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Bronzing with Black-Lead

to remain on for about 12 or 15 minutes, After the medal has been well cleaned from wiping it off with a linen cloth. An excess wax or grease, by washing it in a little of acid increases the intensity of the tint. In caustic alkali, brush some black-lead over the other method, copper turnings are dismethod, copper turnings are disthe face of it, and then heat it in the same solved in nitric acid until the acid is saturaacid until the acid is saturaway as described in No. 3773 for crocus; or a ted the objects are immersed in the solution, thin paste of black-lead may be used, and the cleaned, and subsequently heated moderately processes already referred to be repeated until over a charcoal fire. This process must be the desired brown tint is obtained. In this repeated in order to produce a black color, as kind of bronze a little hematitic iron ore, the first trial only gives a deep green; when which has an unctuous feel, may be brushed the desired color is attained, the finishing over the face of the bronze, by which a touch is given by polishing with olive oil. beautiful lustre is imparted to it, and a con- 3780. Black Bronzes. Many metallic siderable variety in the shade may be obtained. In the brown bronzes the copper is slightly oxidized on the surface. solutions, such as weak acid solutions of platinum, gold, palladium, antimony, etc., will impart a dark color to the surface of medals when they are dipped into them. The medal, after being dipped into the metallic solution, is to be well washed and brushed. In such bronzes the metals contained in the solution are precipitated upon the face of the copper medal, which effect is accompanied