Well, Pilot went about it a different way. The packaging (and website) says this is a thermo-sensitive ink and that the heat generated by the "eraser" (actually a soft plastic or hard rubber nub that doesn't really rub off on the paper) is enough to make the ink disappear so that you can correct the mistakes you make.
My wife bought me one to play with because I like quirky pens. Don't ask. It writes just like a typical gel pen.
Sure enough, the hard "eraser" does work, and apparently quite well.
As you can see, all traces are gone. Holding it up to the light, this looks like a blank sheet out of my notebook. Holding it at an angle to the light, there are faint marks of the ink, but it's not legible. The marks could be passed off as impression from the page above it.
I decided to try an experiment with the temperature sensitive ink, and only seconds after being exposed to the cold air in my freezer, the ink started to reappear. It did get a little darker after a few minutes. I'm wondering if heat that didn't involve friction (a toaster oven, candle, clothes iron or steam) would result in a more legible message. Maybe I'll try that next.
There you have it. A completely innocuous method of passing messages that uses nothing suspicious whatsoever. Just a pen you bought at the drug store, and a burst of cold air to make it legible again.
There is always ultraviolet ink, lemon juice just about anything which discolors during a chemical reaction but does not damage the paper itself.
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Then there is always emptying the ink pens into an inkjet cartridge.
http://www.ehow.com/how_4464754_make-invisible-ink-printer-cartridges.html
True, there are lots and lots of ways to do invisible ink.
ReplyDeleteIn high school, my friends and I used to use cobalt chloride mixed with table salt, diluted in water, and refill old fountain pen cartridges. Getting the paper very, very dry (more than would usually be allowed given ambient humidity in a room) would reveal blue ink. You could do this with an electric hand dryer in the restroom or over a flame, similar to lemon juice. We'd usually further this with a tic-tac-toe symbol replacement code. That was more than ample "security" to keep the gestapo (ahem, teachers) guessing.
BUT... if you get stopped with lemon juice in a fountain pen or some other device that seemingly writes with transparent ink, you're immediately suspect. This carries a little more stealth and deniability (i.e. it is a real pen that writes with real permanent ink) while retaining many of the desirable characteristics of other so-called "invisible" inks. It also allows you to obscure your writings in seconds in a microwave or over some other heat source.
Oh, and I did test this out again this morning using the radiant heat off of a stove burner (holding the paper a few inches above the burner) to "erase" the ink. When placed in the freezer for a few seconds, it comes back almost to 100% clarity, unlike the friction erasure method used in the article.
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