The Infamous Soda And Candy Combo That Launched Thousands Of Science Experiments

On the eve of the 21st century, back before YouTube and Facebook existed, when something that enthralled the collective mind was called a fad rather than a viral video, a chemistry teacher named Lee Marek showed up on "The David Letterman Show" to perform a science experiment on a segment called "Marek's Kid Scientists." It would take years afterward, as well as the help of a few early internet influencers, for the Mentos and Diet Coke sensation to really take hold — and achieve virality — but that was how it began.

There's no need to explain Diet Coke — it's a pretty universally known and understood product — but for those who aren't familiar, Mentos are a sort of chewy candy-coated mint with a unique rounded lens shape. They've been around since the 1930s, but really made a splash in the '90s with nostalgic television commercials and the moniker "The Freshmaker." Both Mentos and Diet Coke are perfectly regular foodstuffs, but when the mints are dropped into a freshly opened bottle of soda, the soda immediately fizzes up all at once, producing a geyser-like effect as it shoots out of the top of the bottle.

For a while there, the internet was awash in Diet Coke geysers, as person after person discovered this impressive effect and entertainers went to stunning lengths with the displays. The folks at EepyBird kicked off the trend, choreographing over 100 bottles at once, and it culminated in 2014 with a Guinness World Record of over 4,300 bottles set off concurrently at a festival in Mexico. The trend even reached the point that urban legends were circulating about individuals dying from the effects of this combination.

Interestingly, while this reaction was first brought into the public eye by a late-night TV presentation from a chemistry teacher, the effect is not chemical at all. Unlike the frothing baking soda and vinegar volcanoes of childhood science labs, the fizz here is actually created by a purely physical reaction, as dissolved carbon dioxide is rapidly released.

Diet Coke, just like all forms of carbonated water, is pumped full of carbon dioxide gas, which dissolves into the solution. When agitated, or when given an imperfect surface to interact with, these dissolved gases form bubbles. If, for example, you drop a small piece of fruit in a carbonated beverage, bubbles will form on the outside, causing it to float to the surface. This process, the forming of gas bubbles, is called "nucleation." As it turns out, those nostalgic '90s candies are just covered in perfect little nucleation sites.

Mentos both look and feel smooth, but when observed at high degrees of magnification, they are actually covered in tiny pits perfect for forming carbon dioxide bubbles in soda. Pair that with the fact that the mints are dense enough to sink to the bottom of the bottle in spite of the heavy bubbling, and you have the perfect tool for creating a soda geyser.

There are countless videos on the internet of this effect, but nothing hits that nostalgia button quite like the real thing. To try this yourself, open a fresh bottle of Diet Coke, roll up seven Mentos in a paper tube, and carefully drop them in all at once. The reaction is pretty instantaneous, so back up quickly or else you might get covered in soda — and be sure to do it outdoors.