Boom Splat Kablooey – Depth Charge

Steve Spangler teaches the science behind his messy antics.

You’ve seen the amazing reaction that occurs when Mentos and Diet Coke mix… but what else can you use to make a geyser and what’s the best way to get those geyser starters into your bottle of soda?  The Geyser Tube works great for a roll of Mentos, but for everything else you can imagine we’ve found something even better… the Geyser Tube Depth Charge.

Experiment Materials

  • Geyser Tube
  • Geyser starters, such as Skittles, rock salt, table salt, etc.
  • 2-liter bottle of soda
  • Depth Charge


  1. You’ll need a 2-liter bottle of diet soda (diet doesn’t make a sticky mess) and an outdoor location for your geyser. Select a flat surface on the lawn or driveway to place the bottle.
  2. Choose a geyser starter… remember you’re the scientist.  What do you think would make the best geyser?  Try anything from table salt to dog food. Use what you’ve learned in Mentos Geyser experiments to decide what to try. Remember that the reason Mentos work so well is because of the tiny (almost microscopic) pits and craters on the surface of the mint. Use the Depth Charge to test what you think will make the biggest geyser.
  3. Unwrap the string from your Geyser Tube and put the trigger pin into the hole at the base of the Geyser Tube.
  4. Unscrew the cap from the top of your Geyser Tube.
  5. Open the bottle of soda and attach the Geyser Tube.
  6. Load the Depth Charge with your geyser starter and carefully slide the loaded Depth Charge, open end up, into the Geyser Tube.  Screw the cap back on the Geyser Tube.
  7. Countdown… 3-2-1… and pull the string. The Depth Charge will fall to the bottom of the soda and instantly release your geyser starter! If you selected a good geyser starter, the soda will begin to erupt right away. How high did your soda fly?
  8. Pour the remaining soda out of the bottle and reclaim your empty Depth Charge. Rinse and dry the Geyser Tube and Depth Charge parts and you’re ready to try out your next experiment.

How Does It Work?

The Depth Charge was specially designed to allow you to test how well other materials work when it comes to creating a soda geyser. It’s tough to test how well table salt works if there’s not a good (and consistent) way to drop it into the soda. With the Depth Charge, it’s possible to really conduct tests under scientific conditions.

You probably noticed the small weight on the end of the Depth Charge. This causes it to drop quickly to the bottom of the soda bottle.  When the Depth Charge hits the bottom, the two sides split apart and release the material (whatever you picked for your geyser starter) into the soda.  It’s important to get the starter material to the bottom of the bottle as quickly as possible to get the greatest geyser effect. Also remember that the secret is to select a geyser starter that has a rough surface – a place for carbon dioxide bubbles to collect and finally escape. Filling the Depth Charge with smooth marbles will produce no geyser while tiny particles of sand or rock salt produce great geysers.

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