Do You Really Need an Airlock for Fermentation? (Try Without It)

Airlocks are basic equipment every homebrewer should have in their arsenal unless they are brave and decide not to use them which comes with benefits and potential dangers.

Airlock prevents oxygen from getting in while it simultaneously lets the CO2 escape and it is generally recommended that beginners use it. Although it’s recommended to use an airlock, there is more to say about this topic.

In this article, I will explain everything you need to know about when to use an airlock and when not to.

So, can you ferment without an airlock in the primary?

An airlock is recommended but is not necessarily for primary fermentation. It’s possible to ferment homebrew without an airlock with an open fermentation or by using a stainless steel keg with a pressure fermentation technique. Techniques that don’t rely on an airlock are not recommended for beginners because you need to be familiar with what’s going on.

For this reason, fermenting in an airtight fermenter with an airlock on is the safest method for homebrewers, especially for beginners.

Yet, if you want to know more about the possibilities of open fermentation, let me explain how it works and why it’s still a practice in some breweries in Europe.

What is open fermentation, and how does it work?

Open fermentation means fermenting a brew in a fermenter without an airtight seal. This is an old practice for beer brewing and you can find some breweries that use this practice, particularly in Germany, Belgium, and the UK.

The beer is placed in a big, long, and shallow vessel without a lid and left to ferment. This shape of a vessel used for fermenting allows the fumes to easily escape while it’s also easy for the krausen (yeast) to build at the top. This must be done in a safe room with no dust or nasty things floating in the air or otherwise, it could infect the beer.

For this reason, these breweries use special air conditioners to remove the impurities from the air and operate these processes in a closed environment to protect the beer.

The idea is that you don’t need an airlock if the CO2 and krausen build on top of the vessel because the CO2 is heavier than air and won’t let the air in.

This simplifies the process because the breweries only have to transfer the beer into airtight containers once the beer is done fermenting.

Additionally, open fermentation allowed better inspection because it’s easier to see what’s going on in the beer, and dry hopping or adding special ingredients is an easier task.

Open fermentation also allowed brewers to simply collect the yeast from the top and reuse it later and it’s said that due to the open fermenting vessels, the yeast produces better flavors which eventually means a better beer in certain beer styles.

This does make some sense because elevating the yeast from pressure which is caused in close systems means more freedom (and we know for a fact that the pressure affects yeast and can even kill it), and the “free-breathing” allows for fumes to escape easily without being trapped back into the beer.

How to ferment without an airlock at home?

So, do you like the idea behind open fermentation? If you do, you can do it at home but you have to be careful with what you are doing.

You see, I always use airlocks and air-tight fermenters because that’s how I started my homebrewing journey and it worked so well so far and they say don’t change the stuff that works.

However, I know people who did ferment openly, and their homebrew beer ended up great. They even claim that the beer ends up being better than the beer they brewed in a classic airtight fermenter with an airlock.

I can’t confirm whether the beer is better because I haven’t tried their beers and compared them but I know that open fermentation can be done at home.

This is how you ferment your beer at home in an open-fermentation style.

1. Only use ALE yeast (British ale yeasts are great for this purpose). Lager yeast should be avoided because it doesn’t form nice top layers and rather falls down.
2. Place your fermenter somewhere in a clean room that you won’t enter on a daily basis to ensure the risk of contamination is low.
3. Keep the lid on the fermenter just in case but don’t make it airtight by creating the seal (leave sides open so the air can pass). If you are brave and know that no chunks of dirt or bugs will end up in the beer you can fully remove the lid.
4. When you ferment at the right temperature and aerate wort the yeast should activate within a couple of hours and start building Co2 and Krausen at the top which will protect the beer.
5. In the first 3 days, you should use a sanitized spoon and remove most of the krausen formed at the top. After that, you can gently stir your beer to help the new krausen form, but do not touch the bottom of the fermenter. (If it’s a standard recipe that ferments for up to 7 days or so, otherwise increase it by a few days as the goal is to change the krausen during the most active days of fermentation). This will ensure the beer can breathe and release the fumes you don’t want in a beer while the new krausen will always form at the top. (You can store the krausen as it’s made from the yeast and re-use the yeast in the future).
6. As the fermentation completes, take the gravity readings, and when it’s done rack it with a siphon to an airtight container for secondary fermentation or bottle it straight from the primary.

As you can see the concept is that the krausen and Co2 protect the beer for the entire duration but as the fermentation becomes stale, you should no longer remove the krausen or disturb the beer because its protection gets weaker and weaker.

The beer is safe beneath the layers formed at the top, so rack it and it’s complete.

You can expect that the beer will end up with almost double the amount of esters which is desired for ales, but not for lagers. Therefore, if you like brewing ales you may really create something different that you haven’t yet tried, so give it a go!

What is pressure fermentation?

There is also an option to ferment in an airtight stainless steel keg which doesn’t use airlocks.

Pressure fermentation needs to be airtight and you must not use an airlock as the point it so create as much pressure from Co2 buildup as possible.

This is an interesting approach to fermenting but it’s something that needs extra gear like a keg and an anti-pressure valve, so it’s not a recommended technique for beginners.

Do you need an airlock for secondary fermentation? 

During secondary fermentation, there’s no active Co2 build-up if the fermentation is complete and thus it’s not necessary to have an airlock.

However, if there is still sugar left (meaning the fermentation wasn’t complete) the Co2 will continue building up and may build up pressure which can destroy the bucket.

Besides this, there will always be some CO2 trapped in a beer when you rack it, so it’s recommended to keep the airlock just in case.

So, I would keep the airlock on if I had it because it costs me nothing but you don’t necessarily need it. It’s more about safety and general advice because no one knows the specifics of your secondary fermenting bucket.

If it’s made of glass, or it is small and there is no layer between the beer and the top of the bucket and you don’t use the airlock it may cause issues, but otherwise, you’ll be good.

I always use a big plastic fermenter that can take some minimal Co2 pressure, so I don’t have to use the airlock, yet I still put it on because I have it by hand.

Can you remove the airlock during fermentation?

You can remove the airlock during fermentation if you need to replace it or if you plan to continue fermenting without it, but then the question is why would you begin with an airlock at all?

If you are not doing an open fermentation style, don’t remove the airlock during fermentation.

Another danger of removing an airlock in the midst of fermentation is that when you pull it out you can accidentally suck some nasty germs that were on the top of the lid around the hole which can contaminate the homebrew. This is why you should always sanitize everything whenever there’s a chance of something going wrong.

Refer to this article for more tips on what NOT TO DO during fermentation.

Conclusion- Does fermentation need to be airtight?

So, the fermentation doesn’t have to be airtight to create great-tasting homebrew but it’s a recommended technique because it’s the safest and works best in most instances. This is especially important for beginners who don’t need more room for mistakes.

There you go, stick to the recommended practices with an airlock if you want to be safe, but if you are a wandering soul go ahead and explore methods like open-fermenting or even pressure fermentation.