The lobster red of the Japanese is, I believe, not a product of pickling at all, but is cuprous oxide, formed by heating capper in air (it may be in air and steam, as is the case with their well-known and brilliant coloured commercial samples of metal), and then burnishing it, but 1 om not certain about it.
The Americans have produced some very beautiful alloys which show a rich purple tint. They are apparently of silver, and running over the object, usually small, is a damask pattern in a darker shade of the same purple line. This beautiful damask-like ornament is produced apparently by inlay, yet it is not possible to see that there is any inlay. 1 believe the patina in this particular case is in some way produced by the action of light.
Many of these alloys may be blended by casting; yon may have an alloy with a solidifying point a little lower than the rest, and pour the two alloys in succession, and the one which sets first may be covered by the other one. Take for example a bronze god clothed in brass, with brans anklets and bracelets. That is done by pouring brass round a copper casting of suitable form. Endless modifications may be produced in this way by pouring alloys one over the other. (Prof. Roberts-Austen.) Colouring Metal Warea. - Small metallic articles, buttons, clasps, buckles, and others, have different coloured films produced on them by various methods. Some of these are known as oxidised silver. Rainbow colours are produced on brass buttons by stringing them on a copper wire and dipping them in a bath of plumbate of soda freshly prepared by boiling litharge in caustic soda, and pouring it into n porcelain dish. A linen bag of finely pulverised litharge or hydiated oxide of lead is suspended in the solution, so as to keep up the original strength of the solution. While the buttons are in the solution, they are touched one after the other with a platinum wire connected with the positive pole of a battery, until the desired colour appears. The galvanic current employed must not be too strong.
The colours are more brilliant if they are heated after they have been rinsed and dried Coloured films are more conveniently produced upon bright brass by different chemicals, by painting with them, or by immersion. For example: Golden yellow. - By dipping in a perfectly neutral solution of acetate of copper. Dull grayish green. - Repeatedly painting with very dilute solution of chloride of copper. Purple. - Heating them, and rubbing over with a tuft of cotton saturated with chloride of antimony. Golden red. - A paste of four parts of prepared chalk and mosaic gold.
Japanese knife socket.
In covering an article with any coloured bronze in powder, it is first rubbed with a very little linseed oil, and the bronze is dusted evenly over it from a dust bag. It is afterwards heated in an iron pan to about 480° F. In recent times small articles are also roughened by dipping in strong nitric acid, and, after washing and drying, they are coated with a rapidly drying alcohol varnish that has been coloured yellow with picric acid, red with fuch-sine, purple with methyl violet, or dark blue with an aniline blue. This gives the desired colour with a beautiful metallic lustre. These colours are not very durable and are for inferior goods.