The Tank method is sometimes called the Charmat or Prosecco method – they are one and the same. It is simply referring to the fact that the wines made in this way have undergone their second fermentation in a tank, instead of a bottle.
All wines made anywhere in the world must go through a basic process from grape to wine – pressing of the juice and fermenting of that juice. Most wines stop at this point being sent to oak or tanks to mature, or just being sent straight to the bottling line. All sparkling wines differ in that they don’t just stop there they will all undergo a second fermentation. Tank method-produced wines undergo that second fermentation in a tank and wines produced in the Methode Traditionelle method undergo it in bottle.
Unlike the wines that are bottle-fermented (Methode Traditionelle) who develop all their flavours thanks to their contact with the lees – a by-product of the second fermentation. The longer they spend in contact with lees, the more flavourful they become. Before the bottle-fermented wines get to the secondary fermentation point they are often very neutral with all flavour solely coming from the lees contact. Tank method-produced wines already have their flavour sorted before they get to the point of second fermentation. Thus it is the more aromatic grapes that are used in making tank method sparkling wines.
The process is roughly the same, that in order to start a second fermentation the base wines must get a bit more sugar and yeast to kick start it. In tank method wines the yeast and sugar is added to a large tank filled with the base wine. As there is a larger volume of wine to deal with the resulting wines won’t get much, if any, flavour from the lees. For tank-fermented wines the secondary fermentation is purely to introduce bubbles into the wines – a very technical ‘soda-stream’-like process.
Classic wines made in this style are: Moscato d’Asti and Prosecco. A general rule is that sparkling wines under the $20 price point will be tank – there are examples over this price point, but many tend to be bottle-fermented at higher price points.