Homemade Wine Stopped Fermenting? 6 Causes and How to Fix Each

First — Is It Actually Stuck? (Hydrometer Check)

Homemade wine stopped fermenting — or at least, that’s what it looks like. Before you do anything else, grab your hydrometer. I cannot stress this enough. The first time my blackberry wine went silent on day four, I panicked, repitched yeast, added nutrients, and generally made a mess of things. Turns out the fermentation was completely done. I’d used a high-gravity must and a fast-acting yeast, and it had simply finished ahead of schedule. I wasted two packets of Lalvin EC-1118 and a whole afternoon.

Here’s the diagnostic test that rules out half of all “stuck” cases: take a hydrometer reading and check your specific gravity (SG). If your SG reads at or below 1.000, fermentation is finished. Done. The wine is clearing, not stalling. A reading of 0.994 to 0.998 is completely normal for a dry wine that has fully fermented out.

If your SG is still sitting above 1.010, you have a genuinely stuck fermentation and you need to figure out why. The sections below cover every real cause — diagnosed in a specific order — so you’re not guessing.

Take two readings 48 hours apart. If the number doesn’t move at all, the fermentation is stuck. If it drops even a point or two, it’s just slow. Slow and stuck are not the same problem, and they don’t get the same fix.

Cause 1 — Temperature Drop

This is the most common cause of a stuck fermentation, and it’s the one most people overlook because the fix seems too simple. Wine yeast has a working temperature range. Most strains — Lalvin 71B, EC-1118, Red Star Côte des Blancs — ferment best between 65°F and 75°F (18°C to 24°C). Drop below 60°F and most strains slow to a crawl. Below 50°F, they go dormant entirely.

Basements are the classic culprit. You start a batch in September when the basement is 68°F, and by mid-October it’s 54°F down there. The yeast doesn’t die — it just stops working. This is actually good news, because it means the fix is straightforward.

How to Diagnose It

Use a stick-on aquarium thermometer on the side of your fermenter. They cost about $2 at any pet store or on Amazon. Read it at the level of the liquid, not the top of the vessel. A fermentation that stalled after a cold snap outdoors or a sudden weather change is almost certainly a temperature issue.

How to Fix It

Move the fermenter to a warmer location — ideally somewhere stable between 68°F and 72°F. A spare bathroom works well. An interior closet is even better. Then, wrap the fermenter in a towel or use a seedling heat mat set to low underneath the vessel. The Vivosun 10″×20.75″ heat mat (around $15 on Amazon) works well for one-gallon jugs and smaller carboys. For a 5-gallon carboy, the larger 20″×20″ version is more effective.

Give it 24 to 48 hours after warming up. In most cases, you’ll see bubbling resume without adding anything new. If it doesn’t restart within 48 hours of being at proper temperature, move to Cause 2.

Cause 2 — Yeast Died or Never Started Properly

Yeast death happens. It’s not a failure on your part — not always, anyway. Yeast can arrive in a packet that was stored too warm at the retailer. It can be killed by must that was still too hot when you pitched it (above 95°F kills most strains fast). It can simply fail to take hold if the packet was old or the rehydration step was skipped on a dry yeast.

Frustrated by a fermentation that showed zero activity after 72 hours of warming, I once pulled out a packet of Lalvin EC-1118 I’d had in a drawer for about 14 months. The expiration date had passed. That was the whole problem.

How to Diagnose It

Check your original yeast packet’s expiration date. Then check your pitch temperature — did you add the yeast when the must was cooler than 105°F? Did you rehydrate dry yeast in water between 104°F and 109°F for 15 minutes before pitching, as most manufacturers recommend? If any of those steps went wrong, the yeast likely never established properly.

How to Fix It

Repitch with a fresh, in-date packet of yeast. For restart situations, Lalvin EC-1118 (Champagne yeast) is the industry standard recommendation. It’s aggressive, alcohol-tolerant up to about 18%, and reliable. A single 5g packet costs roughly $1.50 at most homebrew shops. Rehydrate it properly in 104°F water with a pinch of Go-Ferm (a rehydration nutrient), let it sit for 20 minutes, then slowly acclimatize it to the temperature of your must before pitching. Don’t just dump cold yeast into warm wine.

Cause 3 — Nutrient Deficiency

This one is genuinely underserved in most winemaking guides, and it hits fruit wine makers especially hard. Grape juice is naturally rich in the nitrogen compounds, vitamins, and minerals that yeast need to stay healthy through fermentation. Most fruit wines are not.

Peach wine is one of the worst offenders. Peaches are low in yeast-assimilable nitrogen (YAN) and can stall out around 1.030 to 1.020 even with healthy yeast at good temperatures. Blackberry wine stalls frequently at the same range. Elderflower wine — which is made from sugar water infused with flower heads rather than fruit juice — has almost no inherent nutrients at all. Dandelion, apple, and pear wines are similarly lean.

How to Diagnose It

If your fermentation started fine, got to about the halfway point, and then slowed or stopped — especially in a fruit wine made from the types listed above — nutrient deficiency is the likely cause. Temperature is fine, yeast is alive, but the yeast simply ran out of fuel to finish the job.

