Make Invisible Ink for Black Fluorescent Lights
Invisible inks have been used for some time in espionage, anticounterfeiting and security roles. Several distinct types of invisible inks exist, but some are visible under a black (also called UV, or ultraviolet) light. Within this type, some inks will either reflect UV light and fluoresce under a black light while others will absorb the UV light and not fluoresce; these latter inks will appear darker when presented on fluorescent paper under UV light.
- Detergent
- Petroleum jelly
- Fine paintbrush
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Instructions
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1
Mix a small quantity of detergent with water until the consistency is just thicker than water. Petroleum jelly is effectively a ready-made black-light invisible ink.
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2
Apply a small quantity of your invisible ink to your writing surface of choice using a fine paintbrush. Try writing a "secret" message. Note that at this stage, unless your black light is already on, the message will still be invisible.
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3
Turn on your black light and place your writing underneath the light. Your message is now visible.