After the first fermentation creates the base wine, the chef de cave adds a precise mixture of sugar, yeast, and reserve wine called the liqueur de tirage. This mixture goes into each bottle along with the wine, and the bottles are sealed with a crown cap—the same kind used for beer bottles. The yeast begins consuming the added sugar, producing alcohol and carbon dioxide. Since the CO2 has nowhere to escape, it dissolves into the wine under pressure. This fermentation continues for weeks in the cool 50°F cellars, where temperature stability is crucial. The yeast eventually dies, creating a sediment called lees that will remain in contact with the wine for months or years, contributing to Champagne's distinctive brioche-like aromas.
This secondary fermentation is what separates Champagne from simple sparkling wine made by injecting CO2. The slow, natural process creates smaller, more persistent bubbles and develops complex flavors that can't be replicated any other way. The longer the wine stays on its lees, the more sophisticated it becomes—which is why prestige cuvées age for years before dégorgement. The pressure created—about six atmospheres—is what gives Champagne bottles their distinctive thick glass and deep punt.
Now you know what's in the glass. Find the bottle that belongs in yours.
Find your Champagne moment →The chef de cave must calculate the exact amount of sugar to add—typically 24 grams per liter—to achieve the desired pressure without risking bottle breakage. Too little sugar means insufficient bubbles; too much can cause bottles to explode in the cellar. They also decide when to perform dégorgement, balancing the development of lees character against the wine's freshness. Some houses, like Krug, age their wines on lees for decades, while others prioritize bright, youthful character with shorter aging.
Those fine, persistent bubbles you see rising in your flute are the direct result of this slow fermentation. Machine-made bubbles are larger and disappear quickly. Natural fermentation creates bubbles that form elegant trains from specific nucleation points in the glass—often microscopic fibers or imperfections. The mousse should feel creamy on your tongue, not sharp or aggressive. If you taste bread, brioche, or toasted nuts, you're experiencing the flavor compounds created during those months on lees.