Prep. 1. A mixture of nut-galls, 4 parts, and calcined sulphate of iron, 1 part (both perfectly dry and reduced to very fine powder), is rubbed over the surface of the paper, and is then forced into its pores by powerful pressure, after which the loose portion is brushed off. Writes black with a pen dipped in water.
2. From persulphate of iron and ferrocyanide of potassium, as the last. Writes blue with water.
3. As the last, but using sulphate of copper instead of sulphate of iron. Writes reddish brown with water.
4. The paper is wetted with a colourless solution of ferrocyanide of potassium, and after being dried is written on with a colourless solution of persulphate of iron. Writes blue.
Obs. The above applications, we need scarcely say, are more amusing than useful. See Sympathetic ink.
Paper, Incombus′tible. See Incombustible fabrics.
Paper, Irides′cent. Prep. (Beasley.) Sal ammoniac and sulphate of indigo, of each 1 part; sulphate of iron, 5 parts; nut-galls, 8 parts; gum Arabic, 1⁄8th part; boil them in water, and expose the paper washed with the liquid to (the fumes of) ammonia.
Paper, Issue. Syn. Charta ad fonticulos, L. Prep. (Soubeiran.) Elemi, spermaceti, and Venice turpentine, of each 1 part; white wax, 2 parts; melt them together by a gentle heat, and spread the mixture on paper. Used to keep issues open.
Paper, Lithograph′ic. Prep. 1. Starch, 6 oz.; gum Arabic, 2 oz.; alum, 1 oz.; make a strong solution of each separately, in hot water, mix, strain through gauze, and apply it whilst still warm to one side of leaves of paper, with a clean painting-brush or sponge; a second and a third coat must be given as the preceding one becomes dry; the paper must be, lastly, pressed, to make it smooth.
2. Give the paper 3 coats of thin size, 1 coat of good white starch, and 1 coat of a solution of gamboge in water; the whole to be applied cold, with a sponge, and each coat to be allowed to dry before the other is applied. The solutions should be freshly made.