A possible recipe is composed of one hundred parts, by weight, of copper of the purest quality; 14 of zinc or tin; 6 of magnesia; 3/6 salt ammoniac, limestone and cream of tartar. The copper is first melted, then the magnesia, salt ammoniac, limestone and cream of tartar in powder are added separately and gradually. The whole mass is kept stirred for a half hour, the zinc being dropped in piece by piece, the stirring being kept up till they melt. Finally the crucible is covered and the mass is kept in fusion 40 minutes and, the same being removed, the metal is poured into molds, and then is ready for use. The alloy thus made is said to be fine grained, malleable, takes a high polish, and does not easily oxidize.
Other alloy is named Nuremberg Gold and is used for making cheap gold ware, and is excellent for this purpose, as its color is exactly that of pure gold, and does not change in the air. Articles made of Nuremberg Gold need no gilding, and retain their color under the hardest usage; even the fracture of this alloy shows the pure gold color. The composition is usually 90 parts of copper, 2.5 of gold, and 7.5 of aluminum. Manheim gold is composed of copper, zinc, and tin. The proportions are 83.7 parts of copper, 9.3 parts of zinc, and 7.0 parts of tin. The alloy has a fine yellow color, and was formerly much used in making buttons and pressed articles resembling gold. Later alloys however, surpass it in color, and it has fallen somewhat into disuse.
Mosaic gold is composed of 100 parts of copper, and 50 to 55 parts of zinc. It has a beautiful color, closely resembling that of gold, and is distinguished by a very fine grain, which makes it especially suitable for the manufacture of castings which are afterwards to be gilded. The best method of obtaining a thoroughly homogeneous mixture of the two metals is first to put into the crucible one half of the zinc to be used, place the cover upon it, and fuse the mixture under a cover of borax as low a temperature as possible. Have ready the other half of zinc, cut in small pieces and heated almost to melting, and when the contents of the crucible are liquid throw it in, a small portion at a time, stirring constantly to effect as intimate a mixture of the metals as possible.
French Gold when is polished, resembles genuine gold in color that it can be scarcely be distinguished from it. Besides its beautiful color, it has the valuable properties of being very ductile and tenacious, so that it can be easily stamped into any desired shape; it takes a high polish. It is frequently used for the manufacture of spoons and forks. But it is unsuitable for this purpose on account of the large amount of copper contained in it, rendering it injurious to health. Some products have the following composition: 86.21 parts of copper, 31.52 parts of zinc, 0.48 parts of tin, and 0.24 parts of iron.
Pinchbeck was first manufactured in England. Its dark gold color is the best imitation of gold alloyed with copper. Being very ductile, it can easily be rolled out into thin plates, which can be given any desired shape by stamping. It does not readily oxidize and thus fulfills all the requirements for making cheap jewelry which is its main use. The alloy has 88.8 parts of copper and 11.2 parts of zinc.
Palladium gold is composed of copper, gold, silver, and palladium. The alloy has a brownish-red color and are nearly as hard as iron. They are sometimes used for the bearings for the axles of the wheels of fine watches, as they invite little friction and do not rust in the air. The composition is used by Swiss and English watch factories consists usually of gold 18 parts, copper 13 parts, silver 11 parts, and palladium 6 parts.
Talmi Gold is referred to articles of jewelry, chains, earrings, bracelets,, etc., brought from Paris, and distinguished by beauty workmanship, a low price and great durability. Later when this alloy had acquired a considerable reputation, articles were introduced under the same name, but which were really made of other metals, and which retained their beautiful color only as long as they were not used. The fine varieties of Talmi gold were manufactured from brass, copper, or tombac, covered with a thin plate of gold, combined with the base by rolling, under strong pressure. The plates are then rolled out by passing through rollers, and the coating no only acquires considerable density, but adheres so closely to the base that the metal will keep its beautiful appearance for years. Of late, many articles of talmi gold has been introduced whose gold coating is produced by electroplating, and is in many cases so thin that hard rubbing will bring through the color of the base. Such articles, of course, are not durable. In genuine talmi gold, the coating, even though it may be thin, adheres closely to the base, for the reason that the two metals are actually welded by the rolling, and also because alloyed gold is always used, which is harder than pure gold. The pure gold of electroplating is soft. The composition of some varieties of talmi gold are given. It will be seen that gold content varies greatly, and the durability of the alloy will, of course correspond to this.
|
Type |
Copper |
Zinc |
Tin |
Iron |
Gold |
|
1 |
89.9 |
9.3 |
--- |
--- |
1.3 |
|
2 |
90.8 |
8.3 |
--- |
--- |
0.9 |
|
3 |
90.0 |
8.9 |
--- |
--- |
0.9 |
|
4 |
90.7 |
89 |
--- |
--- |
0.5 |
|
5 |
87.5 |
12.4 |
--- |
--- |
0.3 |
|
6 |
93.5 |
6.6 |
--- |
--- |
0.05 |
|
7 |
86.0 |
12.0 |
1.1 |
0.3 |
--- |
The alloys 1, 2 and 3 are genuine Paris Talmi gold; 4, 5 and 6 are electroplated imitations; and 7 is an alloy of wrong composition to which gold does not adhere firmly.
Japanese Alloys. In Japan some specialties in metallic alloys are in use of which the composition is as fallow: Shadke consists of copper with from 1 to 10 percent of gold. Articles made from this alloy are laid in a pickle of blue vitriol, alum, and verdigris, until they acquire a bluish black color. Gui-shi-bu-ichi is an alloy of copper containing 30 to 50 % silver. It has a peculiar gray shade. Mokume consists of several compositions. Thus, about 30 gold foils are welded together with shadke, copper, silver, and gui-shi-bu-ichi and pierced. The pierced holes are, after firmly hammering together the plates, fill up with the above named pickle.