3707. To Silver-plate Large Articles

3707.    To Silver-plate Large Articles (such as those plated in factories), it is not always sufficient to dip them in nitric acid; wash and immerse them in the solution, in order to effect a perfect adhesion of the two metals. To secure this, a small portion of quicksilver is dissolved in nitric acid, and a little of this solution is added to water, in sufficient quantity to enable it to give a white silvery tint to a piece of copper when dipped into it; the article then, whether made of copper, brass, or German silver, after being dipped in the nitric acid and washed, is dipped into the nitrate of mercury solution till the surface is white; it is then well washed by plunging it into two separate vessels containing clean water, and finally put into the plating solution. This secures perfect adhesion of the metals. One ounce of quicksilver thus dissolved will do for a long time, though the liquor is used every day. When the mercury in this solution is exhausted, it is liable to turn the article black upon being dipped into it; this must be avoided, as in that case it also causes the deposited metal to strip off.

3708. To Preserve the Dead, Matted Appearance of Silver after Electroplating'

3708.    To Preserve the Dead, Matted Appearance of Silver after Electroplating'. If it is desired to preserve the surface in this condition, the article must be taken out of the electroplating solution, care being taken not to touch it by the hand, and immersed in boiling distilled water for a few minutes. On being withdrawn, sufficient heat has been imparted to the metal to dry it instantly. If it is a medal, it ought to be put in an air-tight frame immediately, or if a figure, it may be at once placed under a glass shade, as a very few days' exposure to the air tarnishes it, by the formation of sulphuret of silver, especially in a room where there is fire or gas.

3709. To Remove the Chalky Appearance of Silver afterPlating

3709.     To Remove the Chalky Appearance of Silver afterPlating. When articles are taken out of the electroplating solution they are swilled in water, and then put into boiling water. They are afterwards put into hot sawdust, which dries them perfectly. Their color is chalk-white. They are generally weighed before being scratch-brushed; that is, brushed with fine wire brushes {see Nos. 3381 (To Frost Watch Movements) and 3706), and old ale, beer, or water containing in solution a little gum, glue, or sugar, but the amateur may use a hard hair brush. It may be afterwards burnished according to the usual method of burnishing, by rubbing the surface with considerable pressure with polished steel or the mineral termed bloodstone. Although this operation does not displace any of the silver, still, in taking off the chalky appearance, there is a slight loss of weight. The appearance after scratching is that of bright metallic silver.

3710. To Increase the Brightness of the Deposit

3710.    To Increase the Brightness of the Deposit. A little sulphuret of carbon added to the plating solution prevents the chalky appearance, and gives the deposit the appearance of metallic silver; the reaction which takes place in this mixture is not yet understood. The best method of applying the sulphuret of carbon is to put one or two ounces into a largo bottle, then fill it with strong silver solution having an excess of cyanide of potassium, and let it repose for several days, shaking it occasionally. A little of this silver solution is added, as required, to this plating solution, which will give the articles plated the same appearance as if scratched. It is also found that the presence of sulphuret of carbon prevents the solution from going out of order; indeed, we have seen a solution that has been constantly working from two to three years, while, generally, they were subject to go out of order for a time, in less than one year - although, after standing a time, they would recover - but these are curious reactions not yet investigated.