Traditional method: Second fermentation

This new blend then has a mixture of sugar and yeast added to it before bottling in particularly strong, dark bottles, usually stoppered with a crown cap, so that a second fermentation will occur in bottle, creating the all-important fizz. Conventionally, an addition or tirage of about 24 g/l of sugar is made. This creates an additional 1.2 to 1.3% alcoholic strength and sufficient carbon dioxide to create a pressure inside the bottle of 5–6 atmospheres after disgorgement (see below), which is roughly the fizziness expected of a sparkling wine, and one which can safely be contained by a wired champagne cork. During this second fermentation, known as prise de mousse in French, the bottles are normally stored horizontally at about 12 °C/54 °F until the fermentation has produced the required pressure and bubbles, usually for four to eight weeks.