* Water: Many hair sprays contain water, which freezes at 0°C (32°F).
* Alcohols: Alcohols, such as ethanol or isopropanol, are also common ingredients. They have lower freezing points than water (e.g., ethanol freezes at around -114°C/-173°F). However, when mixed with water, the freezing point of the mixture is somewhere between the freezing points of the pure components.
* Other Ingredients: Hair sprays also contain polymers, resins, and other chemicals. These can influence the freezing point to some degree, but the primary determinants are water and alcohol content.
If the temperature drops low enough, the water and other freezable components in the hair spray will solidify, causing it to freeze.