Also called liqueur de tirage or filling dosage. Tirage liqueur is needed to initiate the second alcoholic fermentation in traditional bottle fermentation. In order to initiate this fermentation, a mixture of (1) reserve wine, (2) sugar (about 24 g/l), and (3) yeast is added to the base wine. Once this mixture has been added, the base wine is filled into sparkling wine bottles, which are sealed with crown caps. By the end of the second fermentation, the added sugar will completely be fermented by the yeast, producing carbon dioxide as a side product. Since the carbon dioxide cannot escape from the bottle, the still base wine transforms into a bubbly sparkling wine, with small, fine bubbles forming and integrating with the wine. As a result of the carbonation process, the pressure inside the sparkling wine bottle reaches approximately 5 to 6 bars at the end of fermentation. Additionally, the overall alcohol content of the sparkling wine is increased by about 1.5 volume percent.