Everyone's heard that adding Mentos to Diet Coke produces a strong reaction, but there are few details available about how to coordinate the parts to get a good geyser.
EepyBird.com has a great video of a Bellagio-like fountain of Diet Coke + Mentos reactions. They also have instructions for creating your own.
This is how we implemented the EepyBird system.
You need these parts:
1) some number of two-liter bottles of soda (Diet Coke seems to be preferred).
2) A box of Mentos.
3) A few paper clips.
4) A drill.
First: drill a hole in the cap of the soda bottle. We tried two sizes. The smaller one made a spray, and the larger (5/32") made a nice thin geyser stream.
Next, straighten a paper clip, with a small angle at the end, like a very long thin L. This will hold the Mentos in the neck of the bottle.
Drill some small holes through the center of the Mentos. These need to be large enough to put the paper clip through.
Thread the Mentos onto the paper clip holder. The foot of the L will hold them on.
Finish the stack with the bottle cap.
Clip another paper clip across the holder so that when the bottle cap is screwed onto the bottle, the Mentos are suspended over the soda.
Time to head outside to try it all out!
Insert the Mentos cartridge into the neck of the bottle. Depending on how many Mentos you use (nine is good for a two-liter bottle), you may need to spill out a little soda. It's important that the Mentos not touch the soda!
Carefully screw the top on tightly.
Now pull off the upper paper clip, and stand back!
Here you can just make out the very beginning of the reaction.
If all went well, you'll get a geyser 10 to 20 feet high, that lasts for 20 to 30 seconds!
That straight white line in the photo is a strong geyser of diet coke.
When everything settles down, most of the two liters of soda has been ejected out the top of the bottle.
I made this story with Tabblo, a great way to put your photos on the web and share them with the people you want.