Many thanks for the article by Tonya Coffey, “Diet Coke and Mentos: What is really behind this physical reaction?” [Am. J. Phys.76(

), 551
(2008)]. The work presented in that paper has greatly enhanced my explanation of that experiment. It is an excellent investigation of how many different liquids react to Mentos, as well as how different substances, from baking soda to sand, cause carbonated diet cola to explode.

I would like to offer my discovery of an excellent method for doing this activity that is cheaper and easier than using Mentos or any of the substances explored in Coffey’s paper. Iron filings have sufficient surface area to cause the rapid nucleation typical of the Diet Coke/Mentos reaction, with the added benefit of being magnetic. While the release of Mentos into several bottles of soda requires advance preparation of the Mentos...

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