The Central Bureau of Investigation has released six of its World War 1 documents that reveal how certain ingredients could be used to create invisible ink.
“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 Washington Post quoted one of the documents dated from 1917 and 1918, as saying.
But there’s a warning for the intrepid spy: ‘Do not inhale fumes,’ it added.
While one document gives details about chemicals and techniques that can be used to create invisible ink called ‘secret writing,’ another one, from June 1918 and written in French, provides the formula the Germans apparently used for their invisible writing during World War I.
Announcing the release in a statement, CIA Director Leon Panetta said: “When historical information is no longer sensitive, we take seriously our responsibility to share it with the American people.”
In 1999, the agency had rejected a ‘Freedom of Information Act’ request to release the six documents, thinking that doing so “could be expected to damage the national security.”
However, a CIA spokeswoman said that they had now decided to release it because in recent years, “the chemistry of making secret ink and the lighting used to detect it has greatly improved,” and therefore it is not expected to cause any threat to national security.