A short explanation of the traditional method, from second fermentation to disgorgement.
Champagne is fermented twice. The first fermentation, in tank or in barrel, makes a still base wine — bone-dry, high in acid, generally unremarkable on its own. The second fermentation happens inside the bottle.
The second fermentation
To trigger it, the producer adds a measured dose of sugar and yeast — the liqueur de tirage — and seals the bottle with a temporary crown cap. The yeast eats the sugar, produces alcohol and carbon dioxide, and the CO₂, with nowhere to go, dissolves into the wine under pressure. By the end of the secondary fermentation, the bottle holds about six atmospheres of pressure — three times that of a car tyre.
Lees ageing
The dead yeast cells (lees) settle in the bottle and slowly autolyse — break down — over months or years, releasing compounds that produce the brioche, toasted-bread, and savoury characters we associate with Champagne. The minimum legal ageing on the lees is fifteen months for non-vintage wines and three years for vintage; serious houses go far longer. Krug Grande Cuvée typically rests on its lees for at least seven years.
Riddling and disgorgement
To remove the spent yeast, the bottles are gradually tilted from horizontal to vertical, neck-down, so the lees collect against the cap — a process called remuage (riddling). The neck is then frozen, the cap removed, and the small plug of frozen lees ejected by the internal pressure (dégorgement). The bottle is topped up with a dosage — a small amount of wine and sugar that determines the final sweetness — and finally corked.
Brut wines have less than 12 grams of residual sugar per litre. Extra Brut, less than 6. Brut Nature, none added at all.