Pop Rocks are the fizzy candy that pops in your mouth. Here’s how to make homemade pop rocks using common kitchen ingredients and a look at the science of how they work.
Homemade Pop Rocks Ingredients
The ingredients are pretty basic. What’s important is using a candy thermometer. Without one, you won’t be able to tell when the mixture is the right temperature so you’ll either get gummy, sticky candy (no pop) or else burned candy.
- 2 cups sugar (sucrose)
- 1 teaspoon baking soda (sodium bicarbonate)
- 1/4 cup plus 1 teaspoon citric acid
- 1/2 cup light corn syrup or honey
- 1/4 cup water
- 1 teaspoon flavoring (e.g., cherry, lime, cola)
- 1-2 drops food coloring (optional)
- Either corn starch or confectioner sugar for dusting
Let’s Make Pop Rocks!
- Dust a baking sheet with either corn starch or confectioner sugar. This keeps the candy from sticking to the pan.
- Combine the sugar, corn syrup (or honey), and water in a medium saucepan.
- Cook the mixture until it reaches 300 °F (149 °C).
- Remove the pan from heat and stir in the baking soda, 1/4 cup of citric acid, flavoring, and coloring. This mixture foams.
- While it’s still hot, spread the mixture onto the baking sheet and sprinkle the remaining teaspoon of citric acid over the top.
- Let the candy cool completely (about 30 minutes to one hour).
- Break it into pieces, place it into a plastic bag, and crush it using a rolling pin.
Store homemade pop rocks candy in a sealed container. Humidity dissolves the sugar, making the candies sticky and soft. Damp candies won’t pop or fizz.
How Pop Rocks Work
The candy part of pop rocks work like any other candy. Dissolving sugar in water and heating it drives off water so the candy hardens as it cools.
The popping part of the candy is the gas trapped within the sugar. Both baking soda (sodium bicarbonate, NaHCO3) and citric acid (C6H8O7) are edible ingredients that dissolve in water. They react with one another and form carbon dioxide gas (CO2), water (H2O), and sodium citrate (Na3C6H5O7).
Difference Between Pop Rocks and the Homemade Version
Really, the only difference between homemade pop rocks and the kind you buy at the store is the pressure of the gas inside the candy pieces.
How the Commercial Version Works
Leon Kremzner and William Mitchell’s patent for the “gasified confection” we know as Pop Rocks basically involves a pressure cooker so there is a higher concentration of gas inside the candy and a better “pop.” The commercial product contains sugar, corn syrup, lactose, water, and artificial colors and flavors. The first step is heating the mixture so the water boils away and adding carbon dioxide at a pressure around 600 pounds per square inch (psi). Releasing the pressure instantly shatters the candy into tiny pieces. Each piece contains bubbles of pressurized gas trapped inside the sugar. You can see these bubbles by examining the candy using a magnifying glass. When you put pop rocks in your mouth, saliva dissolves the sugar and the pressurized carbon dioxide suddenly escapes, making a sizzling sound and shooting candy pieces around in your mouth.
The candy can contain a different gas than carbon dioxide. For example, nitrogen, helium, or nitrous oxide also work.
The patent describes ways of improving the candies, too. For example, adding a bit of pectin, gelatin, starch, or agar agar aids sugar’s ability to hold carbon dioxide as it cools and solidifies. There’s nothing particularly special about table sugar or sucrose as the main ingredient, either. Other types of sugar work. So, in your homemade pop rocks, experiment with different sugars and other ingredients.
Probably the hardest ingredient to find is citric acid. Most grocery stores sell it, but it’s usually grouped with canning supplies. It’s also a key ingredient in homemade bath bombs, so check the pharmacy section. Substitutes include other edible weak acids, such as fumaric acid, tartaric acid, or lactic acid. Vinegar (weak acetic acid) likely works, but if you use it, subtract the liquid volume from the amount of water in the recipe. Of course, substitutions affect flavor.
- Berry, Steve; Norman, Phil (2014). A History of Sweets in 50 Wrappers. London: The Friday Project. pp. 86–87. ISBN 9780007575480.
- Davis, Craig M.; Mauck, Matthew C. (2003-05-01). “Titrimetric Determination of Carbon Dioxide in a Heterogeneous Sample (“Pop Rocks”)”. Journal of Chemical Education. 80 (5): 552. doi:10.1021/ed080p552
- Kremzner, Leon; Mitchell, William A. (December 12, 1961). “Gasified confection and method of making the same.” U.S. Patent Office.