Part 2 (1/2)

Put as much gold in as small a quant.i.ty of aqua regia as will dissolve it, and dilute it with two or three times the quant.i.ty of distilled water.

Next dissolve, in a separate vessel, fine pewter in aqua regia, and when it is well impregnated, add an equal quant.i.ty of distilled water.

Write your characters with the first solution: let it dry in the shade. To make them visible, draw a pencil or sponge, dipped in the second solution, over the paper, and the characters will appear of a purple colour.

_Invisible Silver Ink._

Dissolve fine silver in aqua fortis; and after the dissolution, add some distilled water in the same manner as in the gold ink.

What is written with the above ink will remain invisible for three or four months, if kept from the air; but may be easily read in an hour, if exposed to the fire, air, or sun.

_Invisible Yellow Ink._

Steep marigold flowers seven or eight days in clear distilled vinegar.

Press the flowers and strain the liquor, which is to be kept in a bottle well corked. If you would have it still more clear, add, when you use it, some pure water.

To make the characters visible, which you write with this ink, pa.s.s a sponge over the paper, dipped in the following solution:

Take a quant.i.ty of flowers of pansy, or the common violet, bruise them in a mortar with water, strain the liquor in a cloth, and keep it in a bottle.

_Invisible Red Ink._

To the pure spirit of vitriol or nitre, add eight times as much water.

Use the above solution of violets to make visible the characters written with this ink.

_Invisible Green Ink._

Dissolve salt of tartar, clean and dry, in a sufficient quant.i.ty of river water. Use the violet solution to render it visible.

_Another Invisible Green Ink._

Dissolve zaffre, in powder, in aqua regia, for twenty-four hours. Pour the liquor off, and the same quant.i.ty of common water, and keep it in a bottle well corked.

This ink will not be visible till exposed to the fire or the sun; and will again be invisible when it becomes cold.

_Invisible Violet Ink._

Express the juice of lemons, and keep it in a bottle well corked. Use the violet infusion to make the writing visible.

_Invisible Grey Ink._

Mix alum with lemon-juice. The letters written with this ink will be invisible till dipped in water.