It’s happened to us all: a soda that’s fallen or been shaken suddenly explodes, making a sticky mess. Dropping or shaking a can of soda portends disaster, and if it doesn’t explode on impact, you’re probably afraid to open it for fear it will. Fortunately, there are tricks you can use that will calm your fear of soda explosion. One of them is giving the can a few taps.
Before we explain, let’s first look at why soda gets so violent when shaken. It’s all about the way the soda is packaged. The gas that makes soda fizzy is carbon dioxide (CO2). In fact, the CO2 in a can of soda means it’s a great addition to cake batter to achieve fluffier results. In the can, the CO2 is placed under high pressure, which changes it from a gas to a liquid — carbonic acid. This is why sparkling water, though hydrating, contains acid that may affect your teeth. You can even taste the acid in a freshly opened can, and this is why canned soda tastes different from fast-food fountain sodas; fountain sodas are mixed by the fountain mechanism to order rather than pressurized and stored, so the fountain soda has no carbonic acid.
When the can or bottle is sealed, the liquid is saturated with CO2 gas or carbonic acid in a pressurized condition, waiting to be activated. There’s still more gas sitting atop the liquid. Opening the can vents some of that gas, causing that telltale “hiss” and activating the carbonic acid within the liquid, turning it into a gas, which creates the bubbles. Of course, there’s another way to activate bubbles: a good shake. This can lead to explosion … unless you try this trick.
How to avoid the effects of a shaken can
When a can is dropped or shaken, the gas dissolved in the liquid is activated, turning back into gas. Before long, the amount of gas between the liquid and the top of the can grows to the point that it just needs to escape and needs somewhere to go, so the can may explode. Opening it right away may lead to an overwhelming amount of bubbles to rise to the top and overflow.
Think about when you open an unshaken can of soda and pour the contents into a glass; the bubbles tend to climb up the sides. This is a process called nucleation, which is the conversion from one state (like liquid carbonic acid) to another (CO2 gas) around a nucleus, such as a speck of dust. When you pour soda into a glass, the microscopic particles on the surface of the glass serve as nuclei, around which the gas bubbles can form. In a can that’s been shaken, imagine tons of bubbles clinging to the inside of the can, preparing to explode out.
But the tapping trick can help stop that process in its tracks. Simply tap the sides (not the top) of the can all the way around — gently. This helps break the bubbles loose from the sides so they can’t continue to nucleate and form more bubbles. Depending on the amount of shaking that’s happened, you can also simply leave the can for a few hours to let the bubbles calm down, or try cooling the can off to lower the energy of the CO2.
