How To Ferment In A Corny Keg

If you’ve been in the brewing community for quite some time or you’ve just recently begun your home brewing journey, we’re sure that you’ll be in complete agreement with us when we say that fermenting in a corny keg is becoming more and more popular.

How To Ferment In A Corny Keg

Fast becoming one of the best ways to undergo the home fermenting process, fermenting in a corny keg offers a variety of different benefits that other fermentation processes cannot (such as the conical process) and is extremely cost-effective, too.

Not to mention, it’s also one of the simplest fermentation methods, so it’s great for beginners.

In this article, we are going to be talking you through the process of how to correctly home brew using the corny keg fermentation process.

Along the way, we are also going to be sharing some additional tips and insights to help you get the most out of your home brewing process, including optimum temperature ranges and how to pull samples.

So, whenever you’re ready, let’s jump right in!

How To Ferment Using The Corny Keg Process

Even though you might have heard that using a corny keg is one of the most simple and effective ways of fermentation, using one can still feel a little tricky to get your head around – especially if you’ve never used one before.

For this reason, we’re going to be breaking down the process in stages, as well as providing you with some context on what a corny keg is, as well as what happens during fermentation.

Let’s check it out:

What Happens During Fermentation?

Fermentation can be an incredibly complicated process, but luckily, the corny keg method makes things much easier than they would otherwise be.

That being said, before we get into the nitty-gritty details of how to brew beer using the corny kegs, we first need to talk about what exactly happens during the fermentation process.

As mentioned earlier, fermentation involves yeast converting sugars from wort (or malt extract) into alcohol.

During this process, the yeast consumes oxygen and produces carbon dioxide gas, which causes the pressure inside the container to rise.

This is why, if you have a regular carboy, you will need to add airlocks to prevent the build-up of CO2 within the vessel.

However, because the corny keg has no neck, these problems don’t arise. Instead, the pressure builds up within the body of the keg itself, causing the liquid level to drop.

This results in the creation of a vacuum effect, allowing the yeast to grow even faster than normal.

As such, by removing the neck, you remove any potential issues with airlocks and allow the yeast to work at its full capacity.

This is why the corny keg is often referred to as a “vacuum” fermentation system.

It does require a bit of extra care and attention, especially if you’re new to home brewing, but once you understand the basics, it really is a simple process.

So, now that we know what happens during the fermentation process, let’s move on to discussing how to properly ferment in a corny keg.

What Is A Corny Keg?

Before we jump any further into this guide, we also think that it would be a good idea to quickly break down what a corny keg actually is.

Traditionally speaking, the equipment required for home brewing is relatively inexpensive, but some items may require special care when cleaning.

For example, fermentation buckets must be cleaned thoroughly after use because they contain living organisms.

Also, avoid using vinegar as a cleaner, as it contains acetic acid, which could damage the plastic.

The corny keg is a type of fermenter designed specifically for home brewers.

It consists of a cylindrical shape made from stainless steel, with a lid that fits snugly over the top.

These kids come in various sizes, ranging from 5 liters to 50-liter capacities. They are available online or from specialist retailers and typically cost between £30 – £50 each.

The advantage of using a corny keg is that it allows you to easily control the amount of oxygen entering the vessel, which means you can regulate the rate of fermentation.

Because there is no neck, the only way for oxygen to enter the vessel is via the cap.

By simply tightening the screw-on lid, you can reduce the amount of oxygen entering, thereby slowing down the fermentation process.

If you loosen the lid slightly, however, more oxygen enters the vessel, resulting in a quicker fermentation time.

There are other benefits to using a corny keg in place of a more traditional fermentation piece of equipment.

First, they are easy to clean. Unlike traditional fermentation vessels, the corny kegs do not have necks, so all you need to do is unscrew the lid and rinse away any residue.

Second, they are easy to store. The corny kegs are lightweight, meaning they take up very little space.

Third, they are safe to transport. Because they are light, they won’t break if dropped, and they are also resistant to extreme temperatures.

Finally, they are easy to fill. Simply open the lid, pour your wort into the vessel, replace the lid, and close it tightly.

You’ll then see bubbles coming out of the spout, indicating that the beer is ready.

Why Should You Use A Corny Keg as a Fermentation Vessel?

Now that we’ve covered what a corny keg is, let’s discuss why you should choose one instead of another method of fermentation.

There are two main reasons why you might want to consider using a corny keg:

1. Control Of Oxygen Levels

As mentioned above, corny kegs allow you to control the amount of oxygen that enters the vessel by adjusting the screw-on lid.

