How To Stop Homebrew Fermentation Explosions

Have you ever checked on your homebrew to find liquid spilled across the floor and broken containers? If so, you’ve likely encountered a homebrew fermentation explosion. Fortunately, there are several ways to stop fermenting homebrews from exploding.

There are several ways to stop homebrew fermentation explosions. Using high-quality bottles equipped with airlocks, keeping your fermenting homebrew at room temperature, and taking the time to sanitize equipment beforehand are excellent ways to avoid explosions.

Continue reading to learn more about how to prevent homebrew fermentation explosions.

1. Use High-Quality Bottles and Fermentation Buckets

It is crucial to keep your homebrew from exploding during the height of the fermentation process (aka while it’s still in the carboy or fermentation bucket).

You’ll want to ferment your homebrew in thick glass carboys or plastic fermentation buckets

The right option depends on your brew yield, with carboys generally being the better choice for smaller brews and buckets being an excellent resource for more extensive homebrew operations.

And to keep the pressure inside these containers stable, you’ll need to apply an airlock and seal to each container’s lid or opening. This device will allow gases to escape while keeping outside air and bacteria out.

An airlock will also help you keep track of your brew’s fermentation process! 

When fermenting a yeast-based beverage, it releases gases as a byproduct. These gases will form tiny bubbles in an airlock, indicating that the yeast is still converting sugars into alcohol.

When the bubbles cease, it’s an excellent indicator that the fermentation process is complete and that you can move on to bottling. Of course, using suitable bottles and bottling equipment is just as vital to preventing explosions.

Avoiding Explosions When Bottling Fermenting Homebrew

Inferior bottles won’t stand up to the extreme pressures building up in the beer. 

So, invest in premium-quality bottles for your homebrew. The best bottles should comprise thick, dark glass. Generally, the thicker the glass, the more pressure the container can withstand.

You’ll also want to use the recommended bottles for beer conditioning. They will be stronger and more resilient to withstand extreme pressures

Also, ensure the bottle caps you’ve chosen are of premium quality, and invest in a bottle capper for easy application. Doing so will provide a tight seal to keep pressurization stable.

Remember, bottle caps and cappers are integral to your homebrewing equipment collection. You should ensure they are cleaned and sanitized to avoid contaminating your homebrew.

Of course, knowing how much to fill your bottles (and your fermentation containers) is also essential to avoiding unwanted fermentation explosions.

2. Don’t Overfill Your Brewing Containers and Bottles

The fermentation process generates gas, namely carbon dioxide (CO2). When trapped inside a container, this gas creates pressure.

If you overfill your fermentation containers or bottles, the pressure of the gas can exceed the strength and integrity of the container, resulting in explosions. For that reason, leaving space at the top of your bottles and fermenting containers is essential.

Essentially, you’ll want to allow some headspace for the CO2 to express itself. As a rule of thumb, an inch of headspace is enough.

Of course, most beer recipes specify the ideal amount of headspace based on yield and container size, so be sure to refer to your chosen recipe for a more exact measurement.

3. Keep Fermenting Beverages Away From Heat

Temperature is one of the most impactful factors when fermenting homebrew beers. That’s because yeast requires a specific temperature range to activate. 

If your brew is too cold, the yeast won’t come alive, resulting in a lack of alcohol production. But if it’s too hot, the yeast can die, and your homebrew can sour, which is equally disastrous!

But heat and sunlight exposure don’t only affect your brew’s ability to generate alcohol. These elements can also cause homebrew explosions, especially during the fermentation process.

Have you ever noticed that most beer bottles are a dark amber color? This color isn’t accidental.

In the form of ultraviolet (UV) light, sunlight can kill yeast cells. This type of light also generates heat and energy, two forces that significantly impact the molecular structure of liquids and gases.

Generally, gas molecules pull tightly together when temperatures drop. This pulling together is why your car or bike tires might get slightly flat during a cold snap. The air inside them has condensed!

But the opposite effect happens when you expose gases to high temperatures. They move apart, generating pressure if trapped inside an airtight container.

Because the homebrew fermentation process produces CO2, keeping your fermenting beverages at room temperature and out of sunlight is crucial. You’ll also want to store bottled homemade beers in cool locations like refrigerators or basement cellars. 

Of course, if you live in a hotter region, you may experience more bottle explosions if you don’t have colder storage options. Still, if possible, avoid storing your homemade beer in an area where the temperature fluctuates

4. Don’t Use Too Much Priming Sugar in Your Homebrew

You can’t transform yeast into alcohol without the help of sugar, and most homebrews utilize priming sugars to get the job done. But too much priming sugar can be a terrible thing.

One of the primary causes of beer bottle explosions (during secondary fermentation) is adding too much priming sugar. 

The process works as such—the yeast in your homebrew feeds on the priming sugar, releasing CO2 and producing alcohol. The more sugar available to the yeast, the more byproducts it can generate.

So, if you add too much sugar to your mixture, excess CO2 production—results in over-carbonation. Even with an airlock, this abundance of gas can result in messy explosions.

Fortunately, many beer recipes feature a specific measurement or ratio of priming sugars for each volume of beer before conditioning. Paying close attention to your chosen recipe and using a scale to measure precisely can help you avoid adding excess sugar.

But ensuring you add just the right amount of sugar is vital to avoiding homebrew fermentation explosions.

