A wine is considered sparkling when it contains carbon dioxide coming exclusively from the wine's second fermentation, which can take place inside a bottle (Traditional Method) or in a tank (Charmat). The wine should normally have an alcohol content between 10% and 13% abv. and at least 4 atm of pressure. These are the main characteristics that differentiate sparkling wine from the so-called still wine, which is the wine we usually find more often - without bubbles and which is also not fortified.