The color of the deposit may be regulated in quite a number of ways, pure gold having too light a color to be admired by many. An old solution, in which a great many copper articles have been plated, is capable of yielding different colored deposits by means of regulating the size of the anodes, temperature of the solution, the strength of the battery, and, in a degree, the strength of the solution also.
An old solution, that yields a pale yellow deposit, when but a small portion of the anode touches the solution, will yield a darker deposit when the anode is further immersed, and finally, when it is entirely immersed, the deposit will be of a red color.
The temperature of the solution effects the color of the deposit, it being much darker and richer when the solution is used hot than when it is used cold, and it is claimed by a great many electro-platers, and justly too, that a
metal deposited from a warm solution is harder, and consequently more durable, than a metal deposited from a cold solution.
The strength of the battery also has a great deal to do with the color of the deposit, a moderately weak current producing a much lighter colored deposit than that produced by a much stronger battery. There are, however, certain limits regulating both the temperature and battery power, beyond which it is not safe to venture. The temperature should never be allowed to greatly exceed i6o° Fahr.
The amount of battery power is a more difficult matter to determine, as it varies with the amount of surface presented by the articles to be plated. Generally speaking, three cups of the ordinary Callaud or gravity battery will be amply sufficient for operations on the larger scale, while one, or, perhaps, two cups will answer for the gilding of small articles, or electro-plating on a small scale.
Gold deposited by the electric current is not always pure gold, as other metals are often deposited with it in order to produce the desired color or tint, and in large electro plating establishments, or where a great variety of work is done, a number of gilding solutions are used, each of them yielding a different colored deposit. However, one solution is capable of yielding, with careful and judicious management, a deposit of gold varying in color from the light yellow of almost pure gold, to a deposit so alloyed with copper as to resemble 14 karat gold, and which it really is.
In order to accomplish this, the solution must contain a small amount of copper. This metal is always present in old gilding solutions, caused by a very minute portion of the metal being dis¬solved from each article of copper that has been plated in the solution. Of course the amount of metal dissolved from each individual article is very small indeed, but when in the course of time a great many of them have been plated, the aggregate of the dissolved copper is con¬siderable, and quite sufficient to change the color of the deposit. A freshly made solution used quite hot, with a large gold anode and a toler¬ably strong battery, will generally give a satis¬factory deposit, but should it still be of too light a color, remove the gold anode and substitute in its place a clean one of copper and work the solution with it until the deposit begins to slightly change its color, and then replace it with the gold anode. If the copper anode has been weighed before, and again just after using it, as above mentioned, it will be discovered that a portion of it has been dissolved in the solution, which by being deposited with the gold gives it a richer and darker color.
To obtain a green colored deposit, add a small quantity of the ordinary silver plating solution to the gilding solution, with gentle stirring, taking care to add just enough to produce the desired effect, as where too much of the silver solution is added it is liable to spoil it.
White gilding is produced by adding a solution of nitrate of silver to the gilding solution, until the desired colored deposit is obtained, which must be ascertained by actual trial.
Pink gold is obtained by first plating the articles in a cold and weak solution, with a weak battery, then giving them another coat in a hot and strong solution that has considerable copper in it, using a more powerful battery in order to obtain a dark colored deposit, then give them an exceedingly thin coating in the ordinary silver plating solution, and finally burnish them. The coating of silver should be barely sufficient to
5 impart a lighter tinge to the deposit which, if the operation has been successful, will be of a beautiful pink color when burnished.
To gild the inside surface of articles, such as cups, cream pitchers, and similar articles, fill them with the solution, and suspend a gold anode in them, and attach the article itself to the wire leading from the zinc pole of the battery. The lips of the pitcher, and other portions that the solution does not touch, may be plated by laying a rag wetted with the gilding solution upon the part, leaving a portion of it immersed in the solution contained in the vessel. The outside surface of the article, or that portion of it you may not want to gold plate, may be coated with a solution of sealing wax dissolved in naptha, or simply painted over with melted beeswax, and the articles placed in the gilding solution in the ordinary way, and after the gilding operation has been completed, the wax is easily removed.
Hiç yorum yok:
Yorum Gönder