What Makes Pop Rocks Pop?

Eating most candy isn’t complicated: You take a bite, enjoy a sugar-fueled dopamine rush, and repeat until you have a stomach ache. Chemist William A. Mitchell added another step to the process when he developed Pop Rocks. When the sweet, hard candy bits hit your mouth, they act up before breaking down, creating a crackling, hissing noise that would be alarming coming from any other food product. But when it happens to Pop Rocks, you know you’re getting what you paid for. So what exactly is it about the candy that makes it just as much of a science experiment as a sweet snack?

The answer lies in carbon dioxide. It’s the same gas that gives cola, beer, and champagne their effervescence, but it’s not a common ingredient in solid foods. In the late 1950s, Mitchell wondered if it was possible to create an instant soda tablet by baking CO₂ into candy. Even though his idea didn’t take off, the experiments laid the basis for Pop Rocks.

Like other hard candies, Pop Rocks are made by mixing sugar, lactose, corn syrup, and flavorings. Once those ingredients are melted together and boiled, highly-pressurized CO₂ is added. When the candy mixture hardens, it traps bubbles of gas exerting pressure at 600 pounds per square inch (psi). For reference, the pressure inside a champagne bottle measures in at 90 psi.

It’s impossible to detect the special component in Pop Rocks unless you taste them. Magical things happen when the candy meets up with your mouth: As your saliva dissolves the sugar, those powerful air pockets begin to burst like miniature firecrackers on your tongue. The 600 psi carbon dioxide collides with the 15 psi pressure of the atmosphere, resulting in a crack you can feel and hear. That’s why Pop Rocks are so noisy, whether you’re eating them or standing next to someone who is.

And if you’re worried that all that pressure will do some serious damage to your body, you can rest easy. Contrary to the hysteria from kids and parents, there’s never been a known case of death by Pop Rocks. That includes when it's mixed with Coke (sorry Mikey truthers).

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