You’ve just pitched your wort, put the lid on your fermenter, got your airlock in place, and now you step back and wonder how long it’s going to be until bubbles start to form in your homebrew.
If you’re like me, you’ll get a rush when you see those tell-tale signs that fermentation has started and that you’re one step closer to beer. But how soon should you expect that proud ‘parent’ feeling?
On average, signs of fermentation become visible 6 to 48 hours after yeast is added to the wort. Variables affecting the onset of fermentation include temperature, yeast type and viability, oxygen & nutrient levels in the wort, and airtightness of fermentation vessel.
Here’s the thing: homebrewing is chemistry with an extremely tasty outcome.
As with any chemistry, you’ve got to control the variables, or you’ll end up making off-tasting beer or even something that’s not quite beer because your fermentation process never took off.
There’s a trick to getting it right, and I’m here to share the fruits of my experience with you so it doesn’t go wrong.
How long does it take to ferment a beer?
Several variables are involved, and I go into more detail about how long to leave a beer fermenting here.
What factors influence healthy fermentation?
Four main factors go into achieving a robust fermentation process.
Yeast – The yeast needs to be viable and in an environment it can grow in.
Temperature – This is key. Too hot or too cold will lead to worthless yeast.
Aeration – Not to be confused with oxidation. Yeast needs air to properly function at the beginning.
Nutrients – Yeast also needs food. Fermentation just won’t happen without it.
Those are the factors. So how do you ensure they’re ideal?
Tips to get a healthy fermentation
Use yeast that’s not too old
Checking the expiration label on the package is the obvious way to stay on top of this, but plenty of brewers have been known to use yeast that’s “expired” according to its packaging and produce perfect beer. In truth, yeast dies when it dies, not when the package tells it to.
Thankfully, there are some ways to tell if beer yeast is dead. So please check out my article for more details.
Make sure the wort has been chilled to the right temperature
This allows the yeast to survive and do their job. 68-72 degrees F (20-22 C) is the optimal range for ale yeasts, while lager yeasts need a notably cooler environment: 45-57 degrees F (7-14 C). Pitching at higher temperatures than this can lead to a yeast massacre.
Manage your temperature to be in the perfect range for the yeast to ferment the beer
There are a lot of ways to do this, ranging from specialized equipment to DIY approaches. They’ve all got their pros and cons. Portable air conditioners are one way to keep your beer cool, while heating belts can warm things up if temps start dipping too low. I personally have gone with a regular chest freezer, aquarium heater, and a temperature control unit (Ink Bird ITC-308 on Amazon).
Aerate the wort well
Now, granted, we always hear brewers talking about how oxygen in beer is bad news. This is true except for one time in the beer-making process: wort needs good aeration after you’ve boiled and cooled it to fermentation temp but before you’ve pitched it with yeast.
If you’re using a bucket for fermentation, one way to aerate is to sanitize a good, old-fashioned steel kitchen whisk and whip the wort until you’ve got about two inches of foam on the top. If using a glass carboy, you can rock it carefully back and forth so that the wort sloshes around inside.
Alternatively (and this one works for either bucket or carboy), you can always get some good aeration going in your wort at the point when you transfer your boiled wort from kettle to fermentation vessel.
Transferring, whether you do it with tubing or with a wire mesh strainer, provides plenty of opportunity for splashing. Splashing is one of the easiest and cheapest ways to get some oxygen in your wort.
Make sure the original gravity is close to the predicted gravity
This essentially means your wort has plenty of nutrients for the yeast to feed on. To get a read on this, before fermenting your wort, you can use a hydrometer or refractometer to measure how much sugar has been dissolved in the water.
If you find that your original gravity is too low, dry malt extract can be used as a supplement. If your original gravity happens to be too high—not particularly common, but also not unheard of—the wort can be diluted with water.
What if you haven’t seen bubbles after 24 hours?
If bubbles haven’t started coming up in your airlock (or blow off tube) after twenty-four hours, you might be tempted to think it’s all over as far as this batch is concerned. Well, that’s not necessarily true. Sometimes it takes a while for fermentation to start. There are a number of possible reasons for that.
One reason may be that you pitched at a bit warmer temperature than ideal, and now your yeast is shocked. Shocked yeast takes longer to come around and get moving, just like people in the same situation.
If you didn’t pitch your yeast at a problematic temperature but are still not seeing bubbles, try checking the temperature of your brewery. If it’s too warm or too cool, correct the temp.
Here is a good time for me to mention that a fermentation chamber might just be the thing for you if you find this happening a lot. A fermentation chamber is a box—one example being my chest freezer—that holds your beer and helps keep your brewing temperatures at the perfect levels.
If you want to know more about why a fermentation chamber improves the quality of your brew, or how to build one, check out my article on the topic here.
Just one little tip if you are thinking of buying a fridge or chest freezer to transform into a fermentation chamber, always go bigger than you need. It’s more than likely that you’ll need to upgrade at some point, I certainly did!
What to do if your beer isn’t bubbling after days?
My advice for this is generally the same as above. It’s all about the yeast. So first, take a gravity reading to see if the yeast is fermenting the beer or not. Make sure all the environmental variables are good (temperature, etc.)
You can add more yeast, preferably in a yeast starter that will get it blooming before you add it. This ensures the yeast is fully developed before going into the wort. This is especially important if you took a risk and used old yeast in your original pitching attempt. It’s probably slipped off its mortal coil.
Why is my airlock not bubbling?
If you’re not seeing bubbles come up in your airlock, it may just mean that fermentation has slowed. This is especially true when it was quite active during the initial growth phase of fermentation. In this case, check the specific gravity of the beer and monitor it for change over a couple of days.
It’s also possible that your fermenter isn’t airtight. In this case, with the C02 trickling out through your loose lid, your airlock won’t bubble. This isn’t a big deal in and of itself but remember: if your fermenter isn’t airtight, there’s a risk of oxidation. Unless you want your beer to taste of wet cardboard, you don’t want this!
My beer stopped bubbling after a couple of days!
If your beer bubbled for a few days and then stopped, it might be a cause for celebration (fermentation is over, and your beer is ready!) If your wort was on the higher side of acceptable temperatures, it’s possible you’ve completed the active part of fermentation this soon.
So what to do with this early-bird beer? Most brewers will say to leave the beer a while longer before racking it to bottles or a keg (or starting secondary fermentation), and then, to really be safe and get some clear answers, get a gravity reading with a hydrometer after seven to ten days.
Then, two days later, take another reading. If the two readings are the same, it’s safe to say the beer is ready for secondary fermentation (if you’re taking that step) or bottling/kegging.
On the other hand, a beer that stopped bubbling could indicate stuck fermentation. This means the yeast has become dormant before consuming all of the available sugars in your wort. In other words, the beer hasn’t reached its expected final gravity.
As with most things related to homebrewing, there are a few possible reasons this could be happening. There are also a few tried-and-true tricks for fixing them. If you’re stuck (see what I did, there?) in this situation, I’ve already written the perfect article for you here.