Writing in invisible ink can be an interesting experiment.
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?
Instructions
Creating the Ink
1. Laundry detergents with bluing agents are a good source for a fluorescent material.
Pour a small amount of the household bleach into a dish or measuring cup.
2. A cotton swab makes a good writing utensil.
Dip the cotton swab into the bleach and write a message on a sheet of paper.
3. When the writing dries, it will be invisible.
Let the bleach dry.
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. Use different cotton swabs for the other substances.
Using different cotton swabs, repeat the experiment using the laundry detergent (make it into a solution if it's a dry detergent), then the shampoo.
6. Artist's brushes can provide different textures.
Use the paint brush, toothpicks, and fountain pen to create different textures.
7. Look at these under the UV light in a darkened room.
Using Saliva for UV Ink
8. 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.
9. Let the saliva dry.
10. Shine the UV light on it in a dark room.
