Secondary fermentation in mead is the stage after the initial vigorous fermentation winds down, where you transfer (rack) your mead into a new vessel to let it clarify, mellow, and develop more refined flavors. Despite the name, it’s not always a true “fermentation” in the active sense. Sometimes residual sugars continue fermenting slowly, but more often this phase is really about aging, clearing sediment, and letting harsh flavors smooth out over weeks or months.
What Happens During Primary vs. Secondary
In primary fermentation, yeast is at its most active. It’s consuming the sugars in your honey-water mixture, producing alcohol and carbon dioxide, and generating a thick layer of dead yeast cells and other sediment (called lees) at the bottom of your fermenter. This stage is loud and bubbly, typically lasting one to three weeks depending on your recipe, yeast strain, and temperature.
Secondary fermentation begins when you siphon the mead off that sediment into a clean vessel, usually a glass carboy or jug. The goal is separation. Leaving mead on heavy lees for too long can produce off-flavors as dead yeast cells break down. Once transferred, any remaining yeast continues working through the last sugars at a much slower pace. The airlock might still bubble occasionally, but the dramatic activity is over. This is where your mead transitions from a rough, young drink into something worth sipping.
When to Rack Into Secondary
The most reliable signal is your hydrometer reading. Most mead makers rack when the specific gravity drops to around 1.010 or lower. A reading below 1.000 (like 0.994 or 0.996) means fermentation is essentially complete, and the yeast has consumed nearly all available sugar. If you started with an original gravity of around 1.074, reaching 0.994 represents full attenuation.
Visual cues help too. When the vigorous bubbling slows to one bubble every 30 seconds or longer, and you can see a clear layer forming above the sediment, it’s a good time to transfer. Waiting too long isn’t catastrophic, but a week or two sitting on heavy lees after fermentation finishes is generally the upper limit before you risk unwanted flavors creeping in.
How to Minimize Oxygen Exposure
Oxygen is the biggest enemy during racking. While primary fermentation produces enough CO2 to blanket the surface and push oxygen out, secondary doesn’t have that protection. Every splash or exposed surface gives oxygen a chance to degrade your mead, potentially turning it stale or vinegar-like over time.
The most practical approach is to use a siphon and keep the output tube submerged below the liquid surface in the receiving vessel. Avoid pouring, and try to fill the secondary container as close to the top as possible to reduce the air pocket (headspace) above the mead. Some mead makers use food-grade CO2 or argon gas to purge the headspace before sealing, which is especially useful if you’re aging for months. Kegs work well for this since you can easily flush them with CO2, though most home mead makers use glass carboys fitted with airlocks, which work fine as long as headspace is minimal.
How Long Secondary Takes
This varies dramatically depending on the style of mead you’re making. Secondary isn’t a single fixed phase. It’s a spectrum from “a few weeks of settling” to “over a year of bulk aging.”
- Session meads (5 to 7% ABV): These lighter meads are drinkable in two to three months and generally peak around six months. They don’t need extended secondary aging.
- Traditional meads (8 to 12% ABV): Plan for six to nine months of aging. Flavors tend to peak around one year, as the alcohol heat softens and the honey character rounds out.
- Sack meads (13 to 18% ABV): These high-alcohol meads require the most patience, often 12 to 24 months. They can taste harsh and hot for the first several months, then transform dramatically around the two-year mark.
- Melomels (fruit meads): Fruit additions can accelerate flavor development. Most peak between six and 12 months, though this depends on the fruit used and how much was added.
You’ll know things are progressing when the alcohol burn mellows, flavors taste balanced rather than one-note, and the mead clears visibly. Some mead makers rack a second or even third time during this period to get the mead off any new sediment that accumulates.
Clarifying Your Mead in Secondary
Time alone will clear most meads. Particles and suspended yeast gradually settle to the bottom over weeks and months, leaving increasingly clear liquid above. But if you want to speed things up or achieve crystal clarity, fining agents can help.
Bentonite is one of the most common options. It’s a type of clay that carries a negative charge, attracting positively charged proteins and yeast cells and dragging them to the bottom. Gelatin works on a similar principle but targets tannins and haze-causing particles from the opposite direction. Some mead makers use a combination approach, adding both bentonite and gelatin (sometimes with egg albumin) to catch the broadest range of particles. These are typically added directly to the secondary vessel and left to work for a week or two before racking the clear mead off the settled material.
Cold crashing is another popular method. Dropping the temperature close to freezing for a few days causes suspended particles to clump together and fall out of suspension faster than they would at room temperature. This works well on its own or combined with fining agents.
Adding Carbonation in Secondary
If you want a sparkling mead, secondary fermentation can serve a different purpose entirely: building carbonation in the bottle. This is called bottle conditioning, and it involves adding a measured amount of sugar to your finished mead right before bottling. The residual or re-introduced yeast consumes that sugar inside the sealed bottle, producing CO2 that dissolves into the liquid.
The standard guideline from the American Homebrewers Association is roughly three-quarters of a cup (about 177 grams) of corn sugar per five-gallon batch to reach moderate carbonation levels of 2.25 to 2.5 volumes of CO2. You can scale this up or down depending on how fizzy you want the result and the size of your batch. Less sugar gives a gentle sparkle, while more creates a champagne-like effervescence.
Bottle conditioning requires bottles rated for pressure, like champagne bottles or thick beer bottles with proper caps. Standard wine bottles can’t handle the pressure and risk shattering. The carbonation process typically takes two to four weeks at room temperature before the bottles are moved somewhere cool to age further.
Backsweetening Before Bottling
Many mead makers find their mead finishes drier than they’d like after fermentation completes. Backsweetening is the process of adding honey or another sweetener to the finished mead to bring the sweetness back up. This is done in secondary, after fermentation has stopped and ideally after you’ve stabilized the mead with potassium sorbate and potassium metabisulfite to prevent the yeast from re-fermenting the new sugar.
A common target for a semi-sweet mead is a specific gravity around 1.015, though this is entirely a matter of personal taste. Add sweetener in small increments, stir gently, and taste as you go. If you skip stabilization and backsweeten, you risk restarting fermentation in the bottle, which can lead to overcarbonation or even exploding bottles.