface. Burnishing is accomplished by rubbing with polished steel tools, called burnishers, the parts of dead dipped work which are to be brightened. The work is then passed through water soured with acid, rinsed, and dried in boxwood sawdust. For lacquering, the work is heated over stoves, and while it is hot, a coating of varnish, made of seed-lac dissolved in spirit, is carefully

and uniformly spread over the surface. Bronzing consists in applying to the surface of the metal an opaque pigment, which alters its colour. Ordinary brassfounders' bronze consists of a solution of hydrochloric acid and sal-ammoniac, or of the same acid, arsenic, and smithy scales. It is chiefly to cabinet brassfoundry and stamped work that such finishing processes are applied.
Vessels of brass for cooking and other domestic purposes
are very extensively employed in the East Indies, and the
alloy is there also a favourite material for the bangles
and other personal ornaments of the lower orders. A large
trade is carried on in brass wire, for ornamental purposes,
between Birmingham and various African stations ; a
species of currency called Guinea rods, made from thick
brass wire, is made and exported to the Guinea coast;
and a kind of cast-brass coin, called a manilla, current in
the equatorial regions of Old Calabar, is frequently supplied
by Birmingham manufacturers. (J. PA.)









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