How to Create Black Light Halloween Messages With Your Kids

Do your kids like to send secret messages to their friends?

Want a cool way to explore science while playing in the dark?

Your family will be wowed by this fun and easy project that teaches the properties of fluorescent light.

In this article, I’ll show your budding scientists how to design their own secret messages and reveal them when the lights go out.

Black light Halloween science project: let kids design their own secret messages and reveal them when the lights go out.

Why Create Black Light Secret Images?

Black light secret images incorporate a whole lot of things that are awesome to kids (and maybe to you big kids, too!).

They appear to float in mid-air. They glow in the dark.

And not only do your kids get to create messages themselves, but they also control when the secret codes are revealed with a special, magical black light.

This is a fun and simple activity for a Halloween party, sleepover or anytime.

Use the image viewers as Halloween lanterns to add a spooky element to trick-or-treating and an extra way for you to see the kids in the dark. (Be sure to bring along a flashlight too.)

The keys to black light secret images are something you can find anywhere you can buy office supplies: highlighter markers. You may already have some in your home or office.

Highlighters are for more than just marking important text. They create bright, colorful pictures. Some highlighters are fluorescent and glow under a black light.

Be sure to use highlighters that contain fluorescent dye. You can use non-fluorescent pens, but the ink won’t glow in the dark and then you’ll have some disappointed kids on your hands.

To Make All of the Recipes, You Will Need

Preparation Time

10 to 15 minutes to build the viewer

Activity Time

Flash secret messages in the dark for as long as you’d like


Start on a flat surface like the kitchen table. After you’ve made your viewers, go into a room or area that’s safe when the lights go out

This activity combines a little art skill with science knowledge. Get ready to put on your artist’s beret and scientist’s safety glasses. Here’s a video that gives you an overview.

You’ll learn how to make glowing black light images like the ones in this video.

#1: Create Your Secret Images

Gather your materials and ask the kids to think of a message or image they’d like to see glowing in the dark.

secret message materials

Gather your secret code-making materials.

Use a pen to trace around the drinking end of the plastic cup on a white piece of paper. Don’t use thick paper—copy paper is perfect.

Use fluorescent highlighters to create designs and messages inside the circle.

fun activity

This activity is perfect for sleepovers, Halloween parties or just a night of glow-in-the-dark fun.

For your secret message to appear, the highlighter must contain fluorescent dye. The package will indicate if the highlighters are fluorescent.

Cut out the circle with scissors.

#2: Build a Black Light Viewer

Carefully poke a small hole in the middle of the bottom of the plastic cup using the sharp point of the scissors.

Apply a thin layer of glue around the cup edge.

glue paper to cup

Carefully glue the paper circle to the cup, making sure your design is facing out. You can also tape the paper to the cup.

Make sure the design is facing out of the cup. Glue (or tape) the paper circle to the cup opening.

Let the glue dry.

place mini black light

Squeeze the mini black light into the hole in the bottom of the cup.

Once the glue is dry, push the small bulb of the black light into the hole in the bottom of the cup.

#3: Floating Glow-in-the-Dark Pictures

Turn off the lights and turn on the black light.

Watch as your secret message appears. The highlighter ink glows in the ultraviolet light and your images seem to float in the dark.

dancing jack o lanterns

Spooky dancing jack-o-lanterns light up the dark and can also be used for trick-or-treating.

Share your artwork and messages with friends and family. To add extra fun, turn on some music and dance around with your glowing images.

How Does it Work?

To understand how this activity works, you have to learn about the two common types of glowfluorescence and phosphorescence.

Fluorescence is a type of glow that occurs when some form of radiation, like light, causes it to glow. Fluorescent things cannot glow without some form of energy. As soon as the light is removed, the glow stops. For example, glow-in-the-dark posters or papers will glow under a black light or even in the daylight, but cannot glow in the dark by themselves.

difference between lights

Use this project to demonstrate the difference between fluorescence and phosphorescence.

Phosphorescence is similar to fluorescence except that with phosphorescence, the glow continues after the light is removed. Glow-in-the-dark toys are charged or excited by white or ultraviolet light, then continue to glow even after the light source is removed.

For this secret message project to work, be sure to use fluorescent markers to draw your secret image.

Ask your kids to test their glow-in-the-dark images. Are they fluorescent or phosphorescent?

Some final thoughts

You’ll discover when you experiment with different colors that even though the fluorescent dye is in the ink, some colors will not glow in the ultraviolet light. Some colors may even look like they’ll glow when the lights go off.

colors glow brightly

Some colors glow more brightly than others.

Don’t get discouraged if some of the colors do not display exactly the way you want under the black light. Test the colors before gluing on your final designs.

different colors

Experiment with different highlighter colors and non-fluorescent pens.

Find creative ways to use the non-fluorescing with the fluorescing colors to create really incredible secret messages.

Looking for more glow-in-the-dark science experiments? Visit our experiment page for additional ideas.

What do you think? We want to see your glowing secret messages. Which colors worked and which ones didn’t? Share your designs and findings (with pictures) in the comments below.

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About the Author, Steve Spangler

Steve Spangler is an author, teacher, toy designer, Emmy award-winning television personality and creator of a huge soda mess. His appearances on television demonstrate his passion for making learning fun. Other posts by »


  1. Thanks, Steve! Can’t wait to make these for Halloween.

  2. Maria Teman Ward says:

    great idea, love it.

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