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Mentos and Diet Soda Tuesday, May 20 2008

Maybe the first time you saw it was in that movie, "Urban Legends," or maybe you have no idea what that movie is, but chances are you've heard of the Mentos and diet soda explosion. Basically, someone eats a bunch of mint flavored Mentos then chugs a diet soda and there is a violent reaction (it must be MINT Mentos and DIET cola). The legends are many and varied, but many end in a stomach tearing or someone vomiting or some other such nonsense.

In the movie, a professor is teaching an urban legends class. He has the smartass kid come up front and eat Mentos then drink soda, to prove the myth is untrue. The kid takes a mouthful of both, but doesn't swallow, instead he lurches around a bit before spitting out the mouthful of mush. Everyone laughs the teacher looks dumb, la,la,la.

The MythBusters team has tried several Mentos and soda myths and although they have been able to prove that there is a violent reaction, they have never proved it would explode in your stomach, or cause any reaction other than a burp.

In last week's episode, Tory, Kari and Grant tried to blow up a pig stomach, filled with a human stomach acid like substance. No matter what they did, they were unable to cause it to rupture and had to resort to using an air hose. The conclusion was that the act of drinking the soda releases the carbon dioxide, which is what causes the reaction.

You've probably caught at least one of the Mentos shows, if you watch MythButers with any regularity. So, where did this all start?

The first person I could find related to the phenomenon was Steve Spangler who appeared on Denver's KUSA-TV in 2002 and 2005. Spangler was science teach, who decided to become a hands on science guru, traveling the country performing science.

The experiment was then further popularized by the website Eepybird.com, which showcased a video of two men re-creating the fountain display seen in front of the Bellagio Hotel in Las Vegas using a timed series of eruptions. The site also showed soda jets linked together to form a Domino Rally-style effect. Both of these videos were shown on MythBusters when Adam and Jamie first tried to prove the myth and then recreated their own domino effect.

The MythBusters also created what is believed to be the highest soda jet recorded, at over 29 feet (9 meters), using a nozzle fitted into the mouth of the bottle, although it was never made official and there are groups who claim to have beaten the record.

There are various theories that are debated as to the exact scientific explanation of the phenomenon. Perhaps the most widely used explanation is that there is a physical reaction and not a chemical one. To form a new bubble, water molecules must push away from one another. It takes extra energy to break this surface tension. So, in other words, water resists the expansion of bubbles in the soda.

Each Mentos candy has thousands of tiny pores all over its surface. These tiny pores function as nucleation sites for carbon dioxide bubbles to form. As soon as the Mentos enter the soda, bubbles form all over their surface. Then, as they sink to the bottom, carbon dioxide is released by the carbonated liquid with which they come into contact along the way.

The gang concluded that the reaction was caused by the caffeine, potassium benzoate, aspartame, and CO2 gas contained in the Diet Coke and the gelatin and gum arabic ingredients of the Mentos. In addition, they theorized that the physical structure of the Mentos is perhaps the most significant cause of the eruption. When flavored Mentos with a smooth waxy coating were tested in carbonated water, no reaction occurred, but when they added Mentos there was a small eruption. This was further supported when rock salt was used as an effective substitute for Mentos.

So, there's the science.

The urban legend first started in 1979. It was reported at the time that a child, whose name was unspecified, had gulped down a soda after eating Pop Rocks, a carbonated candy known for creating a popping sensation in the mouth. According to the legend, the reaction was so violent, the child’s stomach exploded and he died.

Later the story was amended to specify the tot as Mikey from the LIFE cereal commercials. Mikey is. from all accounts, still alive and well. Over the years emails have been sent about unspecified children in Brazil or Japan or some other country where it would be hard for the average Joe to verify it, exploding from Mentos or Pop Rocks and diet soda. Despite the fact that these myths have been debunked over and over again, an exploding kid makes for a good myth and so it stays around. None of these stories have ever been proven and there is no record of any media outlet covering a story like it.

The videos are still out there and the fear is still high, but thanks to the gang at MythBusters, you can feel a little safer cramming down a pack of Mentos and chugging a diet soda. Although if you do explode, don’t blame me.