A recipe for sympathetic ink

— Amory, Thomas (1690/1-1788)

Place of Publication
Printed for J. Noon
1756, 1766
A recipe for sympathetic ink
Metaphor in Context
[10]It is of a solution of the ore of bismuth, we make that very curious and useful thing, called sympathetic ink, which is a liquor of a beautiful colour, like that of the lilach or pipe-tree blossom. The process in preparing this liquor is tedious and difficult by aqua fortis, aqua regis, and fire, and therefore the ink is rarely to be met with. It is not to be had, unless some gentleman who makes chemistry his employment, gives one a present of a bottle of it; as I do now to you, in hopes it may some time or other be of singular service to you; for I have conceived a great regard for you, tho' I never saw you before, as you seem not only more teachable than any I have met with, but to delight in the information I give you relating to chemical things.

Here I returned my Chemist many thanks, and professed my eternal obligation to him: that I could listen for years to him; and wished it was possible to become his disciple, that I might see him by experiment facilitate the study of a science, more entertaining, instructive, and extensively useful than any other. But how, dear Sir, am I to use this ink, you are so vastly good as to give me, [Page 346] to make it more useful than any other ink could be?

I will tell you (Ribble replied): you must write with this lilach-coloured liquor, on good well gummed paper, that does not sink; and the singularity of the ink, consists in its property of disappearing entirely, and becoming invisible, though it be not touched with any thing whatever: And this distinguishes it from all others. The writing must dry in a warm air, and while it is cold no colour can be perceived: but gently warming it before the fire, the writing gradually acquires a greenish blue colour, which is visible as long as the paper continues a little warm, and disappears entirely when it cools. When other sympathetic inks are made to appear by proper application, they do not disappear again; but this liquor from the ore of bismuth must have the fire or heat kept to it, to render it legible. If a man writes to his mistress, suppose, or to a minister of state, with lemon juice, once the writing has been warmed by the fire, and the letters by that means appear, the epistle may be afterwards read at any time and place; but if the lady's father should by accident get your letter, written in lilach-coloured liquor, it must still remain a secret to him: For if on getting it, and opening the seal, he could see no writing, and therefore imagining it was writ with lemon juice, or [Page 347] some other sympathetic ink, he should hold it himself to the fire, or bid his servant hold it to the heat, that the letters might be produced, and made visible, yet the moment bismuth-ink is taken away from the fire, and begins to cool, it is as invisible again, as a sheet of white paper. How serviceable this may be on various occasions, may be easily conceived.
(pp. 345-7
Searching in HDIS (Prose)
At least 4 entries in the ESTC (1756, 1763, 1766, 1770).

Text from first printing: The Life of John Buncle, Esq; Containing Various Observations and Reflections, Made in Several Parts of the World; and Many Extraordinary Relations, (London: Printed for J. Noon, 1756). <Link to ECCO><Link to LION>

See also The Life of John Buncle, Esq; Containing Various Observations and Reflections, Made in Several Parts of the World, and Many Extraordinary Relations, 2 vols. (London: Printed for J. Johnson and B. Davenport, 1766). <Link to Google Books>
Date of Entry

The Mind is a Metaphor is authored by Brad Pasanek, Assistant Professor of English, University of Virginia.