Copper-Plating on Zinc.
Take an organic salt of copper—for instance, a tartrate. Dissolve 126 grammes sulphate of copper (blue vitriol) in two litres of water; also 227 grammes tartrate of potash and 286 grammes crystallized carbonate of soda in 2 litres of water. On mixing the two solutions, a light bluish-green precipitate of tartrate of copper is formed. It is thrown on a linen filter and afterwards dissolved in half a litre of caustic soda solution of 16° B. when it is ready for use.
The coating obtained from this solution is very pliable, smooth and coherent, with a fine surface; acquires any desired thickness if left long enough in the bath.
Other metals can also be employed for plating, in the form of tartrates. Instead of tartrates, phosphates, oxalates, citrates, acetates and borates of metals can be used; so that it seems possible to entirely dispense with the use of cyanide baths.
To Transfer Engravings To Mother-of-Pearl.
To transfer engravings to mother-of-pearl, coat the shell with thin white copal varnish. As soon as the varnish becomes sticky, place the engraving face down on it, and press it well into the varnish. After the varnish becomes thoroughly dry, moisten the back of the engraving and remove the paper very carefully by rubbing. When the paper is all removed and the surface becomes dry, varnish lightly with copal.
Metal for Stereotyping.
For every six pounds of lead add one pound of antimony. The antimony should be broken into very small pieces, and thrown on the top of the lead when it is at red heat. It is a white metal, and so brittle that it may be reduced to powder; it melts when heated to redness; at a higher heat it evaporates.
The cheapest and most simple mode of making a stereotype metal is to melt old type, and to every fourteen pounds add about six pounds of grocer’s tea-chest lead. To prevent any smoke arising from the melting of tea-chest lead it is necessary to melt it over an ordinary fire-place, for the purpose of cleansing it, which can be done by throwing in a small piece of tallow about the size of a nut, and stir it briskly with the ladle, when the impurities will rise to the surface, and can be skimmed off.