This means that you can slow down the fermentation process, allowing you to produce a better-tasting beer.

2. Easy Cleaning

Another benefit of using a corny keg is that it makes cleaning much easier than traditional fermentation methods.

Traditional fermentation pieces of equipment usually consist of a large tank with a removable neck.

When you’re finished making beer, you remove the neck, wash away any residual yeast and sediment, and put everything back together again.

While this is simple enough, it does mean that you will have to spend a lot of time washing these pieces of equipment.

With a corny keg, on the other hand, you just need to unscrew the lid and give them a quick rinse.

3. Simpler Than Other Fermentation Vessels

Finally, because corny kegs are so simple to use, you don’t need to worry about anything going wrong when you’re brewing.

All you need to do is open the lid, add your ingredients, and close it again. Once you’re done, you can leave the vessel alone until you’re ready to bottle.

Are There Any Drawbacks To Using A Corny Keg?

While the corny keg offers many advantages, it does have one major drawback: it doesn’t fit inside most fridges.

How To Ferment In A Corny Keg

So, if you want to keep your beer fresh, you will need to find somewhere else to store it.

Fortunately, this isn’t too difficult to achieve. There are several options available, including:

A Fridge/Freezer (The Best Option)

If you have the space and capacity, storing your corny keg inside a fridge or freezer is a great option because it will ensure optimum temperatures.

Still, keep in mind that as corny kegs tend to be on the larger side, you would need a fridge or freezer large enough to accommodate it.

Another benefit of storing your fermented beverages in an upright freezer is that you don’t have to worry about condensation forming on the outside of the container.

This is due to the fact that the temperature inside the freezer remains at around 0 °C, whereas the temperature outside the freezer will rise above freezing point during the winter months.

A Garage

If you don’t have a fridge or freezer big enough to store your corny keg – no problem!

Another great option that you could try in place of a fridge or freezer is to store your corny keg inside your garage.

Unlike other areas of the home, the garage is usually pretty cold as it usually doesn’t feature any of the insulation other parts of the home do.

This usually means that the temperature is perfect for storing your corny keg.

A Shed

This is very similar to storing your corny keg inside a garage. If you don’t have a garage or simply don’t have enough room in your one, then you could alternatively opt to keep your corny keg inside a shed!

As sheds are outdoors, it means that it can get pretty cold in them, which makes them the perfect place to store your corny keg to keep your beer nice and fresh while it is being brewed.

A Cool Cellar

Do you happen to have a regular cellar or wine cellar in your home? If you answered yes to that question, then you might want to consider storing your corny keg in it.

Cellars are great for storing a variety of different beverages due to the cold temperatures and lack of sunlight, which means that they are one of the most ideal places to keep a corny keg!

No matter where you decide to keep your corny keg, it is very important that you are always making sure to ensure that the corny keg is completely airtight before you place it in your storage area of choice.

Otherwise, moisture will form inside the container, causing mold to grow.

Alongside this piece of advice, when choosing where to store your fermented beverage, you should also be sure to take the time to consider the following factors:


Regardless of where you decide to store your corny keg, it is absolutely essential that you ensure that the area you store your corny keg offers cool temperatures, otherwise the beer held inside will spoil.

As a general rule of thumb, the storage location that you choose for your corny keg should be below 10 Celsius.


This factor ties in very closely to the one that we have just mentioned.

Storing your corny keg in a humid storage location will only cause the beer to spoil, so you should be sure to take this factor into account when deciding which area to keep it.


As we have already briefly touched upon above, you don’t want your freshly brewed beer to be anywhere near direct sunlight.

This is because the sun can warm the beer up and cause it to spoil or even grow mold on the inside of the keg.


Corny kegs can get pretty heavy, especially when they are filled with delicious home brewed beer!

For this reason, you’re going to want to make sure that you are going to be able to safely and easily access your corny keg, as well as be able to move it.

How To Prepare Your Keg Before Fermenting

Before you go ahead and begin using your corny keg, you should first take the time to make sure that it has been properly prepped!

With this being said, before you are able to use your corny keg, you are first going to need to bend or cut the liquid dip tube (a component that all corny kegs come with) so that it has been positioned away from the bottom of the keg.

If you do not do this, the keg will end up catching all the trub (which is a type of sediment that occurs during brewing that contains dead yeast and other things) while you transfer it to the secondary vessel!

In order to do this correctly, we recommend that you remove around 2 inches or so of your dip tube.

By doing so, you will be ensuring that there will be around 1 inch of space between your keg and the ground, which will then help to guarantee that no trub gets caught up inside your fermented beer when the time comes for you to move it from the corny keg to its next vessel.

