GEEK TOY OF THE WEEK: INVISIBLE INK PEN
by hazed
Calling all budding spies. Here's just what you need to keep your messages secret. It's a pen that writes with ink which changes from visible to invisible very easily - it's temperature sensitive. Write at room temperature and it's visible; heat it with a hairdryer and it vanishes, and it won't reappear unless you put it in the freezer. You can switch it between visible and invisible as often as you want. Amazing!
The pen costs $28. Read about it here.
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