P PayBack Enlightened Joined Sep 13, 2004 Messages 554 Apr 30, 2008 #1 Ok in a packet of Cornflakes came a invisible ink spy type pen... with a blueish light on the other end to read the invisible ink. Would a blue LED work, or is this using a UV light? Surely not the latter on a toy?
Ok in a packet of Cornflakes came a invisible ink spy type pen... with a blueish light on the other end to read the invisible ink. Would a blue LED work, or is this using a UV light? Surely not the latter on a toy?
warlord Enlightened Joined Feb 22, 2008 Messages 362 Location Northern Illinois Apr 30, 2008 #2 blue led would work.
T Tempora Newly Enlightened Joined Mar 18, 2007 Messages 74 Location Greece,Thessaloniki May 2, 2008 #3 It could be a near UV spectrum, just below blue.
lctorana Flashlight Enthusiast Joined Jun 28, 2007 Messages 2,123 Location Melbourne, Australia May 2, 2008 #4 PayBack said: Ok in a packet of Cornflakes came a invisible ink spy type pen... with a blueish light on the other end to read the invisible ink. Would a blue LED work, or is this using a UV light? Surely not the latter on a toy? Click to expand... Just now tested my Cornflakes UV pen on my uranium-glass butter dish. And yes, I can confirm it really does emit UV light.
PayBack said: Ok in a packet of Cornflakes came a invisible ink spy type pen... with a blueish light on the other end to read the invisible ink. Would a blue LED work, or is this using a UV light? Surely not the latter on a toy? Click to expand... Just now tested my Cornflakes UV pen on my uranium-glass butter dish. And yes, I can confirm it really does emit UV light.
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