METHOD OF COLORING ALUM CRYSTALS.
In making these crystals the coloring should be added to the solution of alum in proportion to the shade which it is desired to produce. Coke, with a piece of lead attached to it in order to make it sink in the solution, is a good substance for a nucleus, if a cluster of crystals are to be formed. Any form, if wound around with knitting cotton, can be used, or the grasses above described can be dipped in these colored solutions, and very pretty results obtained.
Yellow: muriate of iron. Blue: solution of indigo in sulphuric acid. Pale blue: equal parts of alum and blue vitriol. Crimson: infusion of madder and cochineal. Black: Japan ink thickened with gum. Green: equal parts of alum and blue vitriol, with a few drops of sulphate of iron. Milk white: a crystal of alum held over a glass containing ammonia will become a milky white color upon its surface.
[Note.—To make an infusion of a substance you simply pour boiling water over it. The madder and cochineal are in the dry form, and only a little water should be used, as too much will make the color less brilliant.]
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