George Washington received a letter from John Jay, written November 19, 1778, “This will be delivered by my Brother, who will communicate & explain to your Excellency a mode of Correspondence, which may be of use, provided proper agents can be obtained.”
“I have experienced its Efficacy by a three Years Trial. We shall remain absolutely silent on the Subject. I have the Honor to be with the highest Esteem & Respect Your Excellencys most obedient Servant. John Jay”
John Jay was a Founder, delegate from New York to the First and Second Continental Congress (and served as President of the assembly from December 10, 1778 to September 28, 1779), served as the second Secretary of Foreign Affairs until the office was changed to ‘Secretary of State,’ wrote several of the Federalist Papers, signer of the Treaty of Paris, Second Governor of New York and First Chief Justice of the United States.
James Jay, the brother of John Jay (referred to in John Jay’s letter above), was a physician practicing in England at the time, created a chemical solution out of tannic acid to be used as an invisible ink, and supplied quantities of the stain to the colonists.
George Washington himself instructed his agents in the use of what was referred to as the ‘sympathetic stain,’ noting that the ink “will not only render … communications less exposed to detection, but relieve the fears of such persons as may be entrusted in its conveyance.”
Washington suggested that reports could be written in the invisible ink “on the blank leaves of a pamphlet … a common pocket book, or on the blank leaves at each end of registers, almanacks, or any publication or book of small value.”
James Jay studied and practiced medicine in Great Britain from the 1750s until the outbreak of the Revolutionary War. He developed his invisible ink in 1775 and used it throughout the war in correspondence with his brother. He never disclosed the recipe, and although he exported small quantities to America for use in the Culper spy ring, it always remained in short supply.
A correspondent would write a letter using the ink on white paper, and the recipient would apply a reagent in order to read it. George Washington used the code word “medicine” to refer to the ‘sympathetic stain’ in his future correspondence with James Jay.
Espionage was an important part of the American Revolution; George Washington sought spies and suggested various forms of communication, including the use of invisible ink in correspondence relating such.
Acquiring intelligence about troop movements, supplies, and battle plans was General Washington’s highest priority. Because such field reports could not be overtly communicated to him, placing his agents at great risk, Washington used an 18th-century form of invisible ink known as “sympathetic stain.” (History Channel) (Mount Vernon)
Spying and Forms of Communicating
Ciphers and secret codes were used to ensure that the contents of a letter could not be understood if correspondence was captured. In ciphers, letters were used to represent and replace other letters to mask the true message of the missive.
The letter’s recipient utilized a key – which referenced corresponding pages and letters from a well-known book, such as Entick’s Dictionary – to decode the document’s true message. Some spy groups even created their own pocket guide to serve as a cipher’s key.
Similarly, some letters were written in intricate secret codes where numbers and special characters replaced letters.
One form of secret writing used by both the British and American armies was invisible ink. During the Revolutionary War invisible ink usually consisted of a mixture of ferrous sulfate and water.
The true contents of letters were also hidden through the use of mask letters. These documents were intended to be viewed by a recipient who would place a shaped template over the full letter. The true message of the letter would then appear within the boundaries of the “mask.” The letter and the “mask” were usually delivered by separate couriers to ensure that the trick would go undetected.
British spies placed rolled up letters and small notes into a variety of holsters to hide potentially sensitive information. The hollowed out quills of large feathers that were used as writing utensils, for example, could hide a tightly rolled up letter.
Other materials were used to hide messages, ranging from buttons on a textile to hollowed out small, silver balls.
One particularly unlucky British spy named Daniel Taylor was caught in New Windsor, New York with a message sent from Henry Clinton to John Burgoyne hidden inside one of these small silver balls.
In haste, the spy swallowed the silver ball to avoid detection. However, Patriot soldiers forced the spy to drink a purgative and vomit up the ball. Momentarily undeterred, Taylor grabbed the ball and swallowed it again. Under the threat of being hanged and having the ball cut out of his stomach, Taylor relented. However, Taylor would eventually meet the cruel fate of the gallows, executed on October 16, 1777.
Black Chamber Operations
The Americans operated Black Chambers (secret offices where sensitive letters were opened and deciphered by public officials) in the Highlands and General Philip Schuyler ran one in upstate New York.
The stamp in the seal would be duplicated, the letter was opened and if needed transcribed, and the letter resealed using the duplicate seal. The French started a Black Chamber operation in 1590. The British operated a black Chamber in the British post office since at least 1732 and since 1765 all diplomatic mail was read.
Washington had set up both New York Black chambers, the one in the highlands and General Schuyler’s operation.
Click the following link to a general summary about Invisible Ink:
