The temperature at which a bottle of champagne is stored affects the formation of the grey-white cloud of fog normally formed on opening, according to a study in Scientific Reports this week.

On popping open a champagne bottle, the gas mixture gushing from the bottleneck experiences adiabatic expansion (an expansion of the gas that causes a drop in temperature), and therefore cools adjacent air packages, thus causing condensation of water vapour found in the ambient air in the form of a characteristic grey-white cloud of fog. However, this process may be more complex than previously thought.

Gerard Liger-Belair and colleagues used high-speed video imaging to visualize cork popping and the condensation process in the bottlenecks of transparent champagne bottles stored at different temperatures (6, 12 and 20°C). The authors found that the temperature of the bottle played a role in the condensation process leading to the formation of the grey-white cloud. For the bottles stored at 20 °C, the characteristic cloud disappeared and was replaced by a more evanescent blue plume, starting from inside the bottleneck. The authors propose that after adiabatic expansion of the gas mixture following the cork popping, clusters of ice water appear in the bottlenecks of the bottles at all storage temperatures. However, at higher temperatures, freezing of gas-phase CO2 occurs on ice water clusters resulting in the blue phase observed at 20°C.