Tank method

The steps

1. A still base wine is made: pressing, débourbage and first fermentation.
2. The base wine goes into a closed tank built to hold pressure.
3. Second fermentation takes place in the closed tank, so the CO2 stays in the wine.¹
4. The wine stays in contact with the lees for the required time, in some cellars with stirrers.¹
5. The wine is filtered off the lees and bottled under pressure, with a dosage where needed, and closed with a cork and wire cage.

There is no tirage into individual bottles, no riddling and no disgorgement.

How the CO2 is produced and kept

EU rules allow the secondary fermentation of sparkling wine only in bottles or in closed tanks.¹ For sparkling and quality sparkling wine the CO2 must come only from the alcoholic fermentation of the cuvée.¹ The tank is the pressure vessel: it keeps the gas dissolved during fermentation, and the wine is moved to the bottle under pressure so that the gas is not lost. The wine meets its lees in the tank rather than in individual bottles, and the legal lees times are shorter than for the traditional method; stirrers shorten them further.¹ That is the difference from carbonation, where the gas is added.

Legal minimums

For quality sparkling wines with a PDO made in closed tanks, the production process from the start of the sparkling fermentation, including ageing, may not be shorter than 6 months (9 months when fermentation is in the bottle).¹ The sparkling fermentation and presence on the lees must last at least 90 days, or 30 days in containers with stirrers.¹

Prosecco DOC frizzante may be made either in the bottle or in an autoclave.² The 60-day rule for Rosé comes from the Consorzio technical sheet; the amending decree was not reviewed. Whether the EU 6-month and 90-day minimums apply to Prosecco in practice was not confirmed in a Prosecco-specific text. Sekt Austria Reserve and Große Reserve exclude the tank method.^6,7 Single-fermentation Asti has its own page: Asti method.

Note: the EU durations for tank and bottle production were read in the legislation.gov.uk reproduction of Regulation (EU) 2019/934, Annex II; a 2021 amendment removed figures from part of that annex, so they should be re-checked against the current EUR-Lex text.¹

Label wording

The EU terms "bottle-fermented" and "traditional method" require a second fermentation in a bottle, so a tank-method wine cannot use them.⁸ The usual sweetness terms apply, as for every sparkling wine; see label terms in EU law and the sugar scale.