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The History of Invisible Ink 41

As a kid I had a minor obsession with invisible ink after learning about it in a science club. An impressive stack of vinegar and lemon scented papers filled my desk, but the history of invisible ink is much more interesting than a summer enrichment program. Starting with the Roman general Pliny the Elder using milk from the thithymallus plant, to modern inks which are only visible under UV light, the science of invisible ink has grown quite complex. Some of the oldest CIA documents contain recipes for special inks, and MI6 and their very own "adult" mixture during WW1.
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The History of Invisible Ink

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  • by Anonymous Coward

    That's really his name?

    • That could be the last name of the next Bond girl, and then anyone who giggles can be told "Hey don't laugh, that's a real name!"

    • There's also a city/town near where I live called Cumming. Yea. The road signs say "Cumming, next exit".

  • Couldn't have asked for a better name...

    From the last link:

    Mansfield Cumming, ... was "making enquiries for invisible inks at the London University".

    In October he noted that he "heard from C that the best invisible ink is semen", which did not react to the main methods of detection. Furthermore it had the advantage of being readily available
  • Dried semen shows under two well known "development" methods, both heat and UV. Better to use "ink" that only show under uncommon reagent, but that user would be reasonably expected to possess for another use.
    • Better to use "ink" that only show under uncommon reagent, but that user would be reasonably expected to possess for another use.

      But any other "ink" wouldn't be nearly us fun to obtain, especially for the female agents.

      • The female agents also have a UV detected invisible ink source that responds to self-pleasure. Actually, the ink from that source may not be invisible for 3-7 days a month.
    • If they had the DNA technology they have today, it could also have functioned as a chemical signature for authentication: "Yep, we tested it, the message is from Agent XYZ alright".

      But then,I don't think I'd want my DNA in the hands of the enemy, should security be compromised.
      • You'd want to use something that functions as a hash of DNA. Some protein that's reasonably unique.
      • by arth1 ( 260657 )

        Wouldn't that be just half of the DNA?

        • You mean as in public key encryption? I wasn't thinking of anything that sophisticated. As is, it would have serious vulnerabilities, definitely: example- Bond sleeps with an enemy agent (who is maybe KGB, a double agent posing as a CIA agent), afterwards she excuses herself to the bathroom and scoops out his jizz (sorry, not the classiest description) seals it in an airtight vial and later forges a letter with it.
          Hmm.. if he had a threesome, it could bring a whole new meaning to "man in the middle atta
  • An old Roman version of invisible ink can be made in your own home. You need to collect your urine for several days and keep it uncovered in the sun so that it becomes more concentrated. keep it inside, like on your kitchen counter so it doesn't become contaminated with windblow stuff. after several days, it will become a dark amber color... this is what you want... for each gallon of urine, add two teaspoons of vinegar, one teaspoon of green food coloring (we're using a oxidized copper ion here), and

    • and finally.... to develop it... and remember, this only works on April 1st... is to use a concentrated Plutonium solution wiped over the surface with an organic cloth like cotton or rabbit skin

    • Informative, but honestly who is going to need a gallon of invisible ink? And I quail at the thought of "mix it all together with your hands and dip a straw into it and suck it up into the straw"

      Why can't we just make a very simple fountain style pen using a twig and pocket knife?

      • You missed the part where it was all an elaborate scheme to get you to suck up several-day-old urine in a straw.

        • You missed the part where it was all an elaborate scheme to get you to suck up several-day-old urine in a straw.

          BINGO! You win.

          I, however, fail, because I meant to submit it as Anonymous Coward... oh well....

      • Zing, successfully trolled :(
    • we're using a oxidized copper ion here

      I am dying to know where is here, where you find yourself in common need of peeing in a jar to make invisible ink.

  • Did every MI6 agent get a stack of porn to use when writing hidden messages?

  • Bet you cant

    read that!
  • Several substances were used, as documented in Led Zeppelins famous work "Led Zeppelin Traveling Riverside Blues":

    Squeeze my lemon 'til the juice runs down my leg Squeeze it so hard, I'll fall right out of bed Squeeze my lemon, 'til the juice runs down my leg Spoken: I wonder if you know what I'm talkin' about Oh, but the way that you squeeze it girl I swear I'm gonna fall right out of bed She's a good rider She's my kindhearted lady I'm gonna take my rider by my side I said her front teeth are lined wi

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