DIY: Retrofit an Inkjet Printer with Invisible Ink

While I doubt the super serious stiff in this DIY video is actually a super spy, he does have the DIY know-how necessary to hack apart an inkjet printer and make it into an invisible ink-spitting espionage machine. Enjoy! [MAKE]


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I've read that real spies often use bodily fluids such as semen as invisible ink. You could probably use that instead of lemon juice. Then the message would show up under ultraviolet light. And if you had to eat the message in an emergency, it wouldn't be so sour...