All. About. Wine.
The Traditional Method (also known as The Champagne Method) invovles taking a finished wine and creating a secondary fermentation inside of the bottle. Once the finished wine is in the bottle, a tirage (a mixture of yeast, sugar and sometimes yeast nutrients) is added. The tirage causes a secondary fermentation inside of the bottle. Since the CO2 from the fermentation has nowhere to go, it is absorbed by the wine, creating bubbles.
Before corking the finished wine, the winemaker must remove the dead yeast cells (also known as lees) from the wine. This is a process called disgorging. It involves freezing the neck of the bottle (where the dead yeast cells have collected), opening the bottle and allowing the frozen lees to shoot out. The winemaker is left with the clear, sparkling wine, which is then capped off with a traditional cork and cage.
This process is time consuming, costly and risky- but it makes for some truly fabulous and one-of-a-kind wines- which is why sparkling wines made in this manner tend to be very expensive. Some of the wines made in this style are Champagne, Cava and Cremant.
Also known as the Tank Method, The Charmat Method tends to be an easier and less-expensive way to produce sparkling wine. Instead of adding the tirage to a bottle, it is added to a pressurized tank (without the pressure, the CO2 would blow-off into the air) of finished wine. The wine goes through its secondary fermentation in bulk. It is then filtered, to remove the lees, and bottled under pressure to retain the bubbles. One of the most famous wines made in this method is Prosecco.
This is the oldest method of making sparkling wine. It is also the method used to create pétillant-naturel (more commonly known as pet-nat).
These wines are not created using a secondary fermentation. Instead, the winemaker bottles the wine before it has completely finished its primary fermentation. The bottle is sealed with a crown cap (just like a bottle of beer) and is allowed to finish fermenting under pressure- thus creating the bubbles. Rarely, the winemaker will disgorge and rebottle. However, it has become increasingly popular to allow the lees the remain in bottle and the resulting wine to remain a bit cloudy. This style has recently become very popular with natural wine fans.
This method does tend to be frowned upon by most winemakers. It simply involves injecting CO2, under pressure, into a finished still wine until the wine has become sparkling (similar to soda).