There are four main methods of sparkling wine production.
The first is simple injection of carbon dioxide (CO2), the process used in soft drinks.
The second is the Metodo Martinotti created and patented by Italian Federico Martinotti (1860-1924) in 1895 and adapted by Eugène Charmat in 1907, a French vine grower in Saint-Pourçain-sur-Sioule, in which the wine undergoes a secondary fermentation in bulk tanks, and is bottled under pressure. This method is used for Prosecco and Asti in particular.
The third method is the traditional method or méthode champenoise.With this method the effervescence is produced by secondary fermentation in the bottle. As the name suggests, this is used for the production of Champagne, but is slightly more expensive than the Charmat process.
The fourth method is the "transfer method". This method will take the cuvée to bottle for secondary fermentation, which allows for the additional complexity, but then will transfer the wine out of the individual bottles into a larger tank after it has spent the desired amount of time on yeast.