There are many recipes for obtaining various color effects upon copper, some of which are expensive and difficult to handle, and others require considerable skill in their application. Some of the standard and easily applied (simple immersion) coloring solutions for use on copper are as follows:
No. 1. Antique or Oxidized Copper. Dissolve about one cubic inch of potassium sulphide in one pint of water, add six drops of ammonia, and apply to the copper; if the color is too dark add more water. When it is dry, polish with emery cloth in one direction only to relieve the color and bring out the design; then lacquer or wax.
No. 2. Another antique finish on copper that gives a more varigated color effect is as follows: In one pint of water dissolve one-fourth of a teaspoonful of barium sulphide. Clean the article thoroly and wash in cold water; while it is still wet apply the barium sulphide solution. Various results can be obtained by making the solution weaker or stronger. When it is dry finish by lacquering or waxing.
No. 3. Brown color on copper, shading to black according to strength of solution: in one pint of water dissolve five drachms of nitrate of iron.
No. 4. Potassium sulphide, three ounces; ammonia, one-half ounce; water, one gallon. Immerse the articles.
No. 5. Dark brown on copper: one pint of water, five drachms of nitrate of iron, and two drachms of potassium sulphoeyanide.
No. 6. Brown on copper: dissolve one ounce of sal ammoniac and one-third of an ounce of oxalate of potash in one-half pint of vinegar. Immerse and apply with a cloth.
No. 7. Dark brown: in one pint of water dissolve one ounce of sulphate of copper, one ounce of hyposulphate of soda, two drachms of hydrochloric acid.
No. 8. Red shading to brown, according to strength of solution : in one pint of water dissolve one drachm of pearl ash. and one drachm of sulphur.
No. 9. Red: one pint of water, two drachms of sulphide of arsenic, one ounce of pearl ash.
No. 10. Steel gray: in one pint of water dissolve one drachm of chloride of arsenic. Bring the solution nearly to the boiling point and immerse the articles in it.
No. 11. Various colors may be obtained by means of the following solution: dissolve in one quart of water three hundred grains of acetate of lead, and six hundred grains of hyposulphite of soda. After the solution is dissolved, heat to the boiling point and immerse the articles. The first color produced is gray, continued baths will produce violet, maroon, red, and finally steel blue.
No. 12. There is also the very interesting method of coloring copper by heat. In this method no chemicals of any kind are used; all that is necessary is that the metal shall be perfectly clean and that it be slowly passed to and fro thru a blue gas flame, such as is obtained from a bunsen burner or any ordinary gas stove. It is also possible to get results from other heating methods such as a clear hard coal fire, but the trouble with such methods is that the article is very liable to get smoked. The colors obtained by the heat method come in this order if it is done slowly: First, orange red; Second, bluish purple; Third, brassy color; Fourth, dark red; Fifth, deep purple; Sixth, iridescent; Seventh, chestnut color. The first two colors partially come off when the lacquer or wax is applied. All the others are permanent if they are lacquered or waxed. The lacquer is applied as soon as the article is cold, the wax while it is still warm. Care must be taken when obtaining the chestnut color not to pass it into the flame any more when the chestnut color begins to come, because if the chestnut color is carried too far the color will flake off and the entire process of cleaning and coloring will have to be repeated.
No. 13. For a dead black finish on copper immerse in this solution: water, five quarts; one-fourth pound sulphate of potassium; two ounces of concentrated spirits of sal ammoniac.
No. 14. A steel gray dipping solution for copper is as follows: dissolve four ounces of muriate of arsenic in two quarts water. Use hot.