An assessment of the methods of silver plating used by Elkington and Woolrich in 1850.
The Electro and Magneto Plating form branches of manufacture which essentially belong to Birmingham. It is among the more singular events of the age, that the accidental observation of a deposit, precipitated by the action of the galvanic battery cell, containing sulphate of copper, being a complete copy of such cell. Who would have thought, that the mere dissolving of metals by acid, or the revolving of a wire in front of the poles of a magnet, should be the means of establishing a trade which is useful, most beautiful, and promises to become the most extensive the art of working in metals may have to boast of. The galvanic or electro plating of the Messrs. Elkington and others, and magnetic plating of Mr. J. S. Woolrich, furnishes the means of performing these wonders of science.
The methods of plating and gilding are almost entirely carried on by these processes, and from their enabling the manufacturer to use cast and richly ornamented goods, the style is daily improving over the rigid and stiff forms of the old branch of the plated wares manufacture. By the new methods, articles of any size, shape, or lightness, can be coated with the same cost as the plainest sheet of metal ; consequently we see the manufacturers availing themselves of cast ornaments which they could not do before ; all had to be manufactured from the plated copper, the seams more or less showing the solder used in putting them together ; and when the plate was worn off, Alexander, the coppersmith, necessarily protruded.
The new process enables the manufacturer to make his goods from German silver, an alloy of nickel, which is hard and white, and after the articles are made and polished, they receive the last thing, a coating of the "precious metal" which entirely envelopes the white base ; and the articles cannot then be detected by the eye from that of solid silver, and have the great advantage, when the silver is worn off, of not showing the red copper. The process was accused of peeling off, and want of hardness, which, by subsequent improvements, has been entirely mastered. The process is by means of large wooden vats, which contain a strong solution of silver, in which is placed at convenient distances, sheets of pure silver, connected with a wire, which forms one of the channels for electricity ; and, resting upon the top of the vats, are likewise brass rods, which are connected together by a wire ; after having been well cleaned, the various articles to be plated are suspended from these rods by wires between the sheets ; a current of electricity is sent by the wire to the sheets, through the liquid to the articles, and then along the brass rods back to its source ; the solution suffers decomposition, the silver, of which it is partly composed, is deposited on the articles, while at the same time the silver sheets lose the same amount of silver ; this process goes on as long as required, so that the thinnest film, or the thickest coat, may be obtained ; the goods being weighed before and after the process, shows the amount of metal deposited upon them. The electro, or galvanic plating, is performed by means of galvanic batteries, which are made with plates of zinc, copper, and dilute sulphuric acid ; by the action of the acid upon these metals, electricity is generated ; and which being passed, by the means described, into a solution of cyanide of potassium and silver, the plating is effected. This constitutes the essential part of the patent granted to Messrs. Elkington, in March, 1840, and which they carry on in their extensive works in Newhall Street.
The Magneto Process consists in the novelty of single currents of magnetic electricity, which are generated by simply revolving a coil of wire between the poles of a steel magnet, and is found to answer every purpose of a galvanic battery, without any of its uncertanity of action, expense, or trouble. The same machine admits being regulated in power for the largest or smallest articles. The objection to its use is, that it requires a small, constant power, to turn the coil of wire ; a thing of no moment, where steam, or other power is used ; its regularity of action, however, constitutes one of its chief advantages. The amount of metal deposited is ascertained by the length of time the articles are under operation, and in this respect it is greatly superior to the battery, which is more or less incessant ; and as there are many classes of articles which cannot be weighed, its excellency is self-evident. The solution employed, is sulphate of pottasa and silver ; the deposit from this solution is much harder, and not so liable to tarnish as that from the cyanide. This process is carried on by the patentee at his establishment, 12, James-street, St. Paul's; the patent is dated August, 1842. Licenses have been granted under these patents to several manufacturers, but it is found that the process is more cheaply and better carried on, on a large scale. Establishments, therefore, have been opened where individuals can send their work to be plated and gilt. Another great superiority over the old mode of manufacturing plated wares is, when the silver may be worn off, they can be re-plated at a moderate expense. Another application of electricity consists in the deposition of metals upon wax casts, which, when melted out, leaves the precise form in metal; this process is known under the name of Electrotype, and which at some future period will be of immense moment to the manufacturers.
Source: History, Gazetteer, and Directory, of Warwickshire
By Francis White & Co.--1850
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