How to Make Invisible Ink for UV Lights

Written by carolyn kaberline
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How to Make Invisible Ink for UV Lights
Writing in invisible ink can be an interesting experiment. (writing image by Horticulture from

Almost everyone at some time in her childhood has delighted in finding a way to communicate in a secret language--thus Pig Latin is reinvented yet again, and new alphabet-number codes arrive that only a best friend knows. And what youngster has not tried to write in invisible ink at some point? The simplest way to create invisible ink, of course, is simply to write with lemon juice and let it dry; exposing the dry lettering to heat will make the writing legible once again. But what about a way to make ink that's visible to ultraviolet light instead of heat?

Skill level:

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Things you need

  • Washing powder with a bluing agent
  • Household bleach
  • Shampoo for grey or white hair
  • Cotton swabs
  • Paint brush (used for models)
  • Toothpicks
  • Portable black light

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    Creating the Ink

  1. 1

    Pour a small amount of the household bleach into a dish or measuring cup.

    How to Make Invisible Ink for UV Lights
    Laundry detergents with bluing agents are a good source for a fluorescent material. (Cleaning materials image by TekinT from
  2. 2

    Dip the cotton swab into the bleach and write a message on a sheet of paper.

    How to Make Invisible Ink for UV Lights
    A cotton swab makes a good writing utensil. (cotton swab image by timur1970 from
  3. 3

    Let the bleach dry.

    How to Make Invisible Ink for UV Lights
    When the writing dries, it will be invisible. (chained pieces of paper image by Olga Sapegina from
  4. 4

    Shine the black light on the paper in a darkened room. Your message should appear each time the UV light shines on it.

  5. 5

    Using different cotton swabs, repeat the experiment using the washing powder (make it into a solution if it's a dry detergent), then the shampoo.

    How to Make Invisible Ink for UV Lights
    Use different cotton swabs for the other substances. (cotton swabs image by timur1970 from
  6. 6

    Use the paint brush, toothpicks, and fountain pen to create different textures.

    How to Make Invisible Ink for UV Lights
    Artist's brushes can provide different textures. (artist"s brushes image by MAXFX from
  7. 7

    Look at these under the UV light in a darkened room.

    Using Saliva for UV Ink

  1. 1

    Place some saliva on your finger and trace a design on a piece of paper with it. Since many body fluids, including saliva and urine, are somewhat fluorescent, crime scene investigators often scan a darkened area with UV light to search for this type of evidence.

  2. 2

    Let the saliva dry.

  3. 3

    Shine the UV light on it in a dark room.

Tips and warnings

  • If you'd like larger supply of ink, you might want to try filling a clean bingo or shoe polish dauber. This is especially good for art projects.

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