Secondary fermentation for wine typically takes anywhere from one to six weeks, though it can stretch to several months depending on the type of wine, the temperature, and what you’re trying to achieve. The term “secondary fermentation” means different things in different contexts, so the timeline depends on whether you’re finishing off residual sugars in a carboy, running a malolactic fermentation, or producing a sparkling wine.
What “Secondary Fermentation” Actually Means
In winemaking, secondary fermentation doesn’t have one fixed definition. For home winemakers, it usually refers to the slower phase of fermentation that happens after you rack (transfer) your wine off the sediment into a carboy or other sealed vessel. Primary fermentation is vigorous and fast, often finishing in a week or two. Secondary fermentation is the quieter tail end, where remaining sugars are consumed and the wine begins to clarify.
For commercial winemakers, secondary fermentation most often refers to malolactic fermentation, a biological process where bacteria convert one type of acid into a softer, less tart acid. This is standard for nearly all red wines and common in certain whites like Chardonnay. For sparkling wines like Champagne or Prosecco, secondary fermentation is the step that creates carbonation, either in the bottle or in a pressurized tank.
Timeline for Home Winemaking
If you’re fermenting wine at home in a carboy, secondary fermentation can take anywhere from a few days to several weeks. According to Clemson Cooperative Extension, the wine may clarify in as little as a few days or take several weeks depending on the type. You should check the specific gravity every three days to track progress. Once readings are stable and at or near your target, fermentation is complete.
If you plan to leave your wine in secondary for more than 14 days, use a glass carboy rather than food-grade plastic. Glass lets virtually no oxygen through, while plastic is slightly permeable and can expose the wine to oxidation over time. Whichever vessel you choose, size matters: pick one that closely matches the volume of wine you’re transferring. Excess headspace means more oxygen contact, which can lead to off flavors or spoilage.
For most fruit wines and simple grape wines made at home, expect secondary fermentation to last two to four weeks before the wine is ready to bottle or move into bulk aging.
Malolactic Fermentation Duration
Malolactic fermentation is a different process from alcoholic fermentation, driven by bacteria rather than yeast. It usually begins shortly after primary fermentation ends and can take anywhere from a few weeks to several months. The single biggest variable is temperature. Wine stored in a cool cellar over winter often undergoes a very prolonged malolactic fermentation simply because the bacteria work slowly in cold conditions.
Some Chardonnay producers deliberately allow a slow, late-starting malolactic fermentation in the barrel, letting the wine sit on its sediment (called lees) for weeks or even months. This extended contact in low-oxygen conditions promotes the production of diacetyl, the compound responsible for the rich, buttery flavor some drinkers love in white wine.
What Speeds It Up or Slows It Down
The pH of your wine plays a major role. The bacteria responsible for malolactic fermentation are sensitive to acidity. In wines with a pH below about 3.2, the process can stall or crawl along. At a pH of 3.8 or higher, additional bacterial species can thrive, which speeds things up but also raises the risk of unwanted microbial activity.
Nutrient availability matters too. The lactic acid bacteria that drive this process cannot manufacture their own amino acids and vitamins. They depend on what’s already in the wine. Wines that had extended skin contact during primary fermentation tend to have higher nutrient levels, which gives the bacteria more to work with and generally results in a faster, more reliable malolactic fermentation.
Sulfur dioxide (SO2), the preservative most winemakers add, is the other critical factor. Even moderate levels of free SO2 can inhibit or completely stop malolactic fermentation. At high pH levels (around 3.95), you’d need roughly 79 to 112 parts per million of free SO2 to fully prevent bacterial growth. If you want malolactic fermentation to proceed, you need to hold off on adding sulfites until the process finishes.
Sparkling Wine Secondary Fermentation
For sparkling wines, secondary fermentation is the step where carbonation develops. In the traditional method used for Champagne and many high-quality sparkling wines, this happens inside the sealed bottle. Yeast and a small dose of sugar are added, and the bottle is capped. The yeast consume the sugar, producing CO2 that dissolves into the wine. This fermentation itself takes roughly six to eight weeks, but the wines then age on their lees for months or years to develop complexity. Champagne regulations require a minimum of 15 months of aging on lees, and many producers go well beyond that.
In the tank method (sometimes called the Charmat method), used for wines like Prosecco, secondary fermentation happens in a large pressurized steel tank rather than individual bottles. This approach is faster, often completing in just a few weeks, because the larger volume and controlled temperature make the process more efficient. The resulting wines tend to be lighter and fruitier, which is the intended style.
How to Tell When It’s Done
For alcoholic secondary fermentation, a hydrometer is your best tool. When the specific gravity stops dropping and holds steady over multiple readings taken a few days apart, fermentation has finished. For most dry wines, the final gravity will be somewhere around 0.990 to 0.998.
For malolactic fermentation, you can use paper chromatography kits or send a sample to a lab. These tests show whether malic acid is still present. Once it’s fully converted, you’ll see only lactic acid on the test strip. At that point, it’s safe to add sulfites and move on to aging or bottling.
Patience is the common thread across all types of secondary fermentation. Rushing the process, whether by bottling too early or adding preservatives prematurely, leads to problems ranging from off flavors to exploding bottles. When in doubt, give it another week and test again.