3384. To Color Brass Grey-Green

3384.     To Color Brass Grey-Green. Dipped into a bath of copper, the brass being first polished, as in last receipt, the resulting tint is a grayish green.

3385. To Color Brass Violet

3385.     To Color Brass Violet. A beautiful violet is obtained by immersing the polished brass for a single instant in a solution of chloride of antimony, and rubbing it with a stick covered with cotton. The temperature of the brass at the time the operation is in progress has a great influence upon the beauty and delicacy of the tint; in this instance it should be heated to a degree so as just to be tolerable to the touch.

3386. To Give Brass a Moire Appearance

3386.      To Give Brass a Moire Appearance. A moire appearance, vastly superior to that usually seen, is produced by boiling the object in a solution of sulphate of copper. According to the proportions observed between the zinc and the copper in the composition of the brass, so will the tints obtained vary. In many instances it requires the employment of a slight degree of friction, with a resinous or waxy varnish, to bring out the wavy appearance characteristic of moiré, which is also singularly enhanced by dropping a few iron nails into the bath.

3387. Black Lacquer for Brass

3387. Black Lacquer for Brass. There are two methods of procuring a black lacquer upon the surface of brass. The one usually employed for optical and scientific instruments consists in first polishing the object with Tripoli, then washing it with a mixture composed of 1 part nitrate of tin and 2 parts chloride of gold, and, after allowing this wash to remain for nearly a quarter of an hour, wiping it off with a linen cloth. An excess of acid increases the intensity of the tint.

By another method copper turnings are dissolved in nitric acid until the acid is saturated; the objects are cleaned, immersed in the solution, and subsequently heated moderately over a charcoal fire. This process must be repeated in order to produce a black color, as the first trial only gives a deep green, and the finishing touch is to polish with olive oil.

3388. To Give Brass an English Look

3388. To Give Brass an English Look. Much pains are taken to give brass objects an English look. For this purpose they are first heated to redness, and then dipped in a weak solution of sulphuric acid. Afterwards they are immersed in dilute nitric acid, thoroughly washed in water, and dried in sawdust. To effect a uniformity in the color they are plunged into a bath consisting of 2 parts nitric acid and 1 part rain water, where they are suffered to remain for several minutes. Should the color not be free from spots and patches, the operation must be repeated until the desired effect is produced.

3389. To Clean Brass

3389.    To Clean Brass. Brass and copper are best cleaned with sweet oil and Tripoli, powdered bath-brick, rotten stone, or red brick-dust, rubbed on with flannel and polished with leather. Vitriol and muriatic acid make brass and copper very bright, but they very soon tarnish, and consequently require more frequent cleaning. A strong lye of roche-aluin and water will also improve brass. A solution of oxalic acid rubbed over tarnished brass with a cotton rag, soon removes the tarnish, rendering the metal bright. The acid must be washed off with water, and the brass rubbed with whitening in powder and soft leather. When acids are employed for removing the oxide from brass, the metal must be thoroughly washed afterwards, or it will tarnish in a few minutes after being exposed to the air.