Champagne is bottled at car-tyre pressure - and the bubbles are a second fermentation
The fizz isn't pumped in; it's grown, sealed inside the bottle by yeast eating sugar in the dark.
A bottle of champagne is not simply fizzy wine. In the methode champenoise, still wine from the Champagne region of northeastern France is bottled with a measured dose of sugar and yeast, then sealed. The yeast eats the sugar and slowly converts it into alcohol and carbon dioxide - but with nowhere to escape, the gas dissolves into the wine.
As CO2 builds up, the pressure inside climbs to around 6 atmospheres (about 6 kg/cm2) - roughly three times the pressure in a car tyre. That is why champagne bottles are made of thick, dark glass designed to withstand up to 12 atmospheres, and why a cork can leave at startling speed.
During fermentation the sugar is converted into alcohol and carbon dioxide, and the carbon dioxide causes a relatively high pressure to build up within the hermetically closed bottle.
The wine then ages on the spent yeast for one to three years, the slow, cool fermentation producing the fine, persistent bead prized in a good glass.
Sources & references
2 referencesWell-established. Corroborated by 2 independent sources.