How to Fix It

Add yeast energizer (not just yeast nutrient — energizer contains diammonium phosphate, magnesium sulfate, and B vitamins that nutrient alone doesn’t). Fermaid-O and Fermaid-K by Lallemand are the go-to products for serious home winemakers. For a quick fix, Homebrew Heaven’s generic yeast energizer works fine and costs about $3 for a 1-oz packet. Add it at the rate of 1/2 teaspoon per gallon, stir well to degas the wine first, and allow 24 to 48 hours for the yeast to respond.

Cause 4 — Too Much Sugar at Start

This one is harder to fix, and it’s worth being honest about that upfront. When a must starts with a specific gravity above 1.120 — roughly equivalent to a potential alcohol of 16% or higher — the yeast can lock up from osmotic pressure before fermentation even gets going well. The high sugar concentration pulls water out of the yeast cells through osmosis. The yeast are essentially dehydrated from the outside in.

Some winemakers chase high-alcohol wines and add sugar in stages to avoid this problem. If you added all the sugar at once and started above 1.120, you may have created a wine that the yeast simply cannot finish at full gravity. Fortified-wine territory — ports, for instance — works around this by stopping fermentation intentionally and adding spirits. That’s not a bug; that’s the design.

Why This Is Hard to Fix

By the time you realize the fermentation is stuck from sugar lock, the wine is already high in alcohol and sugar. Adding more yeast often doesn’t help because the new yeast faces the same osmotic environment. The most viable path is diluting the wine with water or unsweetened juice to bring the residual sugar down, then repitching EC-1118. Expect some flavor dilution. It’s an imperfect fix for an avoidable problem — next time, start no higher than 1.110 and step-feed additional sugar after active fermentation begins.

Cause 5 — CO2 Still Dissolved

Probably should have opened with this section, honestly — or at least put it higher. It catches a lot of beginners off guard.

Active fermentation produces CO2. That CO2 has to go somewhere, and during fermentation it exits through the airlock. But once primary fermentation ends, a significant amount of CO2 stays dissolved in the wine itself. It doesn’t leave just because fermentation stopped. The airlock goes quiet, the wine looks still, but it hasn’t actually stalled — it’s just done producing gas faster than it’s releasing it.

How to Diagnose It

Take a hydrometer reading. If SG is at or below 1.000, the wine is done and the “stuck fermentation” is actually just dissolved gas behaving normally. You can confirm CO2 saturation by gently stirring the wine — you’ll see fine bubbles rise to the surface, more than you’d expect from a fully still liquid.

This is not a problem to fix. It resolves on its own during bulk aging, or you can degas the wine intentionally using a drill-mounted degassing whip (the FastFerment brand ones run about $12) before bottling.

Cause 6 — Campden Tablets Killed the Yeast

Campden tablets (potassium metabisulfite) are used to sanitize must before pitching yeast. They release sulfur dioxide, which kills wild yeast and bacteria. The problem is that SO2 doesn’t distinguish between wild yeast and the commercial yeast you want to add. If you pitch your wine yeast too soon after adding Campden tablets, the sulfite is still active and kills the new yeast before fermentation can establish.

The standard waiting period is 24 hours minimum — 48 hours is safer, especially in warmer must where SO2 dissipates faster. Skip that window, and your yeast lands in a chemically hostile environment.

How to Fix It

If you suspect this is the cause, wait the full 48 hours from your last Campden addition before repitching. Stir the must vigorously once or twice during that period to help drive off residual SO2. Then pitch a fresh packet of EC-1118 that has been properly rehydrated. One Campden tablet per gallon is the correct dose for sanitization — using more doesn’t sanitize better, it just makes the problem worse.

How to Restart a Stuck Fermentation

Once you’ve identified the cause using the sections above, here’s the step-by-step restart protocol that works across most stuck fermentation scenarios.

1. Take a hydrometer reading and record your current SG. If it’s below 1.000, stop — fermentation is done, not stuck.
2. Check and correct temperature. Get the must to 68°F–72°F and hold it there for 24 hours before doing anything else. A heat mat helps maintain consistency.
3. Degas gently. Stir the wine with a sanitized spoon to release dissolved CO2. This also oxygenates the must slightly, which helps yeast restart.
4. Add yeast energizer at 1/2 teaspoon per gallon. Stir it in well. Wait 30 minutes.
5. Prepare a yeast starter. Rehydrate one packet of Lalvin EC-1118 in 104°F water with a pinch of Go-Ferm. Let it sit 20 minutes until you see activity (foaming or swelling).
6. Acclimatize the starter. Add a small amount of your stuck wine to the starter — about two tablespoons — every ten minutes for 30 minutes. This bridges the temperature and alcohol gap so the yeast aren’t shocked when pitched.
7. Pitch the starter into your fermenter and stir gently.
8. Check SG after 48 hours. If it drops even a few points, the restart worked. Continue monitoring every 24 hours until you reach your target gravity.

If the fermentation still doesn’t restart after 72 hours at proper temperature with a fresh yeast pitch and nutrient addition, go back and reconsider whether you’re dealing with a high-sugar lock situation (Cause 4) or a Campden residue issue that needs more time to off-gas before a second repitch attempt.

Stuck fermentations feel more alarming than they usually are. Most of them have simple, fixable causes. The difference between someone who loses a batch and someone who salvages it is usually just the discipline to diagnose before acting — take the hydrometer reading, work through the causes in order, and resist the urge to throw everything at the problem at once.