Fermentation is the essential part of brewing and it’s important to ensure that your brew is fully fermented within the right conditions. If you screw at this stage, nothing will save your homebrew and you’ll have to start all over again.
So, how do you know if your homebrew is fermenting?
You can tell that your homebrew is fermenting when you spot the first bubbles coming out of the airlock. It means the yeast is producing Co2 which indicates the fermentation has kicked in. You’ll also smell the fumes the yeast produces and these signals will slow down as fermentation completes.
However, although this is a sign the fermentation has kicked in, it’s not always enough to see bubbles and smell the fumes to know that fermentation is going right and to know when it’s complete.
In this article, I’ll explain important facts about fermentation you must know to ensure your homebrew will finish properly. Fermentation can sometimes be sneaky, and depending on a recipe it may fool you, but worry not, I have experienced all of its sneaky tactics on my brews already.
When should fermentation start?
If you are worried that your beer is not fermenting after 12 hours or so, do not worry, you should give it at least 24 hours before it will start to kick in. Moreover, it can sometimes take another 12 to 24 hours to see the first bubbles because the Co2 needs to accumulate at the top of the fermenter before it will have to pass through the airlock.
So, you should see your first bubbles within 48 hours, it can be sooner or later but within this time frame.
There are a few factors that will determine when you’ll spot the signs of fermentation and one of them can even be the size of a fermenter and how much wort is in it.
However, you should only focus on ensuring a healthy environment for your yeast to reproduce its colonies.
What to do if fermentation does not start
If your homebrew didn’t start to ferment within 48 hours, you’ll need to analyze what went wrong before you can continue and I will help you with this.
Even if the homebrew fermentation didn’t kick in due to mistakes, it doesn’t mean the end or that you’ll have to trash your brew.
1. Check the temperature
Every yeast kind is different and enjoys a different temperature range and it’s important to keep the temperature stable until fermentation completes. Check the description on the back of the yeast package and see what temperature is recommended.
You need to ferment within that range, or yeast can go dormant from the cold or die due to heat exposure.
In case the temperature is too cold for yeast to reproduce all you have to do is warm up the fermenter and give it some time.
If you ferment way too long at a warm temperature, your yeast is probably dead and the best thing you can do is to lower the temperature and hope there are some yeast cell survivors.
However, it almost certainly won’t be enough yeast cells for a proper fermentation if the temperature is too warm even for only 6 hours, so you’ll have to pitch new yeast.
To know whether it was too warm for it or not, you’ll need to see at what range can your type of yeast survive, because keeping it at its highest range for a few hours may not be a big deal, but may become after 6+ hours, or if you pitched it at an even higher temperature (over its limit) it may die after minutes.
2. Give it more time
You can’t know what’s going on in the mind of the yeast, so perhaps it decided to start to slowly kick in.
Yeast can act weirdly from time to time, so if all conditions are right and you pitched it at the right temperature, just give it another day.
You don’t have to worry that the beer will go bad if you keep it in the fermenter even if fermentation is complete, it’s always good to keep the beer in the primary fermenter for extra time after fermentation is done.
I have brewed both the beer and the mead and I always had fermentation within 48 hours no matter what, but as I said, the yeast can surprise us!
3. Supply the yeast with nutrients
When yeast gets weak you can feed it with yeast nutrients such as phosphate, amino acids, dead yeast cells (sounds cannibalistic because it is), Zinc, and so on. This will help the yeast regenerate and promote the growth of its colonies. However, this is something not often necessary with beers (except in some recipes), but rather with ciders and mead.
These nutrients are needed when the recipe doesn’t contain rich nutrients the yeast can use, but rather simple sugars alone. Beer recipes contain malts that are rich in calcium, magnesium, potassium, and so on, but mead or ciders only contain sugars.
Therefore, check the recipe you used and see if you need yeast nutrients.
This is rarely needed for a majority of beer recipes, but as I said, in cases with mead and similar brews it’s desired and can be the factor that will help start the fermentation.
High adjunction or ABV beer recipes can also benefit from this, so in some instances, this can be a good method even for brewing beer.
On the other hand, If the yeast is dead, this won’t resurrect it.
If none of these helped and you are absolutely certain your yeast is dead, you’ll need to buy new yeast and pitch it once again. This time ensure you do not commit the same mistakes and it will be alright.
How to tell when beer fermentation is complete?
