Rub the dial with a mixture of silver chloride, tartar, and sea-salt, and afterwards rub off the saline matter with water. This silvering is not durable, but it may be improved by heating the article, and repeating the operation, once, or oftener if thought necessary.
The principal difficulties in plating copper ingots are, to bring the surfaces of the copper and silver into fusion at the same time, and to prevent the copper from scaling; for which purposes fluxes are used. The surface of the copper on which the silver is to be fixed must be made flat by filing, and should be left rough. The silver is first annealed, and afterwards pickled in weak spirit of salt; it is planished, and then scraped on. the surface to be fitted on the popper. These prepared surfaces are anointed with a solution of borax, or strewed with fine powdered borax itself, and then confined in contact with each other by binding wire. When they are exposed to a sufficient degree of heat, the flux causes the surfaces to fuse at the same time, and when cold they are firmly united. Copper may likewise be plated by heating it, and burnishing leaf silver upon it; so may iron and brass.
(a) 10 gr. pure silver nitrate to 1 oz. distilled water; add carefully, drop by drop, strong ammonia, until the brown precipitate is redis-solved. When adding the ammonia, keep stirring with a glass rod. in another bottle make a solution of 10 gr. pure crystallised Rochelle salt to 1 oz. distilled water; then, when you have all ready, pour on sufficient to cover all the glass, using two-thirds of the silver solution, and one-third of the Rochelle salt. The mirror can be prepared well by cleaning it with a little wet rouge, and polished dry with a wash-leather; then warm the glass before the fire, or by letting it lie in the sun, to about 70-80° F. Pour on the solution as described above, and let it stand in the warm sunshine 1/2-1 hour. When silvered, pour on it some clean soft or distilled water, and, while still wet, wipe it very gently all over with a little soft wadding, wet; this will take off all the roughness, so that it will take but little rubbing with the rouge leather to polish it.
When perfectly dry, it is easily rubbed up to an exquisite polish.
(6) Cheap Looking-Glasses
Place a sheet of glass, previously washed clean with water, on a table, and rub the whole surface with a rubber of cotton, wetted with distilled water, and afterwards with a solution of Rochelle salts in distilled water, 1 of salt to 200 of water. Then take a solution, previously prepared by adding silver nitrate to ammonia of commerce; the silver being gradually added until a brown precipitate commences to be produced; the solution is then filtered. For each square yard of glass take as much of the above solution as contains 20 grm.
(about 309 gr.) silver, and to this add as much of a solution of Rochelle salt as contains 14 grm. salt, and the strength of the latter solution should be so adjusted to that of the silver solution that the total weight of the mixture above mentioned may be 60 grm. In a minute or two after the mixture is made it becomes turbid, and it is then immediately to be poured over the surface of the glass, which has previously been placed on a perfectly horizontal table, but the plate is blocked up at one end, to give it an inclination about 1 in 40; the liquid is then poured on in such a manner as to distribute it over the whole surface without allowing it to escape at the edges. When this is effected, the plate is placed in a horizontal position at a temperature of about 68° F. The silver will begin to appear in about 2 minutes, and in 20-30 minutes sufficient silver will be deposited. The mixture is then poured off the plate, and the silver it contains is afterwards recovered. The surface is then washed four or five times, and the plate is set up to dry.
When dry, the plate is varnished, by pouring over it a varnish composed of gum dammar, 20 parts; asphalt or bitumen, 5; gutta-percha, 5; and benzine, 75. This varnish will set hard on the glass, and the plate is then ready for use.
A mixture is made of 1 oz. coarsely pulverised silver nitrate, 1/2 oz. spirits of hartshorn, and 2 oz. water, which, after standing for 24 hours, is filtered, the deposit upon the filter, which is silver, being preserved, and an addition is made thereto of 3 oz. spirits of wine, at 60° above proof, or naphtha; 20-30 drops oil of cassia are then added; and, after remaining for about 6 hours longer, the solution is ready for use. The glass to be silvered with this solution must have a clean and polished surface; it is to be placed in a horizontal position, and a wall of putty or other suitable material is formed around it, so that the solution may cover the surface of the glass to the depth of 1/8 - 1/4 in. After the solution has been poured on the glass, 6-12 drops of a mixture of oil of cloves and spirits of wine, in the proportion of 1 part, by measure, oil of cloves to 3 of spirits of wine, are dropped into it at different places; or the diluted oil of cloves may be mixed with the solution before it is poured upon the glass; the more oil of cloves used, the more rapid, will be the deposition of the silver; but the operation should occupy about two hours.
When the required deposit has been obtained, the solutionis poured off; and as soon as the silver on the glass is perfectly dry, it is varnished with a composition formed by melting together equal quantities of beeswax and tallow. The solution, after being poured off, is allowed to stand for 3-4 days, in a close vessel, as it still contains silver, and may be again employed after filtration, and the addition of a sufficient quantity of fresh ingredients to supply the place of those which have been used. About 18 gr. silver nitrate are used for each square foot of glass; but the quantity of spirit varies somewhat, as its evaporation depends upon the temperature of the atmosphere, and the duration of the process. By the addition of a small quantity of oil of carraway or thyme, the colour of the silver may be varied. The oil of cassia purchased of different manufacturers varies in quality; therefore on being mixed with the solution it must be filtered previous to use.