Secret Ink

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Secret Ink

 

a chemical compound in the form of a colorless or faintly colored liquid used to write secret messages. The juices of certain plants are sometimes used as secret inks. A text written with secret ink is invisible under normal conditions. In order to make the text visible, the document must be heated, exposed to ultraviolet radiation, or treated with chemical reagents.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
It produced 857 litres of secret ink added to the coloured material to seal meat at all the butchers in the country.
Secret ink: Tattoo's place in contemporary American culture.
While Al Qaeda mainly hid in the shadows of the Internet using it as a modern drop box or secret ink, Militants noisily using it to advertise itself, radicalise new recruits and intimidate with grotesque videos of beheadings, he said.
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Another memorandum dated June 14, 1918 - written in French - reveals the formula used for German secret ink, it added.
He couldn't build a radio mix secret ink or recruit a network.
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Police have been marking bottles of booze with secret ink in an effort to catch out under-age boozers.
Agents were armed with suitcase bombs, explosive clogs, secret ink and even incendiary cigarettes which created "a hot flame for five seconds" when lit.