Blacking Copper

To give a copper article a black covering, clean it with emery paper, heat gently in a Bunsen or a spirit flame, immerse for 10 seconds in solution of copper filings in dilute nitric acid, and heat again.

Red Coloring of Copper

A fine red color may be given to copper by gradually heating it in an air bath. Prolonged heating at a comparatively low temperature, or rapid heating at a high temperature, produces the same result. As

soon as the desired color is attained the metal should be rapidly cooled by quenching in water. The metal thus colored may be varnished.

To Dye Copper Parts Violet and Orange

Polished copper acquires an orange-like color leaning to gold, when dipped for a few seconds into a solution of crystallized copper acetate. A handsome violet is obtained by placing the metal for a few minutes in a solution of antimony chloride and rubbing it afterwards with a piece of wood covered with cotton. During this operation the copper must be heated to a degree bearable to the hand. A crystalline appearance is produced by boiling the article in copper sulphate.

Pickle for Copper

Take nitric acid, 100 parts; kitchen salt, 2 parts; calcined soot, 2 parts; or nitric acid, 10 parts; sulphuric acid, 10 parts; hydrochloric acid, 1 part. As these bleaching baths attack the copper quickly, the objects must be left in only for a few seconds, washing them afterwards in plenty of water, and drying in sawdust, bran, or spent tan.

Preparations of Copper Water

I

Water, 1,000 parts; oxalic acid, 30 parts; spirit of wine, 100 parts; essence of turpentine, 50 parts; fine tripoli, 100 parts.

II

Water, 1,000 parts; oxalic acid, 30 parts; alcohol, 50 parts; essence of turpentine, 40 parts; fine tripoli, 50 parts.

III

Sulphuric acid, 300 parts; sulphate of alumina, 80 parts; water, 520 parts.

Tempered Copper

Objects made of copper may be satisfactorily tempered by subjecting them to a certain degree of heat for a determined period of time and bestrewing them with powdered sulphur during the heating. While hot the objects are plunged into a bath of blue vitriol; after the bath they may be heated again.

COPPER ALLOYS

See Alloys.

COPPER CLEANING

See Cleaning Preparations and Methods.

COPPER ETCHING

See Etching.

COPPER IN FOOD

See Pood.

COPPER LACQUERS

See Lacquers.

COPPER PAPER

See Paper, Metallic.

COPPER PATINIZING AND PLATING

See Plating.

COPPER POLISHES

See Polishes.

SEPARATION OF GOLD FROM COPPER

See Gold.

COPPER SOLDER

See Solders.

COPPER VARNISHES

See Varnishes.