Keep in mind that the amount of tube you cut off will vary from keg to keg, so we recommend cutting in small amounts to ensure you do not take too much off.

Alongside this, you should also make sure that you are keeping your keg temperature-controlled, and you can do this by storing it in a place that is below 10 degrees Celsius, which we have already talked you through above.

The final preparation step that you should take to make sure that your corny keg is ready to ferment your beer is to make sure that you have a blow off tube or spunding valve that allows you to ferment your beer under pressure.

How To Brew Beer With A Corny Keg

To begin, you will need to start off by purchasing a corny keg.

These are available online or from local stores like, where you can find everything you could possibly need to make your own beer.

You may also want to consider buying a second-hand keg, as you won’t necessarily need a new one every time you brew.

Once you’ve purchased your keg, you will need to fill it with water. It’s recommended that you use filtered tap water, however, if you prefer, you can always use distilled water instead.

When filling the keg, ensure that you leave enough space between the top of the keg and the surface of the water.

If you do not leave enough room, the pressure created by the rising CO2 will cause the contents to overflow.

Once you’ve filled the keg with water, place the lid on the top and secure it tightly. Then, wait until the water has been completely absorbed by the keg.

Once the keg is fully saturated, you should see bubbles forming around the edge of the lid. After a few minutes, you should be able to hear the sound of the CO2 escaping from the keg.

Next, you’ll want to connect your hose to the keg so that you can siphon some of the wort out of the keg.

Make sure that you only pull the amount of wort that you actually intend to use for brewing.

Otherwise, you risk contaminating the rest of the batch.

After you’ve pulled the required amount of wort, disconnect the hose and then attach the spigot to the keg. Now, you’re ready to start adding your ingredients!

You should now be able to pour your malt extract into the keg, followed by your hops. However, before doing so, you will first need to sterilize the keg.

In order to sterilize the kegs, you will need to heat them up using an oven or stove top burner.

The best way to do this is to preheat the oven to 200 degrees Celsius (400 Fahrenheit). While the oven heats up, you’ll want to place the keg directly onto the hot element.

When the oven reaches temperature, turn it off and wait 30 seconds. Next, open the door of the oven and carefully lift the keg out.

Place the keg back down on the hot element and wait another 30 seconds.

Finally, close the oven door and let the keg cool inside the oven for about 10-15 minutes.

Once the keg has cooled, you can proceed with pouring your wort into the keg.

When all of your ingredients have been added, you should now be ready to pitch your yeast! This brings us to our next section.

Pitching Your Yeast Into The Wort

The next step is to pitch your yeast into the wort. This is done by slowly pulling the spout of the keg towards yourself while holding the end of the hose.

Make sure to keep the end of the hose away from the sides of the keg, otherwise, you run the risk of spilling the wort.

As soon as you feel resistance when pulling the spout, stop and allow the yeast to fall into the wort. Repeat this process until all the yeast has fallen into the wort.

Now, you’ll want to cap the keg and store it in a warm location for at least 12 hours. During this time, the yeast will begin to ferment the wort.

You’ll know that fermentation has begun once you notice the bubbling activity coming from the keg.

If you’ve pitched your yeast correctly, you should notice the foam at the bottom of the keg rise up and form a small layer over the liquid.

As long as there is still plenty of air in the keg, it shouldn’t take too long for the foam to reach the top of the wort. If you don’t see any foam within a couple of hours after pitching your yeast, you may want to add more yeast.

Now that you’ve pitched your yeast into the worts, you should be ready to ferment.

Fermentation And Conditioning With Your Corny Keg

During fermentation, the yeast will eat up the sugars contained in the wort and convert them into alcohol and carbon dioxide gas.

How To Ferment In A Corny Keg

As the fermentation process continues, the volume of the wort will decrease. At the same time, the level of dissolved oxygen will increase.

Eventually, the beer will become very foamy due to the presence of large amounts of sugar-eating yeast cells.

As the yeast eats through the sugars, they also produce various flavors and aromas. These include fruity esters, spicy phenols, caramelized malts, and other complex compounds.

While the fermentation process takes place, it’s important to maintain good sanitation practices. For example, make sure to clean the surface of the fermenter regularly.

Also, make sure not to leave the lid off when transferring wort to the fermenter.

After the fermentation process is complete, you’ll want to transfer the fermented beer into a secondary vessel such as a carboy or bucket.

Once the beer is transferred to the secondary container, you’ll need to condition the beer for several weeks before bottling.

Why Should You Ferment Under Pressure?

