10 Reasons Your Home Brew Fermentation May Have Stopped - Checklist
Sometimes you make a wine, beer, cider or mead and it starts fermenting beautifully. Then... it stops. There could be at least 10 reasons why your fermentation may have stopped, and I've put them together here as a checklist. If your fermentation hasn't yet started, you might find my post 10 Reasons Your Wine Fermentation Won't Start helpful.
It can be frustrating when you think everything is going along well, then something happens and, suddenly, it isn't. Fermentation starting and then stopping tends to be more common when you make drinks from scratch rather than from kits, but that is by no means always the case.
Incidentally, if you are making a kit, then follow the instructions provided to the letter rather than going off into the realms of what I cover here. The only reasons a kit starts fermenting and then doesn't continue is either because it has fermented out extremely quickly, or the area in which your bucket or demijohn are located is suddenly too cold.
You may have Googled and found this post, or you've contacted us asking for advice and I've sent you here. So on with the checklist...
Home Brew Fermentation Has Stopped - Checklist
1. If you added Campden Tablets to your wine, did you leave it for 24 hours before adding the yeast?
Your recipe may have included Campden Tablets in the ingredients. It should also have said you once you've added them, you should leave the mix for a further 24 hours before adding yeast.
Campden Tablets are designed to kill any bacteria and/or yeasts in your fruit, vegetables, or whatever else you are using. This is because unknown bacteria and spores can spoil your wine. When you use Campden tablets you are clearing out all those things to enable your fermentation to be predictable, since the only yeast in your wine will be the one you added.
Campden tablets kill everything, including yeast. Hence you must leave the brew for at least 24 hours after adding campden tablets, before adding your yeast. That means the Campden has had time to do its job, leaving none remaining by the time you add the yeast.
If you didn't leave the Campden Tablets in your wine for long enough for those gases to disappear before adding your yeast, you may have partially killed the yeast you added. This can cause your fermentation to start very slowly and be quite sluggish, only to stop at some point because there isn't enough live yeast left to continue fermenting.
Solution: add more yeast, though be careful if there is likely to be a lot of sediment as a result of doing this (see point 10).
2. If you added Campden Tablets to your wine, did you leave the vessel open to the air for 24 hours before you added your yeast?
If you added Campden Tablets to the mix, your recipe should have said to leave the vessel open to the air for 24 hours.
When you add sulphites like Campden Tablets, they start working away killing bacteria and moulds. They then dissipate into the air in the form of a gas. You are usually advised to loosely cover the vessel with a clean tea towel/similar for that first 24 hours. This prevents fruit flies and dust getting in whilst allowing those gases to get out.
If you seal the unit when you add the Campden Tablets, the gases can't get out. So when you go on to add yeast 24 hours later, some gases could still be present. Those gases will either kill the yeast completely or partially kill it, which can lead to a very slow start to your fermentation. Once that small amount of remaining yeast has finished, the fermentation will stop.
Solution: add more yeast, though be careful if there is likely to be a lot of sediment as a result of doing this (see point 10).
3. Are conditions warm enough for fermentation to continue?
There are times of year which can make home brewing a little less predictable. In summer it tends to be warm. In winter it tends to be cold. However Spring and Autumn can be a mix of both.
32 degrees today. Bonkers. The mango and hedgerow meads were fermenting so quickly, they were threatening to overflow. Relocated to the cool cellar (usually too cold for fermentation). Perfect. Might move down there myself... #brewster #mead #meadmaking #meadmaker #homebrew
You may have started your wine in early autumn, and suddenly the temperature has dropped dramatically - particularly at night. If your demijohn or bucket is in a cold place and the contents get particularly cold, they may struggle to get warm enough to get the yeast going again.
Check whether your yeast packaging has temperature guidance on it. Many give ranges and/or ideal temperatures, and these can vary. For example:
Lalvin All Purpose Yeast K1-V1116 - 10-35°C (50-95°F)
Lalvin Sparkling Wine & Champagne Yeast EC-1118 - 10-30°C (50-86°F)
Gervin GV9 White Wine Yeast - ferments down to 10°C.
If your yeast doesn't give any temperature guidance, most yeasts should definitely work between a range of 21-24°C. And anything under 10°C means the yeast will struggle to continue fermenting, even if it got going successfully. Most issues with fermentation are temperature related, and increasing the temperature is often enough to get it going again.
Solution: move your vessel nearer to a heat source, such as a radiator or woodburner. Don't move it too close, because extreme heat can kill your yeast. Once it re-starts, you can move it somewhere more convenient. Keep an eye on it, in case it stops again. If it does, you'll know your chosen position is definitely too cold.
4. Has your vessel got cold and the yeast has sunk to the bottom?
We advise customers against continuously opening their brewing vessel once yeast has been added, because of the contamination risk. But if your yeast got cold and stopped, it may need a little encouragement. Sometimes just getting yeast back in suspension can get it going again.
Solution: swirl the demijohn around so the yeast gets mixed in again. If the brew is in a bucket, lift the lid and stir the mix with a sterilised plastic spoon, then quickly replace the lid.
5. Is air suddenly escaping from the vessel some other way?
Generally you know your fermentation is going because air is moving through the airlock. If it has now stopped, did something change? Did you move it and, for example, knock the demijohn a little when you did? Did the bucket lid get lifted? Air may be escaping some other way.
Take a good look at the surface of the brew. If it's in a demijohn, can you see little particles moving around? If it's in a bucket, can you see small bubbles forming on the surface?
