How Sparkling Wine Is Made

Where the bubbles come from

Bubbles in sparkling wine are carbon dioxide dissolved in the liquid under pressure. It is produced during a second alcoholic fermentation that takes place in a sealed container, so the gas cannot escape. When the bottle is opened, the pressure drops and the gas is released as bubbles.

The traditional method

Used for Champagne, Crémant, Cava and many other fine sparkling wines, the traditional method (méthode traditionnelle) carries out the second fermentation inside the bottle in which the wine is sold. A base wine is bottled with a mixture of sugar and yeast, called the liqueur de tirage, and sealed with a crown cap.

During the months or years that follow, the yeast cells die and form a sediment called lees. Contact with the lees gives the wine its characteristic brioche, biscuit and toasted-nut aromas and a creamy texture. Under the rules of the Champagne appellation, non-vintage cuvées must age for at least 15 months in total, including at least 12 months on the lees, while vintage cuvées must age for at least three years.

Removing the sediment

• Riddling (remuage): bottles are gradually rotated and tilted neck-down so the sediment slides into the neck. Today this is largely done by machine.
• Disgorgement (dégorgement): the neck is frozen, the crown cap is removed and the plug of sediment is expelled by the pressure.
• Dosage: a small amount of wine mixed with sugar tops up the bottle and sets the final sweetness level before the cork is inserted.

The tank method and other approaches

In the tank method (Charmat or Martinotti), the second fermentation takes place in a large pressurised steel tank and the wine is then bottled under pressure. It is faster and cheaper, and keeps the fresh, fruity character of the grapes, which is ideal for Prosecco and Asti.

Other approaches include the ancestral method (pét-nat), in which the wine is bottled before the first fermentation has finished so it completes in the bottle, and the transfer method, which combines bottle fermentation with tank filtering.

Reading the sweetness on the label

• Brut Nature: no added sugar, bone dry.
• Extra Brut and Brut: dry, the most common styles.
• Extra Dry: slightly sweeter than Brut despite the name.
• Sec, Demi-Sec and Doux: progressively sweeter.