CHAPTER V

GERMAN SILVER

§ 90. The alloys, largely manufactured under this name, consist essentially of nickel, copper, and zinc. Different names are used to signify the same substance, such as: Nickel-Silver, Argentan, Packfong, White-Copper, Weisskupfer, Neu-Silver, and Maillechort. Besides these, dif

ferent manufacturers employ fanciful names to denote alloys containing different proportions of the constituent metals, which they consider best suited to produce a given result, a good white colour being a great desideratum. Thus : Nevada Silver, Virginia Silver, Potosi Silver, Silveroid, Silverite, Electrum, Afénide, Agiroide, etc., are simply German silver; but in some cases a little cobalt is present as well as nickel, and some makers add a small quantity of iron or manganese. 1 to 3 per cent of lead is sometimes

added for cast work.

The properties which make German silver so valuable are its white colour, lustre, hardness, tenacity, toughness, malleability, ductility, and power of resisting certain chemical influences. When carefully prepared it works well under the stamp, and between the rolls, but it is advisable that the metals used in alloying should be as pure as possible, since small quantities of certain impurities, such as arsenic, seriously injure its working qualities. Cobalt frequently accompanies nickel in its ores, and becomes reduced at the same time as that metal, and alloys readily with it; but as the chemical

and physical properties of both metals are closely allied to each other, cobalt does not exert an injurious influence.

Iron has a beneficial effect on German silver for some purposes. It makes the colour whiter, increases the tenacity and elasticity, but makes it harder. In some experiments made by the author, 1 to 2 per cent of iron was found to have no deteriorating effect, except with regard to hardness, and the colour of an alloy containing 12 per cent of nickel was equal to one containing 16 per cent, in which no iron was present, the same quantity of zinc being used in each case. The metal rolled remarkably well. In the better qualities of German silver used for rolling and spinning, iron was found to be injurious, and for these purposes the purer the alloy the better it works. All commercial varieties of German silver contain iron, especially when scrap-metal is used in connection with new metal for the melting charge, the iron being probably obtained from files and other tools. used in the fabrication of the various articles. Packfong, the original nickel alloy introduced from China, contains as much as 3 per cent of iron. Gersdorff states that iron is difficult to alloy with the other constituents, and when that metal is added to fused German silver it does not combine with it, and forms upon the surface of the fused mass a layer, consisting of copper, nickel, and iron. He states that the iron must be previously fused with a portion of the copper, under a layer of charcoal-powder in a blast-furnace, and the alloy formed may then be used to alloy with the nickel, zinc, and the remainder of the copper required. This is quite unnecessary, as proved by the author's experiments, in which copper nickel and the best iron wire were strongly heated together in a covered crucible, and zinc added to the molten contents, then vigorously stirred. The metals were perfectly alloyed together, and no separation of iron could be detected when the ingot was rolled into a thin sheet and highly polished.

The effect of tin when alloyed with German silver to the extent of from 2 to 4 per cent was found much more

injurious than that of iron, the strips being brittle when rolled, and the metal of a decidedly yellow cast when polished. From his experiments the author concludes that there is no advantage in adding tin to German silver, as it impairs the colour, hardens the metal, and makes it brittle. Moreover, tin is an expensive metal, and better effects can be obtained by the use of iron and zinc. An alloy, patented more than fifty years ago, had the following composition :

Silver in certain proportions does not impair the malleability of German silver, but no particular advantage is gained by its use. M. Ruolz many years ago manufactured a series of alloys for jewellery having the following composition :—

By varying the proportions the alloys may be made to resemble silver very closely; but the nickel and copper must be of good quality, or the alloys will be hard, brittle, and difficult to work. It is stated that French jewellers still use these and similar alloys. An old alloy, termed American nickel silver, contains—

Another alloy, having the same advantage of being complex,

which is its chief merit, was introduced by Mr. Toucas, and consists of

According to the inventor, it has nearly the colour of silver, may be worked like it, and laminated by the ordinary processes; it is resisting, susceptible of a fine polish, with the lustre of platinum, and may be silvered perfectly well. He recommends it for objects which are to be spun, hammered, or chased; but for cast and adjusted pieces he prefers to increase the proportion of zinc, in order to increase the fluidity of the metal.

Modern proportions for German silver alloys vary considerably, each manufacturer having a preference for his own particular mixture for any given quality. For metal which is to be rolled, pressed, or stamped, the alloy must be tough and malleable; and as whiteness in colour is an important consideration, it follows that the metals nickel and zinc must be present in considerable quantity in order to overcome the red colour of the copper. For cast work, which only requires to be filed and turned, malleability is not of first importance, it being sufficient if the metal has the requisite tenacity and toughness, and also sufficient liquidity when melted and adaptability to ordinary moulding purposes. Another item, which cannot be ignored, is that of cost, and as nickel is an expensive metal, it is to the advantage of the manufacturer to employ as much zinc as is consistent with the properties enumerated above.

Founders whose specialty is the manufacture of German silver have agreed that the best alloy for beauty, lustre, and working properties consists of the following proportions :

It is also the most costly among similar alloys, on account of the large proportion of nickel present.

§ 91. The alloys most largely employed for spoons, forks, and other table and ornamental goods contain from 6 to 22 per cent nickel; the lower qualities being little better than brass, and only used for the very commonest goods, and the higher qualities approximating to pure nickel in whiteness. In order to determine the best proportions to employ for alloys containing 8, 10, 12, 16, and 20 per cent respectively of nickel the following experiments were made by the author. In all cases the copper and nickel were melted together under a layer of charcoal, and a little borax added as a flux. The zinc was added when the former were well fused; and the whole was well stirred with a wooden rod before pouring the metal into the iron mould. Ordinary commercial metals were employed.

ALLOYS CONTAINING 8 PER CENT NICKEL

No. I was the whitest, but the weakest, and rolled the worst of the series. No. II was whiter than Nos. III or IV, and was the toughest of the four; an experimental ingot about inch thick was bent double in a vice without cracking. It rolled well, but was not so malleable as Nos. III and IV. Nos. III and IV rolled equally well, but No. III was a shade the whiter.

ALLOYS CONTAINING ABOUT 12 PER CENT NICKEL