At this point, I don't think we can call them experiments anymore. Unless you've been living in a cave for the last two years, you should already know what happens when you drop a Mentos mint candy into a bottle of soda.  Nonetheless, it seems we never tire of seeing it.

The theme of a recent birthday party at our house was Science Experiments. On the list of activities were making slime, experimenting with cornstarch and water, experimenting with milk and food coloring, tiedying t-shirts, and the grand finale of Diet Coke and Mentos. The task of setting this last part up was mine. Oh, happy day, I love this sort of stuff.

Do a search for mentos and diet coke on YouTube and you'll find dozens of examples. Save yourself the time, they all pale in comparison to the masters from Eepybird. Beyond videos, there are many websites that include pictures and instructions of varying level of detail about how to do your own demonstration. There are even several products on the market now expressly designed to drop candy into soda bottles and direct the resulting fountain.

I watched the videos, read the instructions, looked at the products and made my plan. I would not be investing any money beyond the actual soda and candy. The rest would from everyday household objects and ingenuity.

Materials:

(3) 2 liter bottles of diet coke
(5) 16oz. bottles of diet coke
44 mint mentos (8 for each 2 liter bottle, 4 for each 16oz bottle)
16 large paper clips (to hold the mentos and the 'triggers')
string for pulling the 'triggers'
cardboard box for holding bottles
dirt or sand to pack around bottles to hold them in place

Tools:

Drill and assorted sizes of drillbits
Wire clippers
Pliers
Trowel

The whole process didn't take long. I did most of the work the day before the party. I gathered up some extra bottle caps to prepare the 'triggers' so that I could leave the soda bottles unopened until just before setting off the display.

Step 1: Straighten out 1 paper clip per bottle of soda. Put small bend at end.

Step 2: Drill a small hole (1/16") through all of mentos. This is tedious and somewhat sticky work. I tried doing a few at a time but it didn't work well.

Step 3. Thread mentos onto prepared paper clips.  More mentos means bigger reaction, but only to a point, and you have to suspend the mentos above the soda inside the top of the bottle. I decided that 4 for the small bottles and 8 for the large bottles would be enough and not require removing too much soda.

Step 4. Drill holes in bottle caps. I used various sizes bits and drilled multiple holes in some of the caps. Tiny holes= long-lasting spray. Large holes= short-lived fountain.
Step 5. Make triggers. 1 per bottle. Straighten out 1 bend of  a paper clip, tie about 18" of string to clip.

Step 6. Trim and bend open end of wires holding mentos to make small loops. Make the end as short as possible so the mentos are tucked up into caps as much as possible. Leave the bend open enough to fit end of paper clip through but make sure the wire fits easily through hole in bottle cap.

Step 7. Assemble. Put looped end of wires through caps, put straightened ends of 'triggers' through bend of wire to retain mentos in bottle cap.

All of the work thus far can be done well in advance of the display.
The steps from here should be done just before 'launch'.

Step 8. Prepare soda bottles.  Open them up, pour out just enough soda to allow mentos to be inserted without touching soda. Replace caps on bottles.

DO NOT 'ARM THE DEVICE" yet.

Place bottles in cardboard box. Pack in dirt or sand to hold them in place.
Optional: drill holes in bottles above soda to divert spray outward. I did three holes in a few of the bottles. Make sure the spray from these holes will not hit side of box or other bottles. I added a few inches of dirt to the box to ensure the holes were above the edge of the box.

Step. 9. Place bottles in location for launch. Do this before loading the mentos. Consider trajectory and distance. I left about a 20 ft. radius but you decide...

Step 10. ARM THE DEVICE. Double check that the triggers are secure, remove caps from bottles and screw on mentos-loaded caps. Arrange trigger strings for orderly sequence or just gather them all together.

MAKE SURE THE VIDEO CAMERA IS RUNNING AT THIS POINT.

Pull the triggers, step away and revel in the glory of a soda fountain.

In hindsight, the one thing I would note is that the 16 oz bottles didn't provide much  enough 'oomph' and weren't worth the effort. I'd just go with 2 liter bottles next time.

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