The traditional method — méthode traditionnelle — is the most labour-intensive route to bubbles. A base wine ferments dry in tank or barrel. Then a blend of wine, sugar and yeast (liqueur de tirage) is added and the wine is bottled under a crown cap. The second fermentation happens inside the bottle, generating carbon dioxide that cannot escape — it dissolves into the wine and creates fine, long-lasting bubbles.
The bottle is then aged on its side, often for months or years. The yeast lees break down (autolysis) and contribute notes of brioche, toast and biscuit. Finally the lees are gathered into the neck (remuage), frozen and expelled (dégorgement), after which a small measure of wine and sugar (liqueur d'expédition) is added before the cork is fitted. The method is used for Champagne, Cava and Crémant.