It is comparatively easy to get a nice antique finish on copper or copper-plated articles, but the treatment of brass is more difficult. Most of the processes used do not give a nice, clear black, but instead, a dull or grayish black coating. At one time, when visiting the shop of the Puritan Mfg Co., Decatur, Ill., I noted the beautiful jet black of the brass articles made up with the antique finish, and upon expressing my curiosity as to how it was obtained, was offered the formula. The articles are first dipped into a strong, hot solution of potash. and then well rinsed in water; they are then immersed in a mixture of one part sulphuric and two parts nitric acid, and instantly rinsed in clear, cold water. Next they are placed in a bath consisting of two ounces acetate of lead and one ounce hyposulphite of soda to each gallon of water in the tank. This solution must be almost boiling when used. The brass is moved around in this until the desired black is obtained, then rinsed and dried. When dry and cool spot on a rag wheel. If brass doesn't turn black enough in above solution add just a little more lead. Ethan Viall.
I have found that the following process makes a very good lacquer for the brass parts of fine instruments, and that it requires but little labor to prepare. Make four alcoholic solutions in separate bottles of each of the following gums: Unbleached shellac, dragon's blood, annatto, and gamboge, in the proportions of about one ounce of the gum to a pint of alcohol. Keep these solutions about a week in a warm place, on a hot water or steam radiator, for instance, shaking the bottles frequently. It will be found that the alcohol will not dissolve all of the gum, but that within half an hour after shaking, a precipitate will settle on the bottom of the bottle, leaving a perfectly transparent but highly colored liquid above, which deepens in color from day to day. Decant this off, and filter through cloth, placing the liquids in tightly corked bottles. A word of caution should be given in the case of shellac. Most readers of Machinery are familiar with the yellow opaque shellac varnish of the pattern-maker. This is useless. But if the above proportions are used, and the solution kept warm, say 130 to 180 degrees F., a light flocculent precipitate will settle out, leaving a transparent wine-colored liquid above. It is this liquid which must he used. The four solutions should now be mixed. Equal parts of each give a rich golden yellow. After mixing, the solutions should be boiled down to about one-third of the volume, great care being used not to ignite the alcohol. Heat a piece of cast iron over a Bunsen burner, and as soon as this is hot, turn out the burner and place the solution on the iron and allow it to boil. When it ceases to boil, repeat the Process. When cold this solution may be applied with a brush to the brass in the usual way, the brass having been polished with jewelers' fine emery paper, and slightly warmed. Though slightly harder to apply than the commercial lacquers, it possesses none of the disagreeable odor of the banana oil which they contain. H. C. Lord.