How to Keg Beer Part 4: Cold Crashing and Force Carbonating

One of the key benefits of kegging your beer is that you’re able to cold crash and force carbonate your homebrew fairly easily. Cold crashing ensures all the hop, yeast and protein particles drop out of suspension, creating clear beer, while force carbonating allows you to reach the perfect levels of carbonation each and every time. Knowing how to force carbonate a keg of homebrew can also save you a lot of time.

If you’ve been following the previous parts of our essential guide on how to keg beer, you should now have a keg filled with beer — check part 3 if you need a refresher. Part 4 of the guide takes you through the various options you have for carbonating your beer. This guide assumes you have not previously cold crashed your beer in the fermenter — but if you have, simply skip the cold crash step detailed below.

Cold Crashing in the Keg

Many homebrewers aren’t able to fit their fermenting bucket or carboy in the fridge or kegerator to cold crash. The easiest solution to this issue is to cold crash your beer in the keg. Once the keg has been filled and sealed, it’s a simple matter of placing the keg either in a normal fridge, or in your kegerator.                                                                                                                                      When learning how to keg beer, it’s important not to neglect cold crashing. Not only does cold crashing aid with clarity, but cold beer absorbs co2 far easier than warm beer, allowing you to carbonate more efficiently. It’s best practice to drop your beer to at least 5℃.                                 While cold crashing, you will find that your keg loses pressure, as the co2 you used to seal it is absorbed into the beer as it cools down. You can keep the co2 connected to the keg while cold crashing to maintain 10 psi and ensure the lid remains firmly sealed.

How to Force Carbonate a Keg

It’s best to start the process of carbonating once your beer has chilled right down. There are a number of methods you can use to force carbonate your beer in the keg, each with their pros and cons. The classic set and forget works well for those not in a rush, while the shake and carbonate can have your beer ready to drink in under an hour. For the middle ground, burst carbonation works well. The following methods assume you’re using a corny keg — smaller vessels will be discussed below.

Set and Forget

The easiest and most reliable method of force carbonating a keg normally takes around 2 weeks to fully carbonate. While it takes a while, it guarantees that you’ll hit the exact level of carbonation you require.

Typically, you’ll hook up your co2 to the keg, set the regulator at serving pressure, between 8–12 psi, and let it slowly carbonate over the course of 2 weeks or so. Carbonation charts can be used to ensure you get the exact level you want, with allowances made for temperature.

Shake and Carbonate

This rough and ready method can have your beer fully carbonated in minutes rather than weeks, and is a popular choice for brewers in a rush. It involves hooking the co2 up to a keg of cold beer, cranking the pressure up to 30 psi, and shaking, rolling or rocking the beer for 30 minutes or so. Co2 is more readily absorbed into beer when it’s agitated in this way, due to the larger surface area of the beer.

The trade off is that it’s all too easy to over carbonate your beer, leading to a foamy mess in the glass. Some keen tasters also note a ‘carbonation bite’ during the first few hours of drinking after force carbonating. Another potential issue is that beer can very easily enter the co2 regulator if the gas tank runs out halfway through, though a check valve on the gas disconnect will prevent this issue.

Before serving, release the excess pressure in the keg using the release valve and set your regulator to serving pressure, around 12 psi.

Burst Carbonation

The finally method enjoys the best of both worlds, with beer fully carbonated and ready to drink within 3 to 5 days. After cold crashing, hook up your co2 and crank it up to 30 psi for 24 hours. This should get your beer to around 75% carbonated, so lower the pressure to a serving pressure of around 12 psi to finish it off over the next 3 or 4 days.

To speed things up, you can hit it with a burst of higher pressure for a shorter time. For example, 12 hours at 40 psi, or 8 hours at 50 psi. Trial and error works best here, with experimentation encouraged until you find what works best for your setup.

Carbonating Smaller Kegs

It’s worth noting that smaller kegs will require less time to carbonate, so handle with care. You can use 16 gram co2 cartridges to carbonate smaller amounts of beer, with one cartridge typically carbonating 4 litres of beer. Again, any of the methods above will work, the safest being set and forget, which can be completed within 2 or 3 days.

If you plan to shake and carbonate, a check valve on the gas disconnect is essential. It won’t take long for a 16 gram cartridge to empty if set at high pressure, and if you’re shaking the keg, there’s a chance the beer will escape into the regulator, destroying it.

Nicely carbonated keg beer is a true delight and a great way to serve beer at home. The fifth and final part of our essential guide on how to keg beer will take a look at how to serve and finally enjoy your homebrew.