sympathetic ink

American  

[sim-puh-thet-ik ingk] / ˌsɪm pəˈθɛt ɪk ˈɪŋk /

noun

1. invisible ink.

---

sympathetic ink British  

noun

1. another term for invisible ink

---

Etymology

Origin of sympathetic ink

First recorded in 1715–25

Example Sentences

Thomas Hardy, most Martian-eyed of diarists, wrote one freezing January that "Cold weather brings out upon the faces of people the written marks of their habits, vices, passions, and memories, as warmth brings out on paper a writing in sympathetic ink."

From The Guardian

Another sympathetic ink is afforded by chloride of gold, which becomes of a reddish purple when acted upon by a salt of tin.

From Project Gutenberg

A red sympathetic ink may be made in the following manner: Write with a very dilute solution of perchloride of iron—so dilute, indeed, that the writing will be invisible when dry.

From Project Gutenberg

Cobalt, dissolved in aqua regia, makes an excellent sympathetic ink, appearing green when held to the fire, and disappearing when cold, unless it has been heated too much, when it burns the paper.

From Project Gutenberg

By way of variation the chosen word may be produced with the sympathetic ink, or it may be revealed by the method employed in "A New Postal Trick."

From Project Gutenberg