To recap:

  • In Episode 1, we discussed how to make a soda geyser generator
  • In Episode 2, we discussed carbonation, the “fuel” for a soda geyser
  • In Episode 3, we discussed nucleation, the “trigger” for a soda geyser

Now it is time to explore how to make the best possible soda geyser. So, we’ll start with what brand of soda works best. It turns out that different brands of soda have different solubility of carbon dioxide. That means that different sodas can dissolve different amounts of carbon dioxide; the greater the solubility, the more carbon dioxide is dissovled, so more “fuel” for the geyser. 

According to one study, Diet Coke has the greatest solubility of carbon dioxide. But we’re not going to take their word for that. After all, if we did that, we wouldn’t have an excuse to set off all the soda geysers. You can test it, too!

The key is to do a controlled experiment. That means we only change one variable (one thing that could affect the experiment) and try to control, or keep constant, the other variables as much as possible. The variable you change is called the “experimental variable” and the ones you try to keep constant are “controlled variables.” So, be sure to store all your sodas in the same place until you are ready to launch them and use the same number of Mentos for each experiment. There may be some factors that can’t be controlled without taking more extreme measures (ex. wind – for some reason they wouldn’t let me set them off inside the Children’s Museum of Houston!), but do the best you can. Finally, repeat your tests several times and take the average of your data (we did three for each brand of soda).

What to Do:

  1. Buy or build a soda geyser generator (building one is covered in episode 1).
  2. Buy lots of Mentos (typically there are 14 in a roll and we used 7 per each launch) and several brands of soda (several of each brand).
  3. Get 2 partners – one will launch the geyser and the others can measure the height.
  4. Select a brand of soda.
  5. Set up the soda geyser generator per instructions.
  6. Countdown and release the geyser.
  7. Measure the maximum height of the geyser and record. We used some homemade altitude trackers like the ones here. We’ll go over this in a future O Wow Moment video.
  8. Calculate the average height of all your launches.
  9. Repeat steps 5-8 several times for each brand of soda (we did three tests per brand). MAKE SURE TO THOROUGHLY DRY OUT YOUR GEYSER GENERATOR BETWEEN LAUNCHES.
  10. Repeat steps 4-9 for each brand of soda. Compare the averages – which did best?

Our results:

What, you thought I’d actually just tell you which one we found worked best? Wrong! Go have some messy fun and find out for yourself (or wait until Episode 7 when we attempt to break the world record for tallest geyser).