If you’ve already begun doing some research into fermenting with a corny keg, we’re sure that you will have come across the term “pressure-brewing”.

Essentially, opting to use a corny keg as a fermentation vessel allows your beer to ferment under pressure due to the design of the corny keg.

This is highly beneficial because it means that the amount of ester produced during the fermentation process

The Optimum Fermentation Temperature

As mentioned earlier, the ideal storage temperature for a fermented beverage is below 10 °C.

However, because of the risk of contamination, it’s advisable to keep your beer stored at 1 °C or lower.

This may seem a lot colder than normal, but remember that the temperature inside a refrigerator is usually between 5 °C and 7 °C.

For this reason, by keeping your beer in a cooler environment instead of an environment that is warm or very humid, you’re actually going to be making sure that your home brewed beer will be kept safe from contaminants.

If you live in a cold climate, you might be able to use a thermostat to help regulate the temperature inside your home.

Alternatively, you could try hanging a wet towel over the door of your fridge to create a barrier against heat loss.

The humidity level within your home will affect how long your beer lasts.

For example, if there’s a high concentration of moisture present, the yeast will start to produce alcohol faster, which means that the beer will become stronger quicker.

If you want to avoid this, simply ensure that your home is well ventilated.

The light levels can also play a part in determining how quickly your beer ages. Beer exposed to lots of bright sunlight will age much slower than beer kept in dark conditions.

With all of that being said, if you live in a particularly sunny area, you might want to invest in some sort of cover to protect your beer from direct exposure to the sun.

Ideally, as we have already mentioned above, you should try to keep your corny keg inside a fridge, freezer, cellar, basement, or even a garage.

As a side note, it’s important to note that sunlight has two effects when it comes to fermentation. Firstly, it causes the yeast to consume more sugar, thereby producing more alcohol.

Secondly, it causes the yeast cells to die off, leaving behind dead yeast particles called “lees”.

These lees can then cause problems with your beer and alter the taste, so it’s important to remove them as soon as possible or avoid them from occurring entirely by following our advice and keeping your corny keg stored somewhere that does not get any direct sunlight.

Conditioning Your Beer Correctly

To condition the beer, simply rack the beer from the primary vessel to the secondary one. You can do this using either an auto-siphon or a manual pump.

If you’re not sure what the difference is between the two, read on for a quick breakdown of the two:

The first option is an automatic siphon. With this type of device, you place the end of a hose in the bottom of the vessel containing your wort.

Then, you attach the other end of the hose to a faucet. As long as there is pressure in the line, the liquid will flow from the vessel into the container.

The second option is a manual pump. These pumps usually consist of a plastic tube connected to a rubber bulb.

To operate the pump, you squeeze the bulb which forces air out of the tube and into the vessel.

Once the desired amount of liquid has been transferred, all you will need to do is simply release the pressure by releasing the valve!

Which is best? Well, that depends on what you’re looking for. If you just need to transfer some wort from one vessel to another, then an automatic siphon will suffice.

However, if you need to move large quantities of liquid, then a manual pump may be more suitable.

In the case of using a corny keg, you’re likely going to find that a pump works better, although this will ultimately come down to your personal preference.

Once the beer has been racked into the secondary vessel using your equipment of choice, you’ll need to aerate it.

Aeration allows the CO2 produced during the fermentation process to escape. It also helps prevent the formation of sediment in the beer.

When aerating the beer, use a sanitized airlock on the secondary vessel. Keep the temperature around 50 °F (10 °C) so that the beer doesn’t get too hot or cold.

The ideal temperature range for conditioning beers is between 45 °F – 55 °F (7 °C – 13 °C).

When the beer reaches its target gravity, it’s time to bottle. Make sure to keep the bottles and caps cool by storing them in the refrigerator.

Before bottling, you’ll also want to prime the bottles with some priming solution.

This will ensure that the bottles are completely filled with beer. After bottling, allow the beer to sit undisturbed for about two weeks before drinking.

How To Cold Crash With A Corny Keg

Cold crashing is a technique used to reduce the amount of sediment that forms in your beer after fermentation.

It involves fermenting your beer at a higher temperature (around 20 °C) for a shorter period of time. The longer you leave your beer at this temperature, the less alcohol it will contain.

To do this, you’ll need to transfer your beer into another vessel while it’s still warm. Once cooled down, you can either bottle it or put it back in your original fermenter.

You can also use a secondary fermenter to cool your beer down. This is especially useful if you have a large volume of beer.

