How to Use Airlock Bubbler

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An airlock bubbler is a device used by beer and winemakers to control the fermentation process. The airlock bubbler features a one-way valve that prevents the entry of oxygen while allowing the fermentation gases to be released into the atmosphere. Let’s talk about how to use an airlock bubbler.

How to Use Airlock Bubbler

There are two different types of water-filled airlock bubblers. The first one is the three-piece airlock bubbler, and the other one is the S-shaped air-lock bubbler. Both of these airlock designs work by forming a water trap that acts as a one-way valve. 

The carbon dioxide released pressurizes the fermenter during the fermentation process, and the CO2 bubbles push the water and escape. Keeping in mind that the pressure inside the fermenter is higher than the atmospheric pressure, the carbon IV oxide can escape, whereas the oxygen outside cannot enter the fermenter.

Also, the water prevents dust and bugs from entering the fermenter. At the end of the fermentation process, the space is full of carbon IV oxide, which helps equalize the pressure differences caused by temperature changes.

Fermenting homebrew beer with an airlock bubbler

Why Is an Airlock Bubbler Necessary?

During the fermentation process of yeast, some gases are released by the sugars in the liquid. The gases released are less dense than the sugars inside the liquid, so the internal pressure builds up. 

Therefore, it is essential to release this bubble of gas to the outside while preventing oxygen and other impurities from entering the fermenter. An airlock bubbler is specifically designed to allow gas bubbles to escape while protecting the liquid from external impurities. 

What Amount of Water Should You Put in an Airlock Bubbler?

The amount of water that you should put in an airlock bubbler depends on the type of bubbler. Here is how it should fill each type of airlock bubbler with water.

Filling an S-Shaped Airlock Bubbler 

These traditional S-shaped airlocks come with three bulbs on each side of the S-bend. When pressure builds up inside the fermenter, it pushes the water in the airlock towards one side, and finally, a bubble escapes.  

Once the gas bubble escapes, the water equalizers once again on both sides of this bend, and the process continues. If the airlock bubbler comes with three bulbs on each side of the S-bend, you should add sufficient water to ensure the bottom bulb is full.

However, if the airlock bubbler features one bulb on each side, you should only fill a third of it. Remember that filling the bulbs with the right amount of water is the first and most essential step in using an airlock bubbler.

Filling a 3-Piece Airlock Bubbler 

The 3-piece airlock bubbler features a central tube with a plastic cowl covering. When the pressure develops in the fermenter, it raises the cowl upwards, allowing a gas bubble to escape via the water. 

When filling this type of airlock bubbler with water, you should fill it to around halfway. The 3-piece airlock bubbler is less prone to blockage during active fermentation and easier to clean.

Here is a general way to use either type of these airlock bubblers:

  1. Fill the airlock bubbler halfway with water 
  2. Force the airlock gently into a cork or rubber bung
  3. Force the bung gently into the neck of the fermenter or a demijohn 
  4. Allow the fermentation process to take place, and you can occasionally check to ensure that water has not evaporated.
  5. In case you need to top up, top-up to the initial amount 

Anaerobic Respiration 

To have a better understanding of how fermentation works, what can go wrong and how you can know it’s complete, you’ll have to explore the biology of fermentation. Here is everything that you may need to know about anaerobic respiration.

Living organisms use oxygen to generate high-energy molecules from the sugars in food. These molecules are called ATP, and the process is called anaerobic respiration. Unlike plants, fish, and humans, yeast and bacteria can also manufacture these high-energy molecules using oxygen. 

Anaerobic Respiration in Fermentation 

When anaerobic respiration takes place, the byproducts depend on the involved organisms. In most cases, the byproduct is the high-energy molecule NADH, lactic acid, and alcohol, and CO2. Yeast turns the sugars into CO2, alcohol and high-energy, and NADH.

Yeast and bacteria do not require an atmosphere without air for anaerobic respiration to take place. However, the anaerobic environment helps eliminate any fungi or bacteria that might be competing to work on the sugars to generate a different byproduct other than alcohol and lactic acid.

