How much pressure is in a bottle of champagne?

About 6 bar of overpressure, measured in a 0.75 litre bottle after the second fermentation in the bottle has finished.

Researchers at the University of Reims published a model in the journal Beverages for the pressure in traditionally made sparkling wine. After the prise de mousse they arrive at about 6.1 bar in a 0.75 litre bottle.

The pressure arises because the yeast in the closed bottle converts sugar and the carbon dioxide has nowhere to go. The more sugar goes in at the tirage, the higher the final pressure.

European regulations require at least 3 bar of overpressure at 20 degrees for sparkling wine and at least 3.5 bar for quality sparkling wine.

Champagne, cava and crémant all three fall under quality sparkling wine and so must reach that 3.5 bar. The measurement is taken in the closed bottle at 20 degrees.

Some appellations set the bar higher. The product specification of Crémant d’Alsace requires at least 4 atmospheres at 20 degrees after disgorging.

Semi-sparkling wine has by definition 1 to 2.5 bar of overpressure at 20 degrees and thus falls into a legal category of its own.

At that lower pressure the bottle does not need a champagne cork with a muselet, and an ordinary closure is often enough. In the glass you see a fine prickle instead of a persistent mousse.

Anyone who opens a bottle expecting the pop of champagne should therefore pay attention to the category. Semi-sparkling wine and sparkling wine are legally two different products.

Carbon dioxide slowly escapes through the cork, so the pressure in a closed bottle drops during years of ageing.

The model from Beverages calculates when an old bottle falls below the legal limit of 3.5 bar. The longer the bottle lies and the smaller it is, the sooner that moment comes.

A magnum has less cork surface per litre of wine than a 0.75 litre bottle and therefore loses its carbon dioxide more slowly. That is a reason to buy bottles that are to be kept for a long time in a large format.

Hold the cork, turn the bottle rather than the cork, and never point the neck at anyone or at a lamp.

First chill the bottle to between 8 and 10 degrees. The Comité Champagne recommends putting the bottle in a bucket of water and ice for twenty to thirty minutes. More carbon dioxide stays dissolved in cold wine, so the gas is released more calmly.

Keep your thumb on the cork from the moment you loosen the wire. A bottle under 6 bar will otherwise release the cork on its own.