A very nice trick. But i have no clue where i got this from though. Will post the link if i find it ! It is Wicked 😉
Get Instantly Arrested
No, don’t read this! You’ll be tempted to try it and end up in jail. Back in 1982 I was using some adhesive “window burglar alarm tape”, the metal stuff you burnish onto glass to detect breakage, and realized that it’s made of lead. With just this lead foil and a razor blade, I could make some lead-on-paper messages, put them in my carry-on luggage, and send a secret message which is visible only to the X-ray operator at the airport security station! Are those x-ray systems live-video or freeze-frame? Maybe I could even make a motorized animated sign, a little lead-foil creature who waves at the x-ray operator. And some modern x-ray units detect absorbtion spectra, displaying it in various colors, so materials such as silver-leaf from art supply stores will show up on their video display. Hey, rather than using lead foil, I could use lead oxide white pigment or “litharge”, the old fashioned lead paint. Make some silver chloride paint that shows up in color on the x-ray display. Use white paint on white paper and it would show up on x-ray, but to the eye be visible only as white paper. Print a litharge-ink silk-screen image of the x-ray photo of a human hand or head and stick it in your luggage. Will you be arrested for smuggling invisible body parts?