The question of whether cotton candy melts or dissolves often leads to confusion about the difference between a physical change caused by heat and one caused by moisture. This airy confection, known for its rapid disappearance, is not actually melting like an ice cube or chocolate bar. Instead, its unique composition makes it highly susceptible to dissolving, turning it from a fluffy cloud into a dense, sugary syrup when exposed to water.
The Unique Structure of Spun Sugar
Cotton candy is composed almost entirely of sucrose, but its physical state gives it its characteristic texture. When sugar is heated to a liquid state and spun through tiny holes, the molten sugar is rapidly cooled upon contact with the air, preventing the molecules from forming their usual crystalline structure. This fast cooling creates an amorphous solid, or a glass-like structure, where the sugar molecules are randomly arranged instead of being in an ordered lattice.
The result is a mass of extremely fine, hair-like sugar threads. This delicate network of sugar fibers traps a vast amount of air, giving the candy its light, fluffy consistency. The sugar itself comprises a very low density, which contributes to its rapid disintegration when eaten. This fragile, high-surface-area structure makes the treat vulnerable to environmental factors.
The Process of Dissolving: Heat vs. Humidity
Cotton candy does not melt in the traditional sense, as melting is a phase transition driven by temperature, such as when ice turns to water. True melting of sugar requires high temperatures, typically around 320°F (160°C), which is far hotter than a warm day. The physical breakdown of cotton candy is instead a process of dissolution, which is driven by the presence of water.
The sugar in cotton candy is hygroscopic, meaning it has a strong tendency to attract and absorb water molecules from the surrounding environment. When the candy is exposed to humid air, the sugar threads begin to pull moisture directly from the atmosphere. As the water molecules are absorbed, they break the bonds holding the amorphous sugar structure together, dissolving the solid sugar into a liquid solution.
This process causes the fine sugar threads to collapse, releasing the trapped air and shrinking into a sticky, syrupy residue. In environments with high relative humidity, such as above 65%, this deflation can happen in under an hour. The rapid collapse is due to the molecular action of water converting the solid sugar into a liquid solution, not heat.
Storage Secrets for Keeping Cotton Candy Fresh
To maintain the fluffy texture of the spun sugar, the confection must be protected from both liquid water and water vapor in the air. This requires packaging that acts as a barrier to prevent the hygroscopic sugar from absorbing ambient humidity.
Airtight containers or thick, sealed plastic bags are the most effective way to separate the candy from the surrounding environment. Storing cotton candy in a cool, dark, and dry pantry at room temperature is the best practice. Refrigeration and freezing should be avoided because temperature fluctuations can cause condensation, introducing the moisture that leads to dissolution. By minimizing exposure to humidity, the delicate amorphous structure of the sugar can be preserved for weeks.