Spies, Invisible Ink, Toenails, and Other Declassified CIA Secrets

Secret messages written with invisible ink. It sounds like something straight out of a James Bond movie where the fate of the world rests upon the contents of the clandestine communication. It could also be something you attempted as a child, using lemon juice to write a confidential note to your best friend. Either way, the use of invisible ink seems like it belongs in the realm of fiction or make-believe and is not the sort of thing legitimate spymasters use in their trade.

If that’s what you believe, think again. In 2011, the Central Intelligence Agency (CIA) declassified several documents that reveal the techniques used by the world’s top spies during World War I. All of the documents can be viewed at in the site’s Freedom of Information Act Electronic Reading Room.

In the early years of the 20th century, the techniques were state of the art. From our 21st-century perspective, they sound like the sorts of things kids can do with a basic chemistry set.

Suppose, for example, that you’d like to sneak a peak at someone’s mail without getting caught. Editor’s Note: If you were born after 1997, or so, it might be helpful to know that people once communicated through a prehistoric medium called paper and ink. They deposited written documents in an envelope and sent them through a quaint courier system known as the postal service. The method described herein will not give you the sought-after results if you attempt to apply it to e-mail.

The method for opening an envelope is described in one declassified document: “Mix 5 drams copper acetol arsenate. 3 ounces acetone and add 1 pint amyl alcohol (fusil-oil). Heat in water bath — steam rising will dissolve the sealing material of its mucilage, wax or oil.”

The instructions also contain a warning: “Do not inhale fumes.”

An excerpt from a declassified document dealing with secret writing.

The previously-classified documents also provide helpful instructions about how to send secret messages. They include a recipe for invisible ink that was used by the Germans during World War I. The formula was discovered by France and shared with its Allies.

One document recommends that some of the invisible ink solutions be used with a quill pen rather than a steel pen because of the risk of corrosion. With instructions that we suspect continue to be included in the training for airport TSA agents, the documents advise “to suspect and examine every possible thing.” To that end, consider checking proven places where spies are known to hide secret messages, such as postage stamps, toenails, and medicine capsules.

Additional helpful suggestions for subterfuge included soaking a handkerchief, or any other starched substance, in nitrate, soda, and starch, to make a portable invisible ink solution. Putting the treated handkerchief in water would release a solution that could then be used to write secret messages.

The methods disclosed in these documents sound as if they could provide countless hours of entertainment for children of all ages. In the spirit of public service, Commonplace Fun Facts feels compelled to warn its younger readers that the documents described herein are now available to the public. Although you now have access to these espionage techniques, so does everyone else in your school. Keep that in mind before you pour out your heart in a confidential note to your secret love.

A special word of warning to middle school boys: although writing secret messages on toenails is an approved method of espionage, these documents reveal that dirt and charcoal dust can be used to make those messages visible. Think about that before flippantly disregarding your mom’s instructions to take a bath.

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