One sachet of Pop Rocks contains sugar crystals holding gas pressurised to roughly 40 times normal atmospheric pressure, which is exactly what makes them crackle the instant they hit a wet tongue.
How Pop Rocks Are Made
Sugar syrup is cooked to a hard-crack stage at around 150degC, then carbon dioxide gas is injected into the molten candy under high pressure, roughly 600 psi. As the candy cools and hardens under that pressure, the gas gets locked inside as thousands of microscopic bubbles. The hardened sheet is then cracked into the small, oddly shaped pieces you see in the packet, each one sealing in its own pocket of pressurised gas.
The Chemistry of the Pop
Once a piece of Pop Rocks meets saliva, the sugar shell around each gas pocket dissolves and ruptures, releasing the trapped carbon dioxide with an audible crack. Multiply that by the hundreds of tiny pieces in a single sachet and you get the sustained crackling sensation. This is a purely physical release of pressurised gas, which is a different mechanism to the acid-and-bicarbonate fizz used in other fizzy sweets.
History and the Pop Rocks Myth
- 1956 — invented by William A. Mitchell at General Foods, who also created Tang and Cool Whip.
- 1975 — finally launched commercially, after new packaging and manufacturing processes were developed to keep the pressurised candy stable.
- The Mikey myth — a persistent urban legend claimed a child actor died from mixing Pop Rocks with cola. It was false, and General Foods ran a public campaign, including letters to schools, to debunk it.
You will still find the original American brand alongside other American candy and snacks.
Frequently asked questions
What makes Pop Rocks pop?
Pop Rocks pop because tiny pockets of pressurised carbon dioxide gas are trapped inside the candy during manufacturing. When saliva dissolves the sugar shell, the gas escapes and creates the crackling sound.
Who invented Pop Rocks?
Pop Rocks were invented in 1956 by General Foods chemist William A. Mitchell, though the candy was not sold to the public until 1975.
Is it true Pop Rocks and soda can make your stomach explode?
No, this is a myth. The gas released is a small amount of carbon dioxide, similar to a fizzy drink, and is not dangerous when eaten as intended.