How is effervescence created in sparkling wine?

Effervescence in sparkling wine is primarily created through a secondary fermentation process. This method involves a base wine that undergoes a second fermentation in the bottle. During this stage, yeast and sugar are added, which ferment and produce carbon dioxide. Because the carbon dioxide has no place to escape, it dissolves into the wine, creating the characteristic bubbles when the bottle is opened.

This process is most notably known as the méthode champenoise or traditional method, commonly used for wines such as Champagne. It is distinct from artificial carbonation, which involves injecting carbon dioxide gas into the wine, and from simply adding sugar during fermentation or chilling the wine before bottling, neither of which contribute to the natural effervescence in the same integral way that a secondary fermentation does.