Dictionarium polygraphicum. Sympathetick Inks.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol II.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
Sympathetick Inks are such as can be made to appear and disappear very suddenly, by the application of something that seems to work by sympathy.

Take unflak'd lime two or three parts, and one of yellow orpiment; reduce them to powder, and mix them, adding to them fifteen or sixteen times as much water, as you have orpiment; pur them into a glass bottle or vial, and stop them with a cork and bladder, and set it in warm embers, shaking the vial now and then for five hours, and then warily decant the clear part, or rather filtrate it.

In the mean time, burn a piece of cork thoroughly; and when it is well inflamed, quench it in common water, or rather in brandy. It being thus redue'd to a friable coal, grind it in fair water, in which gum has been dissolv'd, and it will make a liquor as black as common ink.

While this is preparing, dissolve a quantity of red lead in three times as much distill'd or strong vinegar over warm embers, or of Saccharum saturni in three times the quantity of water for three or four hours, or 'till the liquor has a sweet taste. This liquor will be as clear as common water.

Having prepar'd the inks as before directed, write what you would write on paper with this last liquor, dry it, and nothing will appear.

Over the place write what you please with the second liquor, and it will appear as common ink. When it is dry, dip a piece of rag or spunge in the first liquor, rub it over the written place, and the black writing will vanish; and that wrote with the in visible ink will appear black and legible.

Again, take a book four or five inches thick, and on the first leaf write any thing with the last liquor; turn to the other end of the book, and rub there with a rag dipt in the first liquor, on that part, as near as you can guess, opposite to the writing; and leave also the rag there, clapping a paper over it. Then shutting the book nimbly, strike four or five smart strokes thereon with your hand, and turning the other side uppermost, clap it into a pres, or lay it under a good weight for a quarter of an hour, or half that time; then will the writing, done with the invisible be found legible.

2. Dissolve white or green vitriol in water, and writing with the solution, nothing will appear.

Boil galls in water, and dip a linnen rag in the decoction, and with it rub the place written before, and it will appear black and legible.

Rub it over again with spirit of vitriol, or its oil, and the writing will disappear again: rub it over again with oil of tartar per deliquium, and the letters will appear again, but of a yellow colour.