When a sealed can of soda is placed in a freezer, the liquid inside is subjected to temperatures far below its natural freezing point, triggering a destructive physical process. A standard can of soda is primarily water, carbonation (dissolved carbon dioxide), and sugar, all contained within a rigid aluminum shell designed to withstand a specific internal pressure. The moment the water begins to transition into its solid state, the physics of expansion and pressure quickly overwhelm the can’s structural limits, often leading to a messy outcome.
The Science Behind the Burst
The primary cause of the can’s failure is the unique property of water, which makes up roughly 90% of the soda’s volume, to expand as it freezes into ice. Unlike most liquids that contract when cooled, water molecules arrange themselves into an open, crystalline structure that takes up about 9% more volume than the liquid water did. This volume increase within the fixed volume of the aluminum can generates immense internal hydraulic pressure.
The carbonation in the soda plays a compounding role in the pressure buildup. As the water begins to freeze, the carbon dioxide (CO₂) gas, which is highly soluble in cold liquid water, is actively forced out of solution because ice cannot dissolve the gas. This expelled CO₂ collects in any remaining head space or liquid pockets, rapidly increasing the gas pressure. The combination of the expanding ice and the highly pressurized gas quickly exceeds the can’s structural integrity.
The Immediate Consequence: Rupture and Mess
The aluminum can, while strong, has specific points of weakness where the pressure is released. Failure usually occurs at the seams, particularly the top lid seal or the bottom dome, which is designed to flex slightly under normal carbonation pressure. The tremendous internal force either shears a seam or causes the bottom of the can to bulge outward dramatically before rupturing.
The rupture results in a high-pressure expulsion of the contents, often a mixture of liquid soda and icy slush. This sticky, sugary spray coats the inside of the freezer compartment, sometimes freezing instantly into a foam or “stalagmite” formation. Even if the can does not fully burst, the metal will likely deform permanently, resulting in a visibly distended or bulging shape.
Is the Soda Still Drinkable?
After a can has been frozen, even if it did not visibly burst, the quality of the soda is significantly compromised. The carbonation, which provides the characteristic fizziness, will have been largely expelled during the freezing process and will not fully redissolve upon thawing, leaving the soda noticeably flat. Furthermore, the sugar and other dissolved solids are forced out of the water crystals, leading to fractional crystallization, which can make the thawed liquid taste less balanced.
If the can has ruptured or developed a small leak, the contents should be discarded. A burst can may have small, sharp fragments of aluminum mixed into the frozen product, presenting a safety hazard. For a can that is only bulging but remains sealed, it can be safely thawed in a refrigerator. However, due to the loss of carbonation and change in flavor profile, the resulting drink will not taste like a fresh soda.
Preventing the Freeze
To rapidly chill a can of soda without risking a destructive freeze, precise timing or external methods are necessary. When using a standard freezer, a can of soda should not be left for more than 20 to 30 minutes before being checked or removed. Setting a timer is a simple action that prevents the liquid from reaching the critical freezing point.
A more efficient method is to wrap the can in a damp paper towel before placing it in the freezer. The evaporation of the water from the towel dramatically accelerates the cooling process without allowing the internal temperature to drop low enough to freeze the contents. Alternatively, submerging the can in a mixture of ice, water, and salt creates an icy brine that cools the beverage extremely quickly, often in just a few minutes.