The hydrometer method is the best and most accurate way to determine whether the fermentation is complete or needs more time.
By taking the gravity readings you can know what’s going on with the fermentation because alcohol is lighter than water and sugars. When yeast eats sugars and produces them into alcohol, you can clearly see the science behind hydrometer readings.
It’s important to complete the fermentation because it won’t only affect the ABV, taste, and texture of your brew, but can also cause bottle bombs.
How to tell when fermentation is done with a hydrometer?
To check the fermentation status with a hydrometer you’ll need to take at least two readings with either 3 or 7 days in between.
If you are brewing a regular or low-ABV beer that ferments no longer than 10 days on average, you can take one reading with a hydrometer and a second one 3 days later and compare them.
If you brew a high ABV beer or mead you’ll need to take two readings 7 days apart because the noticeable difference will be better observed with a greater time period as high ABV brews take longer to ferment.
Once you have two readings, compare them and see if has anything changed, If the gravity is identical on both readings you are safe to conclude that the fermentation is done.
If you notice even the 0.01 difference in readings, you should wait another 3 or 7 days and take another sample.
The goal is to find identical readings on a comparison, so be patient!
How to tell when fermentation is done without a hydrometer?
Without a hydrometer, it is hard to be certain that fermentation is complete, but it’s not impossible.
If you brew beer you can generally guess when fermentation is complete based on the time you let it ferment if you brew recipes with the right ingredients that have been brewed by others thousands of times.
Usually, standard ABV beers will take no longer than 10 days to finish fermentation, and if you want to be extra sure you can give it another few days to a week.
High-ABV beers can ferment for over a month and are less predictable than lower-ABV beers, so it will be harder to say when they are done.
Anyway, if you know the recipe, just let it ferment under the right conditions for a given time and give it another week or so to be completely sure.
It’s always better to let the brew sit in the fermenter for a bit longer than to cut the fermentation process.
Once the fermentation is complete, it means the sugar has been completely eaten by the yeast, or yeast can no longer work within a high-alcohol environment.
In any case, yeast will go inactive and the brew won’t get spoiled if it continues to sit in the fermenter if it’s sealed and out of sunlight.
How often should my homebrew bubble?
When you start fermenting your homebrew, bubbling is expected to be highly noticeable and regular but as fermentation completes it will get staler until it may stop bubbling completely at the end.
However, there are no strict rules on how much and how long should bubbles pass through an airlock, so depending on the fermentation it may be more aggressive or less.
Aggressive fermentation can overwhelm your airlock and even push some beer through it along with CO2.
As long as there are some bubbles during the fermentation, you don’t have to worry because the only concern would be if there were no bubbles at all as it would indicate the fermentation didn’t even begin.
Is fermentation done when bubbling stops?
Fermentation doesn’t have to be done when bubbling stops as yeast may still convert sugars into alcohol at a slower pace. On the other hand, fermentation may also be complete but bubbles will still pass through the airlock for days because there’s still CO2 trapped at the top.
Bubbles are simply the Co2 that escapes and it’s impossible to know the state of fermentation based on it besides some assumptions about the pace of fermentation, so don’t worry about it.
Why is my homebrew not bubbling?
If your homebrew isn’t bubbling it doesn’t necessarily mean that there’s something wrong with fermentation. However, if you didn’t spot any bubbling during the fermentation period it may mean that the fermentation didn’t even start.
Sometimes not many bubbles pass through the airlock if the pressure is not great enough and this can happen if you ferment small amounts of brew in a big fermenter.
To check whether there is any CO2 you can push the top of the fermenter with a finger and see whether the airlock bubbles or not.
However, this is only possible with plastic fermenters as you can’t apply such pressure on glass or steel fermenters.
Conclusion
Depending on the yeast strain used, fermentation can kick off within a couple of hours after pitching and sometimes it can take more than 24 hours.
It’s unusual for any yeast strain not to begin fermenting within 48 hours, and most yeast strains will begin to ferment already within 24 hours.
This has always been our experience with the majority of yeast strains we use, so be patient and ensure that you give your yeast enough time to kick off.
If for some reason yeast doesn’t begin to ferment after that, you should pitch new yeast as soon as possible and write down in the notebook anything suspicious that may have prevented yeast from activating.
The best way to monitor the fermentation process is by using a hydrometer, so you don’t have to make guesses but rather use science!