2535. Blue Sympathetic Inks

2535. Blue Sympathetic Inks. "Writing with copperas turns blue if wetted with a solution of prussiate of potassa.

Nitrate of cobalt turns blue on being wetted with a weak solution of oxalic acid.

Rice water or a solution of boiled starch turns blue in a solution of iodine in weak spirit.

2536. Brown Sympathetic Ink

2536. Brown Sympathetic Ink. A diluted solution of nitrate of silver turns brown by exposure to the sunlight.

2537. Yellow Sympathetic Ink

2537. Yellow Sympathetic Ink. Chloride of antimony, used as the ink, will become yellow by moistening with a decoction of galls.

2538. Green Sympathetic Ink

2538. Green Sympathetic Ink. Ar-seniate of copper, washed over with nitrate of copper, turns a beautiful green.

2539. Purple Sympathetic Ink

2539. Purple Sympathetic Ink. Purple is produced by using chloride of gold, and soaking in chloride of tin.

2540. Sympathetic Inks Developed by Heat

2540.    Sympathetic Inks Developed by Heat. There are a number of colorless substances that may be used as inks, which are developed by the application of heat only.

Sulphate of copper and sal ammoniac,mixed in equal parts, will become yellow if exposed to the fire.

Onion juice has the same property as the above mixture.

Lemon juice, a very weak solution of either aquafortis, oil of vitriol, common salt/or saltpetre, will turn yellow or brown on exposure to the fire.

A weak solution of chloride of cobalt and chloride of nickel is turned a beautiful green by heat.

A solution of chloride or nitro-muriate of cobalt, turns green when heated, and disappears again on cooling.

A dilute solution of chloride of copper becomes a fine yellow at a moderate heat, and disappears on cooling.

A solution of acetate of cobalt, with a little nitrate added to it, turns rose-colored by heat, and disappears again when cold.

These last, which disappear again on cooling, are the best sympathetic inks for purposes of correspondence, as the others are more or less indelible when once developed.

2541. Hoe's Composition for Printing Ink Boilers

2541.    Hoe's Composition for Printing Ink Boilers. This consists of glue and molasses, the proportions varying from 8 pounds of glue in summer to 4 pounds in winter, for each gallon of molasses. The glue should bo placed for 1/2 an hour in a bucket, covered with water, then pour the water off and allow the glue to soften. Put it into a kettle and heat it until thoroughly melted ; if too thick, a little water may be added. Lastly, the molasses is stirred in and well mixed with the glue. When properly prepared, an hour's boiling will be sufficient, as too much boiling is apt to candy the molasses. Pour into a clean mould well oiled with a swab.

2542. To Clean Ink Rollers

2542.    To Clean Ink Rollers. Rollers should not be washed immediately after use, as they will become dry and skinny, but they may be washed 1/2 hour before using again. In cleaning a new roller, a little oil rubbed over it will loosen the ink, and it should be scraped clean with the back of a knife; it should be cleaned this way for about a week, when lye may be used. New rollers are often spoiled by washing too soon with lye.