Below, we are going to be breaking down the process of cold crashing below:

How To Cold-Crash: Step-by-Step Instructions

  1. First things first, you’re going to want to begin by transferring your beer into a sanitized container such as a carboy or bucket.
  2. Then, after you have done this, you can then proceed to place the container in an ice bath until it reaches around 4 °C or even lower.
  3. Once you have done this, you can then go ahead and remove the container from the ice bath and allow it to sit for a few hours before transferring it to a refrigerator.
  4. When it’s been chilled down, you can then proceed to store the beer in your fridge.
  5. You should only have a cold crash once. After that, you can either continue to ferment your beer or let it mature naturally.

As a side note, keep in mind that the cold crashing process can actually make your beer taste a little sweeter because it reduces the number of sugars inside the yeast.

Many people find that this only helps to elevate the overall flavor of the beer, and makes it more appealing to a variety of different palettes.

In addition to this, while on the topic of sweetness, if you want to add extra flavor to your beer – you can add fruit purée or other ingredients to it during the primary fermentation stage, which is a great option for the spring or summertime.

How To Store Your Homebrew Safely

So, even though it is very important to make sure that you are fermenting your beer correctly using your corny keg, it is also very important that you are making sure that you are correctly storing your home brews, too.

Luckily, the good news is that there are a number of ways to store your home brew safely after the fermentation process is over and successfully completed.

For instance, there are some people who prefer to use glass bottles, while others favor using plastic bottles.

Whichever method you choose, make sure that you follow these guidelines that we are going to be outlining below:

  • Always sterilize all equipment used for fermenting.
  • Use sterile water to rinse out the bottle after filling it with wort.
  • Never reuse any equipment that was previously used for fermenting. It’s best to throw away anything that’s been contaminated with bacteria.
  • Always wash your hands thoroughly after handling your wort or beer.
  • Make sure that you clean your bottles properly. You can do this by washing them in hot, soapy water and rinsing them under running tap water.
  • Always keep your bottles upright when storing them in the fridge. This helps prevent oxygen from getting into the headspace, which would otherwise allow bacteria to grow.
  • When storing your beer in the fridge, always leave a little space above the liquid. This allows carbon dioxide gas produced during fermentation to escape, preventing the formation of bubbles.
  • To avoid oxidation, don’t place your beer directly on top of other foodstuffs. Instead, put it in an airtight container before placing it in the fridge.
  • To avoid contamination, always keep your beer stored at a cool temperature. However, if you have access to a freezer, it’s better to store your beer in there rather than keeping it in the fridge. The reason for this is that the cold temperatures of a freezer slow down the growth of harmful microorganisms, such as mold.
  • If you’re planning on drinking your beer within a few weeks of bottling, you should probably store it in the fridge. However, if you plan on waiting longer than that, it’s better to transfer it to a cellar or wine rack instead.

How To Bottle Your Homebrew Beer Correctly

Last but not least, after you have finished the fermentation process using the corny keg method and your beer has been brewed, you’ll then need to make sure that you are bottling it.

Any bottle will work fine, although most homebrewers find that glass bottles work best.

Before bottling, you’ll want to allow the beer to condition for a few days before drinking.

During this period, the yeast will continue to work its magic, producing additional flavor and aroma compounds.

Once the beer has conditioned sufficiently, you can begin preparing bottles for packaging.

To bottle correctly, we recommend that you fill each bottle with the appropriate amount of beer using a beer dropper.

Then, wipe the rim of the bottle with a paper towel before attaching the top so that you can ensure a tight seal.

It’s very important that you make sure that the cap is fastened secretly to your bottle, otherwise, moisture will be able to get inside and affect the integrity of your home brewed beer, and even potentially cause mold to begin growing.

Then, as soon as you have finished capping all the bottles containing your beer, you will then need to allow the bottled beers to sit for a period of around 2 weeks (or even longer) before you begin drinking them.

During this time, the yeast will continue to work its magic, converting the remaining sugars in your beer into alcohol, which will only enhance the flavor of your beer.

However, if you’d like to speed up the process, you can add a small amount of priming sugar (such as corn syrup) to your bottle. This will help kick-start the fermentation process and produce a faster-maturing brew.

When the time comes, all that will then be left to do is to actually drink your home brewed beer! When the beer has finished conditioning, simply remove the cap and you can enjoy it!

The Bottom Line

All in all, home brewing isn’t just about making tasty beverages; it’s also about learning new skills and having fun along the way – and we hope that we have shown you how to streamline the fermentation process by using a corny keg.

Even though it might seem a little confusing at first, by following our simple guide, you’ll be able to get started right away. So what are you waiting for? Get brewing!

Thanks for reading.

Andrew Carr