Some of these bacteria are fickle and use aerobic respiration. It only resorts to using anaerobic respiration if there is no oxygen in the system. It, therefore, means for you to get fermentation from these kinds of bacteria, you will need an environment that is free from oxygen. 

How Can I Determine Whether the Fermentation Airlock is Working?

Once the yeast and the bacteria start working on the sugars and the fermentation process begins, there should be formation of CO2 gas which you should be able to see as bubbles moving via the fermentation airlock. 

The more active the yeast and the bacteria are, the more the formation of CO2 gas bubbles and the more you’ll see gas bubbles through the water. The gas bubbles will start becoming less frequent when the fermentation process starts slowing down. 

Under normal fermentation, the gas bubbles might exit through the airlock every few minutes as little burps. The absence of these gas bubbles indicates the end of the fermentation process.

What Else Can I Use Instead of Water?

Instead of using pure water, some people prefer using yeast-killing agents such as hydrogen peroxide or water that has been mixed with sodium metabisulfite. This is to prevent the chances of wild yeast entering the fermenter through the airlock. 

However, if you knock the container or incorrectly remove the airlock, some of this liquid might end up entering the fermenter and contaminating the wine, which is not the case when using just water. 

Can I Make My Own Airlock?

Yes, it is possible to make your own airlock. You only need to force a siphon pipe through a bung, and then gently force the bung on the neck of your fermenting container. Then, place the other end of the siphon pipe into a glass full of water. 

What if I Overfill or Underfill the Airlock? 

The exact quantity of water that you put in an airlock doesn’t matter. Provided the quantity of water in the airlock is enough to form a reliable barrier, the airlock will work fine. However, if you overfill the airlock, some of the water will be expelled outside when CO2 is bubbling from the fermenter. 

Should I Put a Cap on an Airlock Bubbler?

Many airlock bubblers come with a plastic cap which helps to prevent insects and dust from getting inside the fermenter. After filling the airlock bubbler with sanitizing fluid or water, gently force the cap into its place.

The small ridges or holes on the cap allow gas to escape while stopping dust and bugs from entering the fermenter. 

Is There Anything That Can Go Wrong With a Fermentation Airlock?

If you have ever heard of the beer geyser, that can also happen to a fermentation airlock. If the yeast and the bacteria are super active, the fermentation process can accelerate so quickly that the CO2 generation reaches a point in which it cannot escape through the airlock. 

In such a case, the beer can seep up into the airlock, completely blocking CO2 from escaping. The pressure might then build-up to the extent of creating a krausen blowout. 

Should I Use an Airlock Bubbler on a Secondary Fermenter?

Even if the fermentation process seems to have stopped, you still need an airlock bubbler in the secondary conditioning and fermentation. It is because the release of CO2 continues for several days even after the fermentation process has stopped.

Also, the airlock helps to compensate for the pressure difference due to the changes in the temperature. If you are conditioning the wine or the beer for an extended period, keep an eye on the water levels to ensure it hasn’t evaporated. 

Common Airlock Bubbler Related Issues 

You should regularly check your airlock bubbler during the conditioning or fermentation process. Here are some common issues related to airlock bubblers.

Airlock Full of Krausen 

The fermentation process forms a layer of foam known as the krausen. If the fermentation process is vigorous, some of this form is pushed through the airlock. If krausen forms, remove the airlock, clean it, and sanitize it.

Airlock Not Bubbling 

The bubbles of CO2 are expected to start flowing through the airlock in around 8 to 24 hours after pitching yeast. If you can’t see the bubbles, it doesn’t mean that the fermentation process hasn’t begun. However, it could mean a leak in the fermenter or the lid doesn’t seal correctly.

You can consider taking a gravity reading after two weeks to check whether fermentation has taken place as expected. CO2 is heavier than air, and so it will be protecting your alcohol from oxidation and infection.

Final Thoughts 

An airlock is a barrier between the outside world and the fermenting beer. Apart from protecting the beer from external impurities such as dust and bugs, it also allows the CO2 produced to escape. For protection against contamination, fill your airlock bubbler halfway.