Boil pounded gallnuts, 40 parts, with water, 560 parts, until the whole amounts to 200 parts; filter, and add nitric acid, 2 parts, and a few drops of hydrochloric acid. Ferric chloride and antimonic chloride solutions may also be used to etch zinc.

Relief Etching of Zinc

The design is to be drawn with a solution of platinum chloride, 1 part, and rubber, 1 part, in water, 12 parts. The zinc plate is placed in dilute sulphuric acid (1 in 16). The black drawing will remain as it is.

Another compound for the drawing is made of blue vitriol, 2 parts; copper chloride, 3 parts; water, 64 parts; pure hydrochloric acid, l.1 specific weight. After the drawing is made, lay the plate in dilute nitric acid (1 in 8).

Etching Fluid for Aluminum

Dilute hydrochloric acid serves this purpose. Aluminum containing iron can be matted with soda lye, followed by treatment with nitric acid. The lye dissolves the aluminum, and the nitric acid dissolves the iron. Aluminum bronze is etched with nitric acid.

Etching Fluid for Tin or Pewter

Ferric chloride, or highly diluted nitric acid.

Etching Fluids for Silver

I

Dilute pure nitric acid.

II

Nitric acid (specific weight, 1.185), 172 parts; water, 320 parts; potassium bichromate, 30 parts.

Etching Fluid for Gold

Dilute aqua regia (=nitric and sulphuric acids, in the proportion of 1 in 3).

Etching Fluid for Copper, Zinc, and Steel

A mixture of 4 parts of acetic acid (30 per cent), and alcohol, 1 part; to this is added gradually, nitric acid, 1 part.

Etching Fluid for Lead, Antimony, and Britannia Metal

Dilute nitric acid.

Etching Powder for Metals (Tin, Silver, Iron, German Silver, Copper, and Zinc)

Blue vitriol, 1 part; ferric oxide, 4 parts. The powder, moistened, is applied to the places to be etched, as, for instance, knife blades. Calcined green vitriol can also be used.