This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
When the copper or coppered article is perfectly dry and the copper or copper coating made brilliant, which is produced by rubbing with a soft brush, put graphite over the piece to be bronzed so that the copper is simply dyed. Wipe off the raised portions with a damp cloth, so that the copper makes its appearance. Next put on a thin coat of Japanese varnish; wipe the relief again and let dry. Apply 1 or 2 coats after the first is perfectly dry. Handsome smoked hues may be obtained by holding the bronze either over the dust of lighted peat or powdered rosin thrown on lighted coal, so as to obtain a smoke which will change the color of the varnish employed. The varnish must be liquid enough to be worked easily, for this style of bronzing is only applicable to brass.
Abietate of silver, 1 part; essence of lavender, 1!) parts. Dissolve the abietate of silver in the essence of lavender. After the articles have been well pickled apply the abietate-of-silver solution with a brush; next place the objects in a stove and let the temperature attain about 150° C.
Blue bronze is produced by the wet process by coloring white bronze (silver composition) with aniline blue. A blue-bronze color can be produced in the ordinary way from white-bronze color, the product of pure English tin, and with an alum solution consisting of 20 parts of alum in 4,500 parts of water boiled for 5 hours and washed clean and dried. The bronze prepared in this manner is placed in a porcelain dish, mixed with a solution of 15 parts of aniline blue in 1,500 parts of alcohol, stirring the bronze powder and liquid until the alcohol has evaporated entirely and the bronze color becomes dry. This manipulation must be repeated 6 or 8 times, until the desired blue shade is reached. When the bronze is dark enough it is washed out in warm water, and before entirely dry 1 tablespoonful of petroleum is poured on 2 pounds of bronze, which is intimately mixed and spread out into a thin layer, exposed to the air, whereby the smell is caused to disappear in a few days.
To bronze wood, porcelain, glass, and metal by means of a water-glass solution, coat the article with potash water-glass of 30° Be. and sprinkle on the respective bronze powder.
Genuine bronze can be beautifully oxidized by painting it with a solution of 4 parts of sal ammoniac and 1 part of oxalium (oxalate of potash) in 200 parts of vinegar, allowing it to dry, and repeating the operation several times. These articles, protected against rain, soon lose the unpleasant glaring metallic luster and assume instead a soft brown tint, which bronze articles otherwise acquire only after several years' exposure to the atmosphere. A beautiful bronze color which will remain unaffected by heat can be imparted to bronze articles by the following process: The object is first washed in a solution of 1 part of crystallized verdigris and 2 parts of sal ammoniac in 260 parts of water, and then dried before an open fire till the green color begins to disappear. The operation is repeated 10 to 20 times, but with a solution of 1 part of verdigris crystals and 2 parts of sal ammoniac in 600 parts of water. The color of the article, olive green at first, gradually turns to brown, which will remain unaltered even when exposed to strong heat.