SPY Artifact: Handkerchief with Secret Writing

Invisible ink.  Lemon juice, milk, and, for those most desperate, urine are the most commonly known recipes for invisible ink.   These techniques were literally child’s play for many of us.  Yet, when Mata Hari was arrested with a vial of a German issued invisible ink, it was used as evidence of her status as a German spy.   But what use can these potions and methods practiced for centuries still hold for our national security?

Well, quite a bit according to the CIA.  The oldest classified documents in US archives happen to be German invisible ink recipes from 1917 and 1918. As recent as 2002, the CIA successfully defended the classification in federal court fearing the “risk of compromise of…intelligence methods” and of allowing the “more sophisticated methods of secret writing” to fall in terrorists hands.  Perhaps we have Mata Hari to thank for those recipes?

Although the CIA is still protecting the German’s secret recipes, we have our own rich tradition.  George Washington himself was an avid practitioner and dabbler in invisible inks.  Washington instructed the use of “sympathetic stain” developed by Jon Jay’s brother for the transmission of secret information.

In Invisible Ink by John Nagy, we are introduced to the American Revolution as this war of deception waged by British and American forces employing invisible inks, codes, secret rendezvouses, spy rings, and complicated military deception operations.  After their defeat England’s chief of intelligence was reputed to have said, “Washington did not really outfight the British, he simply outspied us!”  I guess tea makes a poor invisible ink…