The CIA declassified six documents from World War I, dated 1917. The contents are interesting, painting an image of an era of secrecy before the advent of computers and encryption.

The documents are the formulas used by the Germans to create “secret ink.” In other words, they’re invisibility ink recipes — some more complex than others.

Thefirst andsecond reports contain untranslated measurements and ingredients.

Thethird document on “Secret Writing” outlines a trick to use chemicals to render writing invisible. It includes five recipes, one using lemon juice, another with rice starch, and three requiring specialized chemicals.

Given the contents of document three, it looks like the recipe could was used on shirts, particularly under their collars, rather than being written on paper that would be more obvious.

Thefourth document looks like a 12 step procedure to decode documents. Included are steps to “run a warm iron over the surface” or “dry in the air,” and it goes on to describe which chemicals each process will reveal.

Thefifth andsixth documents look like cover sheets and ingredient lists, in English this time.

Photo Credit:”Down in a Shell crater, We Fought Like Kilkenny Cats” – Battle of Cambrai -Copyrighted, Underwood & Underwood. USA copyright expired.

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Joshua Philipp is the founder and editor of He's also an award-winning journalist at Epoch Times.

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