Mix the Sugar Into the Brew

Failing to mix the priming sugar into your liquid mixture can lead to uneven distribution of the sugar, especially when it comes time to bottle.

The unprocessed sugar slides out of your carboy or fermentation bucket and reacts with the yeast in the brew. This results in secondary fermentation—and the gases generated during this process can quickly shatter bottled beers. 

In this situation, it’s not uncommon for some beers to explode in their bottles while the rest remain flat with little carbonation. 

Be Careful When Adding Sugar During Secondary Fermentation

Exceeding the right amount of priming sugar when bottle conditioning is the quickest route to bottle explosions during fermentation. Adding priming sugar to homebrews in secondary fermentation may not be a simple process for some homebrewers. 

There are many specifics involved, and one wrong move can lead to undesirable results beyond bottle explosions which is a worst-case scenario. 

Different sugar types have specific weights and volumes to include in your beer according to the size of your gallons. Also, you have to determine the temperature of your beer and a few other parameters to determine how much sugar you can add. 

You can use this priming sugar complete guide in your secondary fermentation. The sugar guide will also help you mix the priming sugar properly to ensure even distribution across all bottles. By following the correct ratios, you can eliminate sugar as the cause of any homebrew explosions!

5. Be Patient With Primary Fermentation 

Waiting for your yeasty homemade brew to finish fermenting into a tasty beverage can be challenging, even for the most patient homebrewers. 

However, bottling your brew too soon can leave you with shattered bottles and soggy fridge shelves. Therefore, you’ll need to practice patience while your homebrew completes the primary fermentation process.

After all, fermenting the perfect homebrew is a natural process, and you should enjoy each aspect of the alchemy of home fermentation. 

Why Bottling Too Early Can Result in Explosions

One of the major byproducts of the fermentation process is CO2. While your brew is still in its carboy or bucket, this gas can escape via the airlock! 

But bottling a beer when the primary fermentation isn’t over is a recipe for a bottle bomb disaster. 

Since a capped bottle is airtight, the CO2 released via fermentation won’t have ample room to move about freely or escape. As a result, it will build up inside the bottle, increasing the internal pressure and eventually shattering the container or popping the cap. 

So if you’re impatient in the primary fermentation stage, you not only risk having bottle explosions (which are dangerous due to shattered glass), but your beers can also end up uncapping themselves, resulting in stale, unsafe drinks. 

Time the Primary Fermentation

Primary fermentation can last between 48 and 72 hours, depending on the beer type, ingredients, and recipes. To be sure your beer’s primary fermentation is complete, check its specific gravity using a hydrometer.

Check after the first 36 or 48 hours and if it’s not yet there but you notice some changes in the figures, bottle it up and resume waiting. If you don’t have a hydrometer, I suggest you invest in one since it’s cheaper than most of your brewing tools and will serve you for a long time.  

Listen, I battled with feelings of impatience when I first started homebrewing. The result? More than a few shattered bottles and a very sticky pantry floor.

I’m sure many new homebrewers are going through the same issue. But no matter how eager you are to transform your homebrew into bottled goodness, try to give it a minimum of one week to ferment correctly.

Observe the Airlock Often

Your collection of homebrew equipment can quickly add up, resulting in a laboratory’s worth of items that can be challenging to keep track of (and keep clean). 

If you’d prefer to go without a hydrometer, you can use your carboy for fermenting bucket’s airlock as a handy fermentation indicator. 

Spending a few minutes observing the airlock each day is all you need to keep an eye on the primary fermentation process. If you see bubbles, leave that brew alone for a while longer!

But if the mixture is bubble-free for a day or more, you’re likely in the clear for bottling, especially if you’ve followed the above steps (mixing the sugar properly, keeping the liquid away from sunlight, etc.).

6. Sanitize Your Equipment 

Brewing beer at home requires attention to every detail, beginning with your brewing equipment. A piece of dirty equipment will lead to the beer’s infection, which can cause bottle explosions. 

This issue happens when bacteria from unclean equipment infect the beer. Thus, it leads to agitations or a series of other chemical reactions that increases the pressure of the beer in the bottle. 

Infection doesn’t happen only when you use dirty beer bottles for conditioning. It can happen at any stage of homebrewing, so you should be more hygienic with your equipment and the entire process. 

Sanitize and sterilize all your homebrew equipment to ensure you don’t introduce bacteria into your wort. 

When your beer gets infected, it’s no longer safe for drinking. Hence, pay attention to every item in contact with your wort. 

Also, be careful of all equipment that plays even the most minor role in homebrewing. Ensure all equipment goes through washing, sanitizing, and cleaning before use. 

Conclusion 

Explosions during fermentation are common occurrences in homebrewing and one of the challenges many homebrewers face. It’s due to a few mistakes in the processes leading to the bottling, which you can correct to avoid future explosions. 

To ensure beer bottle explosions never happen in the future, take note of the following: 

  • Give the beer enough time to ferment 
  • Sanitize all your equipment to avoid bacterial build-up that leads to explosions 
  • Use the right amount of priming sugar during the bottling stage   
  • Use the recommended bottles for secondary fermentation, and store them in a cold and dark place.

About HomeBrewAdvice

Hello, my name is Simon. Together with a group of writers I write about brewing beer and making wine. We all share a passion for the great things in life, such as making stuff from scratch.

The business of HomeBrewAdvice is to bring you great information, stories and product reviews from brewing at home, and making wine


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