Tank method – also known as cuve close or the charmat process – is a very common method to make sparkling wine. It is developed by Eugene Charmat, hence the name, in 1909.
What is it and how is it different from other methods?
After harvesting, the grapes are pressed directly. The first fermentation takes place in temperature controlled stainless steel tanks to retain the varietal aromatics. The resulting base wines do usually not undergo additional treatment, like MLF or oak ageing. Yeast and sugar is added to provoke the second fermentation in a pressure tank. The fermentation is stopped when a pressure of about 5 atmospheres is reached. This is slightly less than the pressure of 6 atmospheres for traditional method sparkling wine – meaning the latter will usually have a creamier mousse.
Stopping the second fermentation is done by cooling the wine to -5ºC, which also stabilises the wine (and avoids crystal deposition in the bottle). The wine is filtered and optionally liqueur de dosage is added to adjust the sweetness of the wine. The wine is, then, bottled under pressure and ready for take-off.
Pros & cons of this method
The most obvious advantage is that it is much cheaper, faster and less capital intensive than the traditional method. A sparkling wine can be made within two months from grape to bottle. This is a lot faster than the minimal required nine months of ageing for a basic traditional method sparkling wine, like cava or crémant.
The downside of the method is that the end product is less complex, because there’s no autolysis involved. Whereas the traditional method can produce wine that have autolytical flavours of brioche and yeast, the tank method allows the production of sparkling wine that retains the flavours of the base wine. This method is ideal and even preferred for sparkling wines emphasizing fruit and varietal aromatics rather than the flavors derived from autolysis.
Where is it used?
Most Asti DOCG and Prosecco bottlings are produced in this method.