If the fermentation was slow to begin with, it may be that it has now stopped because it never got going properly in the first place. Or it could be that the lid of your bucket is not fitted securely, or the bung in your demijohn is allowing air to escape So it is still fermenting, you just can't see it because the air isn't escaping throught the airlock.
Alternatively, you may have a huge gap in the top of, say, a bucket that you're fermenting in, because you're trying to ferment in a vessel far bigger than the quantity of juice you have. What you sometimes find in that situation is that the gap of air is so huge between the surface of the liquid and the lid, the pressure never builds enough for air to escape. You also risk mould forming if that is the case, because the air never becomes (in effect) a sterile space.
Solution: if you are fermenting in a bucket, make sure the lid is securely fastened and the airlock is firmly in the grommet so no air is escaping. If you are fermenting in a demijohn, ensure the airlock is still firmly pushed into the bung and the bung is firmly in the neck of the demijohn. If you have too little liquid for the vessel you are fermenting in and there is a big gap on the surface of the liquid before the neck of the demijohn/lid of the bucket, either transfer to smaller vessel(s) and/or top up with grape juice concentrate to reduce the gap.
6. Did you fit an airlock too quickly?
If you are making a recipe from scratch and have moved your brew from one vessel to another and then fermentation has stopped, you may have moved it too soon.
Most recipes advise you to mix up the fruit, vegetables, honey and whatever, add the yeast and leave the brew in the bucket covered with a loose fitting lid or tea towel. You then leave it like this for anything between 1 and 10 days depending on the recipe, stirring daily with a sterilised paddle or spoon whilst primary fermentation takes place, which can be quite vigorous. This also means you can avoid an overflowing demijohn.
Then things calm down and it moves into secondary fermentation. You then seal the vessel and add an airlock.
You need your yeast to multiply, and yeast needs air to do that. So, whilst it sounds a bit mad to say 'it's so important to sterilise everything' whilst at the same time saying 'expose the liquid to the air', that really is what you need to do.
Once the yeast has reproduced itself over time, it will then start working on turning the sugar in to alcohol. That needs to happen in a sealed vessel with an airlock. However if you seal and add an airlock before the yeast has got going properly, fermentation may never really get going at all.
Did your fermentation start but then, when you moved it into a sealed vessel with an airlock it stopped? This may be the reason.
Solution: open the lid again, or put the wine back into a vessel with a wide neck (or the original bucket). Cover with a tea towel/cheese cloth or similar, with a rubber band around it as this will be very appealing to fruit flies at this point. Wait until you're certain the fermentation is working before you fit the airlock again.
7. Were there yeast nutrients in your recipe?
Most recipes have either a home brewing yeast nutrient in them, or at least some fruit that acts as a yeast nutrient (such as raisins). Did your original recipe have yeast nutrients in it?
If not, the yeast may have not had enough to feed on to keep going. Go back and add either a home brewing yeast nutrient to your vessel or a few raisins. You could also consider adding a Re-Start Yeast (next point on the checklist).
8. Will it simply not start whatever you do, and you suspect your yeast is no longer active?
There are a number of Restart Yeasts available. Restart is a vigorous strain of yeast designed to help complete fermentations that are sluggish, or have completely stopped. They can kick start fermentation quickly. Champagne yeasts such as Lalvin EC-1118 are renowned for their ability to do the same thing.
Solution: add a ReStart yeast or Lalvin EC-1118 yeast according to the packet instructions. Be careful if there is likely to be a lot of sediment as a result of doing this (see point 10).
9. Were there preservatives in any of the ingredients you added?
Many shop bought juices contain preservatives which are, by definition, designed to kill yeast. If you thought you'd just add a little flavouring in the early stages, any preservatives present may have killed your yeast.
Solution: this is a tough one. If the preservatives are in there, they are not going anywhere and the party may be over. I hate giving up, so would add some Re-Start (above) in the hope of getting it going. But you may have to pour it down the sink and start again.
10. Is it time to rack off the sediment and start again?
If there are any issues with your yeast at all, I have suggested above that you add more and/or Restart Yeast. In theory you cannot add too much yeast to a fermentation. If there is too much yeast for the sugar present, the unused yeast will simply sink to the bottom along with other sediment and do nothing.
But having a lot of yeast in your sediment isn't ideal. If your wine sits on it for months, it could affect the taste and/or and make the wine more difficult to clear. And occasionally if live yeast has sunk to the bottom and sat there dormant, it might start fermenting again later. This can lead to exploding bottles which is definitely what you don't want!
Solution: if you've concluded there's probably a yeast issue but adding more is going to mean lots of sediment, you could rack the wine out of the vessel into another sterile vessel leaving the old yeasty sediment behind. Then add fresh yeast and, in effect, start again. More about Racking here.
Bonus Point 11: Might the Fermentation have stopped because it has finished!
I know I now sound like Captain Obvious, but stranger things have happened. Obviously if fermentation started 2 days ago, it hasn't finished. But if has been going for a while, is it possible it has completed fermentation? A hydrometer will tell you that.
Starting Gravity for a typical wine would be 1.070 to 1.090. Finish Gravity would be 0.990 (for dry wines) to 1.005 (for sweet wines). Worth a check?
It may be that you're reading this simply out of interest before you begin to make your wine, beer, mead or cider. However if you are reading it because you have a fermentation that won't start, we hope you find it helpful and you get your brew going again very soon!