invisible ink

American  

[in-viz-uh-buhl ingk] / ɪnˈvɪz ə bəl ˈɪŋk /

noun

1. a fluid for producing writing that is invisible until brought out by heat, chemicals, etc.

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invisible ink British  

noun

1. a liquid used for writing that does not become visible until it has been treated with chemicals, heat, ultraviolet light, etc

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Etymology

Origin of invisible ink

First recorded in 1675–85

Example Sentences

In another, attributed to Aeneas the Tactician, a message hides dots of invisible ink over certain letters, which spell out the true message.

From Scientific American • Jun. 15, 2023

Whether she's aware of the passages written in invisible ink in the margins and paragraph breaks is not for me to know or decode for my entertainment.

From Salon • Feb. 26, 2023

“But a close look at their skeletons and the similarities with pterosaurs became apparent, like invisible ink being held to the light.”

From New York Times • Oct. 5, 2022

He explained the invisible ink as a “toy purchased many years ago for entertainment,” and the other items to also be innocuous.

From Seattle Times • Aug. 22, 2022

When caretakers doled out the food, they trimmed a boy’s ration card and pressed his finger in invisible ink.

From "Lost Boy, Lost Girl" by John Bul Dau