How to make a Diet Coke and Mentos fountain

Not my normal topic I know, but as several people have asked how we created the Diet Coke and Mentos fountain in a video I shared on Facebook today, I thought I’d document it here. Great fun and cheap entertainment for the school holidays as it only cost us 80p ;-)  If you want to know what I’m talking about, here’s the video:

How did we do it?  Well we made a slightly less spectacular version on Periscope earlier in the afternoon when we only used 4 Mentos.  So after a bit of Googling, we worked out a way of getting a lot more Mentos into the bottle at once.

You will need:

  • A two litre bottle of diet cola – You’re not going to want to drink it afterwards so we used the cheapest we could find: Sainsbury’s Basics costing a mere 20p
  • 9 Mentos
  • A piece of paper, approx A5 in size
  • A couple of short pieces of cellotape
  • A large screw
  • A magnet

Method:

  1. Take the top off the bottle of cola.
  2. Roll the piece of paper so that it makes a tube that just fits inside the open top of the bottle. Secure the edges of the tube with cellotape so it doesn’t unroll.
  3. Take the paper tube out of the bottle and put the screw inside the end of the tube, so it’s pointing downwards out of the tube.
  4. Put a magnet on the outside of the tube to hold the screw in place.  The screw is just there to stop the Mentos falling into the bottle until you’re ready, so you need one with a head that’s at least 1/3 of the width of the tube and that’s light enough for the magnet to hold it in place.  I got the idea from another video where they’d used a ball bearing to block the tube so you could try using one of those if you haven’t got a suitable screw.
  5. Drop the Mentos into the tube on top of the screw.  The amount of Mentos the screw will hold without dropping out will depend on the size of the screw and the strength of the magnet.  Our combination would hold 9.  We reckon you’ll need at least 7 Mentos to create a decent sized fountain.
  6. Pop the tube filled with Mentos back into the top of the cola bottle with the screw pointing downwards, being careful not to dislodge the magnet.
  7. When you’re ready to go, take away the magnet.  This releases the screw and the Mentos will fall into the bottle. Stand back and watch the fun, and don’t blame me if you get wet :-)
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