pintthere are obtained, according to the duration of the immersion, yellowish, orange, rosy, then bluish shades. Upon polarizing the ebullition the blue tint gives way to yellow, and finally to a pretty gray. Silver, under the same circumstances, becomes very beautifully colored. After a long ebullition in the following solution we obtain a yellow-brown shade, and then a remarkable fire red:
| Chlorate of potash | 75 grains |
| Carbonate of nickel | 30 grains |
| Salt of nickel | 75 grains |
| Water | 16 ounces |
The following solution gives a beautiful, dark-brown color:
| Chlorate of potash | 75 grains |
| Salt of nickel | 150 grains |
| Water | 10 ounces |
The following gives, in the first place, a red, which passes to blue, then to pale lilac, and finally to white:
| Orpiment | 75 grains |
| Crystallized sal sodæ | 150 grains |
| Water | 10 ounces |
The following gives a yellow brown:
| Salt of nickel | 75 grains |
| Sulphate of copper | 75 grains |
| Chlorate of potash | 75 grains |
| Water | 10 ounces |
On mixing the following solutions, sulphur separates and the brass becomes covered with iridescent crystallizations:
| I.— | Cream of tartar | 75 grains |
|---|---|---|
| Sulphate of copper | 75 grains | |
| Water | 10 ounces | |
| II.— | Hyposulphite of soda | 225 grains |
| Water | 5 ounces |
Upon leaving the brass objects immersed in the following mixture contained in corked vessels they at length acquire a very beautiful blue color:
| Hepar of sulphur | 15 grains |
| Ammonia | 75 grains |
| Water | 4 ounces |
Miscellaneous Coloring Of Brass.
—Yellow to bright red: Dissolve 2 parts native copper carbonate with 1 part caustic soda in 10 parts water. Dip for a few minutes into the liquor, the various shades desired being obtained according to the length of time of the immersion. Green: Dissolve 1 part copper acetate (verdigris), 1 part blue vitriol, and 1 part alum in 10 parts of water and boil the articles therein. Black: For optical articles, photographic apparatus, plates, rings, screws, etc., dissolve 45 parts of malachite (native copper carbonate) in 1,000 parts of sal ammoniac. For use clean and remove the grease from the article by pickling and dip it into the bath until the coating is strong enough. The bath operates better and quicker if heated. Should the oxidation be a failure it should be removed by dipping into the brass pickle.
A verdigris color on brass is produced by treating the articles with dilute acids, acetic acid, or sulphuric acid, and drying.
Brown in all varieties of shades is obtained by immersing the metal in solutions of nitrates or ferric chloride after it has been corroded with dilute nitric acid, cleaned with sand and water, and dried. The strength of the solutions governs the deepness of the resulting color.
Violet is caused by immersing the thoroughly cleaned objects in a solution of ammonium chloride.
Chocolate color results if red ferric oxide is strewn on and burned off, followed by polishing with a small quantity of galena.
Olive green is produced by blackening the surface with a solution of iron in hydrochloric acid, polishing with galena, and coating hot with a lacquer composed of 1 part varnish, 4 parts cincuma, and 1 part gamboge.
A steel-blue coloring is obtained by means of a dilute boiling solution of chloride of arsenic, and a blue one by a treatment with strong hyposulphite of soda. Another formula for bluing brass is: Dissolve 10 parts of antimony chloride in 200 parts of water, and add 30 parts of pure hydrochloric acid. Dip the article until it is well blued, then wash and dry in sawdust.
Black is much used for optical brass articles and is produced by coating with a solution of platinum or auric chloride mixed with nitrate of tin.
Coloring Unpolished Brass.
—A yellow color of handsome effect is obtained on {129} unpolished brass by means of antimony-chloride solution. This is produced by finely powdering gray antimony and boiling it with hydrochloric acid. With formation of hydrogen sulphide a solution of antimony results, which must not be diluted with water, since a white precipitate of antimony oxychloride is immediately formed upon admixture of water. For dilution, completely saturated cooking-salt solution is employed, using for 1 part of antimony chloride 2 parts of salt solution.
Coloring Fluid For Brass.
—Caustic soda, 33 parts; water, 24 parts; hydrated carbonate of copper, 5.5 parts.
Dissolve the salt in water and dip the metal in the solution obtained. The intensity of the color will be proportional to the time of immersion. After removing the object from the liquid, rinse with water and dry in sawdust.
Black Color On Brass.
—A black or oxidized surface on brass is produced by a solution of carbonate of copper in ammonia. The work is immersed and allowed to remain until the required tint is observed. The carbonate of copper is best used in a plastic condition, as it is then much more easily dissolved. Plastic carbonate of copper may be mixed as follows: Make a solution of blue vitriol (sulphate of copper) in hot water, and add a strong solution of common washing soda to it as long as any precipitate forms. The precipitate is allowed to settle, and the clear liquid is poured off. Hot water is added, and the mass stirred and again allowed to settle. This operation is repeated six or eight times to remove the impurities. After the water has been removed during the last pouring, and nothing is left but an emulsion of the thick plastic carbonate in a small quantity of water, liquid ammonia is added until everything is dissolved and a clear, deep-blue liquid is produced. If too strong, water may be added, but a strong solution is better than a weak one. If it is desired to make the solution from commercial plastic carbonate of copper the following directions may be followed: Dissolve 1 pound of the plastic carbonate of copper in 2 gallons of strong ammonia. This gives the required strength of solution.
The brass which it is desired to blacken is first boiled in a strong potash solution to remove grease and oil, then well rinsed and dipped in the copper solution, which has previously been heated to from 150° to 175° F. This solution, if heated too hot, gives off all the ammonia. The brass is left in the solution until the required tint is produced. The color produced is uniform, black, and tenacious. The brass is rinsed and dried in sawdust. A great variety of effects may be produced by first finishing the brass before blackening, as the oxidizing process does not injure the texture of the metal. A satisfactory finish is produced by first rendering the surface of the brass matt, either by scratch-brush or similar methods, as the black finish thus produced by the copper solution is dead—one of the most pleasing effects of an oxidized surface. Various effects may also be produced by coloring the entire article and then buffing the exposed portions.
The best results in the use of this solution are obtained by the use of the so-called red metals—i.e., those in which the copper predominates. The reason for this is obvious. Ordinary sheet brass consists of about 2 parts of copper and 1 part of zinc, so that the large quantity of the latter somewhat hinders
