Welcome to Steve Spangler Science. Skip directly to: main content, navigation, search box.

Glowing Tonic Geyser Add a little black light and tonic water glows a cool blue!
print this page

Glowing Tonic Geyser
Glowing Tonic Geyser
Glowing Tonic Geyser
Glowing Tonic Geyser Glowing Tonic Geyser

Tonic water might not be your first choice for a beverage, but it's the secret ingredient you'll need to make a glowing geyser. It turns out that tonic water will glow under a black light because tonic water contains quinine, a chemical that was originally added to tonic water to help fight off malaria in places like India and Africa. While the tonic water we drink today only contains a small amount of quinine, it's still enough to make your drink glow under black light. Combine this with Steve Spangler's joy of shooting off soda geysers, and you have yourself a very cool Halloween party idea.

Materials

  • Portable ultraviolet light
  • Bottle of tonic water (unopened)
  • Drinking glass, clear
  • Darkened room

If you want to do Steve's Mentos Glowing Geyser demo, you'll need a roll of Mentos, a 2-liter bottle of tonic water and a Geyser Tube (or another creative way to drop the Mentos into the soda).
  1. Open the tonic water and pour some into a large, clear drinking glass.
  2. Place a white sheet or poster board behind the glass to create a white background.
  3. Turn off all the lights and completely darken the room. Turn on the black light and shine it on the tonic water. Hey, what happened? The water is glowing blue!

Glowing Tonic Geyser

The following explanation uses the Geyser Tube as a triggering device for the glowing geyser.

  1. You’ll need a 2-liter bottle of tonic water and an outdoor lo
    cation for your geyser.
  2. Start by tying one end of the string to the trigger pin (the string might already be attached to the pin).
  3. Open the bottle of soda and attach the Geyser Tube. Put the trigger pin into the hole at the base of the Geyser Tube.
  4. Twist off the top cap on the Geyser Tube and drop 7 MENTOS candies into the tube. The trigger pin will keep the candy from falling into the soda… before you’re ready. Replace the twist-on cap.
  5. Warn everyone to stand back and turn on your black light. Countdown… 3-2-1… and pull the trigger. The MENTOS will drop and the tonic water will go flying into the air!
Remember that electricity and flying soda do not mix! It's best to use a battery powered black light instead of anything that requires regular electricity from the wall.

How does it work?

The black light gives off UV light which is a higher energy light than visible light and the human eye is not able to see it well. So, if ultraviolet light is virtually invisible, how can the tonic water glow so brightly? The tonic water's color under the UV black light is fluorescent-blue because it contains quinine, a substance that changes when it absorbs UV light. When the black light shines on the tonic water, the tonic water absorbs the light and excites the electrons. Since the electrons naturally want to return to their original relaxed state (who wouldn’t?), they give off energy that has a wavelength in the blue part of the visible spectrum. That’s why the tonic water has an eerie blue glow in the presence of ultraviolet light!

If you're curious about the MENTOS reaction, visit the MENTOS Geyser experiment page.

Best Sellers