To write on zinc first clean the surface of the zinc by rubbing with a sponge which has been plunged in dilute hydro-chloric acid and fine sand. Next dissolve 1 ounce and 4 drachms of sal-ammoniac and 1 ounce and 4 drachms of crystallized verdigris in a pint of warm water. Filter the solution after it has cooled and keep it in tightly corked bottles. After the zinc has been written on by this compound it should be allowed to remain in water for a few hours, and then dried and used without varnish. The writing should be (preferably) done with a quill. Should the zinc look greasy or should the writing run together the surface should be cleaned with a rag dipped in chalk.
To cut out iron plates with sulphuric acid, compound together 1 part of acid with 6 of water. Then coat the iron with wax, drawing the required design in same and placing the plate in this compound for several hours, which will cause the parts making the design to drop out. The same process is to be pursued for etching names, ornaments, letters, etc., upon sword-blades.
In order to cause the colors of the rainbow to appear upon gilded articles of brass, iron and other metals, as well as any other clean metal surface, make a bath by boiling for a half hour 14 1/2 drachms litharge and 3 1/2 ounces caustic soda with 1 quart of water. The object to be colored, which should have been first thoroughly pickled and cleaned, is to be connected with the wire of the positive pole of a bettery, while, as an anode, a platinum wire is used. If this wire is plunged in the bath without coming in contact with the article the layer at once is colored with a variety of colors, which take their origin from a more or less thick layer of the precipitated oxide of lead. If a piece of stout parchment paper is placed in a vertical position between the articles to be colored and the platinum wire, colors of all possible contrasts may be obtained. The parchment, however, should also be provided with radical segments, or numerous holes.
Isolit is the commercial name of a matrix mass for reproducing coins, medals, etc. It is composed of ozokerite in a pure state with the addition of 5 per cent. of sulphur and 7 per cent. of petroleum.
Black japan is made from Naples asphaltum, 50 pounds; dark gum-amime, 8 pounds, use, add linseed oil, 12 gallons; boil; add dark gum amber, 10 pounds, previously fused and boiled with linseed oil, 2 gallons; add the dryers. Used for wood or metal.
(2) Black japan is made: 1. Asphaltum, 3 ounces; boiled oil, 4 quarts; burnt amber, 8 ounces. Mix by heat, and when cooling thin with turpentine. 2. Amber, 12 ounces; asphaltum, 2 ounces; fuse by heat. Add boiled oil, 1/2 pint; resin, 2 ounces. When cooling add 10 ounces oil of turpentine. Both are used to varnish metals.
Black grounds for japans may be made by mixing ivory black with shellac varnish; or for coarse work, lampblack and the top coating of common seed lac varnish. A common black japan may be made by painting a piece of work with drying oil (oil mixed with lead) and putting the work into a stove, not too hot, but of such a degree, gradually raising the heat and keeping it up for a long time, so as not to burn the oil and make it blister. This process makes very fair japan and requires no polishing.