Knight's Mechanical Encyclopedia, S., Sil′ver-ing.

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19th-Century American

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Sil′ver-ing.

Covering the surface of baser metal or other material with silver. When the silver is in the form of leaf, the operation is analogous to that of gilding (which see).

In the plating of metals, the principal steps are the following:—

The smoothing down and polishing the surface of the plate to be silvered.

Annealing. Heating the plate red hot and plunging it into dilute nitric acid until perfectly clean.

Pumicing. Cleaning the surface with pumice-stone and water.

Warming. Heating until the plate slightly hisses, when it touches water, after which it is dipped in dilute nitric acid, causing a slight roughness of the surface, which retains the silvering.

Hatching. When the surface is not thus rendered sufficiently rough, it is gone over with a graving tool; chased surfaces, however, need not be touched.

Blueing. Heating the piece until its surface assumes a bluish tint.

Charging. The workmen's term for silvering. The leaves of silver are placed on the piece while heated, and fixed to its surface by a burnisher. The workman operates on two pieces at once, so that while he is applying the leaf to one the other is being heated.

After applying two silver leaves, the piece is heated to the same degree as at first, and four more leaves are then laid on with the burnisher. He thus applies the leaves successively one over another until the required thickness is attained, and afterward burnishes the surface with a strong pressure.

In silvering with precipitated chloride of silver, a solution of common salt is added to a solution of nitrate of silver, and the resulting white mass is washed and dried; 1 part of this powder is mixed with 3 of good pearlash, 1 of washed whiting, and 1 1/2 sea salt. After cleaning the surface of the brass, it is rubbed with soft leather or cork, moistened with water and dipped into the above powder. After silvering, the surface is washed with water, dried, and varnished. Some use a mixture of 1 part of the silver precipitate with 10 of cream of tartar.

Inferior plated buttons are silvered with a mixture of 1 ounce corrosive sublimate, 3 pounds common salt, and 3 pounds sulphate of zinc made into a paste with water; this is smeared over the buttons, which are then heated to expel the mercury, and afterward burnished.

Leather is silvered by applying a coating of parchment-size or spirit-varnish, and afterward coating with silver-leaf under pressure.

The silvering of glasses and mirrors by the electro-plating process is accomplished in the bath of silver solution in the usual way, the glass being perfectly clean. See next article. See also Platinizing, page 1741; looking-glass, pages 1350, 1351; Mir-Ror, pages 1452, 1453; glass-silvering, pages 982, 983.

1877.

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Knight's Mechanical Encyclopedia
Knight, Ed.

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Sil′ver-ing.

Knight's Mechanical Encyclopedia Knight, Ed.

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Table of Contents:

Sil′ver-ing.

Knight's Mechanical Encyclopedia
Knight, Ed.