The best way to restore the original lustrous whiteness of silver goods, lost or impaired by exposure to sulphurous atmospheres or by having been often and perhaps carelessly cleaned, is first to anneal and then to pickle the silver, the latter portion of the process resembling the colouring of gold alloys. The annealing may be done in a charcoal fire or in the flame of a gas or oil blowpipe; the heat destroys all organic matter adhering to the surface of the article, at the same time oxidising on the surface the base metals with which the silver is alloyed. The annealing requires some care and attention, or else the workmanship of the piece will be lost. If the silver has been soft-soldered previously, it is unfit to be annealed, as the heat necessary for this would melt the solder. It is necessary to remove all stones, steel, or any material not silver or liable to be injured by the heat, and it is also advisable to remove pins, tongues, or other steel work from brooches, etc. Over- or under-heating must be prevented; in the former case, if the article is overheated, the silver is liable to melt; and if under-heated, the adhering organic matter is not effectually destroyed, and the surface not sufficiently oxidised.
In order to obtain the required degree of heat, and not to run a risk either cf under- or over-heating, the article is held with a pair of pincers very close over the flame of the lamp so as to be covered with soot all over, and is then exposed to the blast of a flame by means of a blowpipe until the soot burns or disappears. When the article is cool, it is immersed in a boiling solution of from 1 part to 5 parts of sulphuric acid in about 20 parts of water. The quantity of the water depends upon the quality of the silver; the coarser this is, the stronger is the solution. The solution dissolves the extracted deposit of oxide and leaves a coating of fine silver on the surface. Good sterling silver will be whitened almost in an instant, common silver will take a minute or even longer; if the articles are left too long in the solution, they turn an unseemly greyish colour, and the process has to be repeated. Common silver has to be treated repeatedly in this manner before the desired whiteness is obtained, and in some cases even will have to be silvered by electro-plating. As soon as the article in the acid turns white it is transferred quickly to lukewarm water. The articles are then dried in sawdust, kept in an iron vessel near the stove or in any warm place.
Any places on the article desired to look bright are burnished with a steel burnisher. Silver merely oxidised by exposure to the atmosphere, and not by repeated cleaning, is restored simply by brushing with a clean tooth brush and a little carbonate of soda.