Home >>  Marking Cards Invisible Ink  >>  The Basics of Invisible Ink

The Basics of Invisible Ink

In April of this year, the CIA released its oldest classified documents and the last from the World War I era. Dating from 1917 and 1918, the papers mainly contain recipes for “secret writing”–instructions for agents of the Office of Naval Intelligence (the CIA did not yet exist) on how make invisible ink. Such a low-tech espionage method may seem quaint today, but invisible ink was once a very serious business and an important tool in a spy’s bag of tricks. So much so that the CIA bizarrely waited almost a century before revealing its most basic recipes to the public (information which was available on the web and to every Boy Scout), claiming even in the 90s that the material constituted a foundation upon which more modern tactics had been built and that invisible ink remained a viable tool for its agents.

While the use of invisible ink has now been almost entirely eclipsed by modern technology, its history is incredibly fascinating, and today as part of our Man Knowledge series we’ll explore its use through time.

There are two categories into which invisible inks fall: organic fluids and sympathetic inks. The former consists of the “natural” methods many of us tried our hand at as kids: lemon juice, vinegar, milk, sweat, saliva, onion juice, and even urine and diluted blood, to name a few. These organic invisible inks can be developed through heat, such as with fire, irons, or light bulbs, and some can be seen when placed under ultraviolet light. The organic fluids alter the fibers of the paper so that the secret writing has a lower burn temperature and turns brown faster than the surrounding paper when exposed to heat.

Sympathetic inks are more complicated chemical concoctions. Sympathetic inks contain one or more chemicals and require the application of a specific “reagent” to be developed, such as another chemical or a mixture of chemicals.

MESSAGE
*Name: E-mail:
*Phone / Whatsapp: Skype:
*Message:
Code: Refresh
LEAVE A MESSAGE
Name: Mark Charles IP: 207.161.51.20 Time: 2018-05-19 05:49:57
Content: Hi, I am looking for 3 pair of glasses and a pen/marker/ink that can be used to mark playing cards for an escape room puzzle. Glasses must be durable as they will be handled by hundreds of people. Shipping to Winnipeg, Canada
Admin_reply: Thanks for your inquiry about glasses, a pen/marker/ink for marking playing cards, I have sent you email, please check and reply, thanks
Name: Prakash IP: 192.119.160.242 Time: 2018-02-07 23:40:04
Content: I want uv contact lens but I want to know that how it works?
Admin_reply: Thanks for your inquiry about UV contact lenses, I have sent you email, please check and reply, thanks
Name: Filip IP: 95.170.234.75 Time: 2018-02-05 21:50:01
Content: Hi Are you selling some invisible pen or marker which will be compatible with uv contact lenses ??? Please contact me via email
Admin_reply: Thanks for your inquiry about invisible ink pen or marker for uv contact lenses, I have sent you email, please check and reply, thanks

First | Previous | | Last

×

E-mail: marked-cards2012@hotmail.com

Skype: marked-cards2012

WhatsApp / Wechat: +86 188 2517 5787