How to make UV pen ink

Written by steven crane
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How to make UV pen ink
UV pen ink is only visible under black lights. (fountain pen image by Pali A from

Everyone knows that secret undercover agents have gadgets to help them carry out their mission. Among their arsenal of gadgets and gizmos is the pen with invisible ink. Making this ink is surprisingly simple--something anyone can do at home in just a few steps. This ink will be invisible to the naked eye, but will glow brightly under a black light. Black lights emit ultraviolet light andpcauses certain chemicals in the club soda and washing powder, which are ingredients used in making homemade invisible ink, to fluoresce.

Skill level:

Things you need

  • Empty fountain pen (not a ballpoint pen)
  • Small jar
  • Club soda
  • Liquid washing powder
  • Black light

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  1. 1

    Open your bottle of club soda and pour it into your small jar. Leave the jar uncapped overnight to decarbonate the club soda.

  2. 2

    Add a few drops of washing powder to your decarbonated club soda. Cap the jar and gently invert the jar several times to mix in the washing powder.

  3. 3

    Take the jar into a dark room, such as a bathroom, and turn on your black light. Verify that the ink glows sufficiently. If the ink glows weakly, add a few more drops of washing powder.

  4. 4

    Fill your empty fountain pen with your new UV pen ink. You may now use your fountain pen to write invisible messages.

Tips and warnings

  • You can use tools other than fountain pens with your UV pen ink too; paint brushes work great for writing on walls or ceilings.
  • While adding washing powder to your club soda, be careful not to shake vigorously, as this will cause excess foaming and bubbles.

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