A varnish for machinery and foundry patterns, which dries as soon as put on, gives the patterns a smooth surface, thus insuring an easy slip out of the mold, prevents the patterns from warping, shrinking or swelling, and is quite impervious to moisture, is prepared in the following manner: Thirty pounds of shellac, 10 pounds Manila copal, and 10 pounds of Zanzibar copal are placed in a vessel which is heated externally by steam, and stirred during 4 to 6 hours, after which 150 parts of the finest potato spirit are added, and the whole heated during four hours to 87 degrees C. This liquid is dyed by the addition of orange color, and can then be used for painting the patterns. When used for painting and glazing machinery it consists of 35 pounds of shellac, 5 pounds of Manila copal, 10 pounds Zanzibar copal and 150 pounds of spirit.
Thoroughly dissolve in a strong potash lye a quantity of finely pulverized gum sandarac. This solution is to be diluted with water, and then follows its precipitation with a copper salt solution, either acetate or sulphur. Wash and dry the green precipitation, which is then dissolved in oil of turpentine.
A green transparent varnish for metals is made by grinding a quantity of finely-powdered chromate of potash with one-half the quantity of Chinese blue, to which is added a sufficient amount of copal varnish, thinned with turpentine. If the alteration of the tone of the varnish is desired, the amount of the various ingredients used should be changed accordingly.
A good varnish for metals is made by decomposing potash or soda soap with sulphate of zinc. This soap is then purified by water, and after 10 per cent. of tallow has been added the mass is diluted by petroleum, which affects the dissolution of the metal soap. The compound is then filtered until it is bright and clear.
Dissolve 1 part white wax in 15 parts benzine, and apply a thin layer with a brush. This forms a perfect covering, and is easily removed when necessary.
Verdigris is made from either copper and vinegar, or by putting together sheets of copper with the skins of pressed grapes.
Wagner's Britannia metal is composed of:
83-100 parts Bismuth, 3 6-10 parts Zinc,
81 1-100 parts Copper, 9 66-100 parts Antimony,
85 64-100 parts Tin.
Warne's metal is composed of:
7 parts Nickel, 7 parts Bismuth, 3 parts Cobalt, 10 parts Tin.
This metal is white.
To wash brass with tin, boil together 6 pounds of cream of tartar, 4 gallons of water, and 8 gallons of grain tin or tin shavings, for half an hour in a porcelain-lined vessel; put clean brass ware in the boiling liquid for a few minutes, or until properly coated.
A compound for welding steel to steel is composed of:
10 parts Borax, 2 parts Sal-ammoniac, 1 part Flour of Sulphur.
Another for the same purpose is composed of 8 parts Calcined Soda,
15 5-10 parts Prussiate of Potash, 35 parts Common Salt,
41 5-10 parts Boric Acid,