As we have said above, the modern uses of brass overlap those of bronze to a considerable extent; but it is not less true —and this fact deserves our special attention at present — that quite beyond the zone occupied by both alloys almost indistinguishably there lies a wide indus trial field that is still held by the copper-and zinc alloy almost to the exclusion of the cop per-and-tin alloy. In this connection it is well to note the adaptability of the former, as that is set forth in 'The Metallic W. T. Brannt, ed. (Philadelphia 1908), to the fol lowing effect: Generally speaking, brass should contain only copper and zinc, but many or most of the varieties found in commercial use as a matter of fact do contain small quan tities of iron, tin, arsenic and lead, and these admixtures are due either to contaminations mixed with the ores from which the copper and zinc have been extracted or to additions made intentionally in order to change the duc tility, color, fusibility, hardness, etc., of the re sultant alloy. Again, copper and zinc can be combined in many ways, the proportions vary ing within very wide limits and the resulting alloys being adaptable to uses as varied. It is the common observation that with an increase in the content of copper the color becomes more golden and at the same time the malleability and softness of the alloy are increased. With successive additions to the content of zinc the color becomes lighter and lighter, finally shad ing into a grayish-white, while the alloys be come more fusible, brittle and, at the same time, harder. In other words, the properties of the alloys produced in this way are different; and of course their cost of production varies also, the price of brass decreasing as the con tent of copper becomes less. But this is not the whole story of the adaptability of brass—the characteristic which explains the wide range of its uses at the present time. As a brief summary of the results attained in the course of very extensive researches that have been made in regard to the behavior of alloys of copper and zinc, the following statement has special value and interest: "An alloy contain ing from 1 to 7 per cent of zinc still shows the color of copper, or at the utmost only a slight yellow tinge. With 7.4 to 13.8 per cent of zinc, the color of the alloy undergoes a considerable change," becoming what is described as ea pleasant red-yellow." A pure yellow appears as a characteristic of alloys with 13.8 per cent to 16.6 per cent of zinc, while the color of alloys in which the content of zinc runs up to 30 per cent is also yellow but not pure. "It is a singular fact that with a content of over 30 per cent of zinc a red color appears again, which is most pronounced with equal parts by weight of the metals, an alloy of 50 parts of copper and 50 of zinc having almost a golden color but exhibiting also a high degree of brittleness. With a still higher content of zinc the gold color rapidly decreases, becoming red dish-white with 53 per cent, yellowish-white with 56 per cent and bluish-white with 64 per cent. With a still higher content of zinc the alloy acquires a lead color." Obviously, then, the term "brass" designates an extensive group of alloys. The great variety or diversity of brass objects may occasion less surprise if this circumstance is kept in mind; nevertheless such diversity remains one of the striking illustra tions of modern industrial ingenuity. Thus, as a few of the subdivisions under which the numberless brass objects are classified, we may mention the following: Andirons, badges, balls, barrels, hearings, bedsteads, bolts and nuts, boxes, brackets, buckles, buttons, candelabra, candlesticks, chains, checks, couplings, craft tools, curtain rings, easels, escutcheons, faucets, files, fountains, hammers, handles, hinges, hods, hooks, kettles, knobs, labels, lamps, medals, mouldings, nails, oilers, pins, pipe, plugs, poles, pulpits, pumps, railings, rings, rivets, racks, rods, screens, screws, shells (ordnance, rifle, shot-gun, torpedo, etc.), signs, springs, stamps, tablets, tacks, tags, thimbles, tubes, valves, vases, wire and wire-cloth. Utility is the character istic appearing most plainly in this list; and although, if the list were extended, it would include a large number of architectural and sculptural objects, we should find included in it, on the other hand, a much larger number of purely utilitarian objects — things designed for common use and produced in very great or commercially adequate numbers in which the art quality is a minor consideration if, indeed, it is present at all.
The conclusion is, therefore, in respect to present-thy tendencies, that specialization of utilitarian manufactures characterizes the brass industry, just as in the bronze industry the leaning is toward sculptural and architectural specialization — the architectural products hav ing, as a rule, marked decorative and artistic qualities. Contributory to this specialization of bronze is the circumstance that the copper-and tin alloy stands the action of the weather bet ter than the copper-and-zinc alloy, and this of course influences the choice of material for monumental sculptures, the external portions of architectural designs, etc. In this field brass is, indeed, sometimes a convenient substitute; the superiority of bronze, however, for out door use is generally conceded. Even more important is a peculiarity of bronze that has been described by Mr. William Donald Mitchell in The Art of the Bronze Founder' (New York 1916) as follows: "I wish to call your attention to a wonderful property that bronze possesses and that no other material or sub stance possesses so far as I know. I mean the peculiarity of bronze taking on beautiful colors when subjected to the action of chemicals. Now, you know the color of gold never changes. Silver will oxidize black but chemicals will not cause permanent colors to appear on silver. If you apply acids or any chemical or even water to iron, there isjust one result —a red rust. But the surface of bronze reacts to chem icals applied in a certain manner as an autumn leaf does to frost. Skilled workmen called bronzers easily obtain colors which are as beautiful as those seen on the bronze works of art of antiquity. The color on ancient bronzes is called 'patina,' which means the color or incrustation which age gives to bronze works of art, but the word 'patina' is now generally used to describe the color on modern bronze sculptures. . . . People have said to me that they always thought bronze was the same color as the surface color 'all the way through.' This was a very natural mistake, for it is not often that one sees the natural gold color of bronze, and it is easily understood why people should suppose that the dark bronze they saw was the same color all the way through. . . . The color on bronze is an oxidization of the surface only. It is a film of color on the sur face of the bronze, but is also a part of the bronze itself — like the color on the surface of a piece of glazed pottery. Now, this oxidiza tion on the surface of the bronze does not con tinue eating into the metal until the metal is entirely consumed, as the rust of iron does, but the surface of the bronze having become colored it goes no deeper; and no matter how many years roll by—yes, or centuries—the glowing golden color of the bronze will show if the surface is abraded or scratched. Thus bronze, being practically everlasting, is some times called 'the eternal.' x' According to the best opinion to-day among bronzeworkers, a thin casting (of statues, busts, etc., which are always cast hollow) is to be regarded as an evidence of good foundry work; and modern practice conforms to the view that a successful bronze cast of a sculptured model cannot be made if the alloy exceeds three eighths of an inch in thickness. The standard thickness (or thinness) is from one-quarter of an inch to three-eighths of an inch. The rea sons for this are, that a thin shell of the alloy cools and sets immediately after filling the mold; that an excessive thickness of metal neither makes the casting stronger nor adds to its durability, and. that, if there were too great thickness, the alloy would not harden or set for a considerable time and in the slow cooling would set up strains and shrinkages which would disturb the surfaces of the mold to such an extent that there would be a loss of fine detail.