You have probably heard the term «cold crash» or just «CC», but what does it actually mean? And why do we do it? Put very briefly, cold crash is the term we use for chilling the beer towards the end of fermentation. By dropping the temperature quickly towards the end, proteins, yeast and other particles in the finished beer clump together and fall to the bottom. You can end up with a crystal-clear beer.
What temperature for cold crashing?
A cold crash is normally done at 0–4°C. The colder you can get it, the better (without freezing the beer, of course). When the beer has finished fermenting, it naturally contains a certain amount of alcohol. This alcohol also prevents it from freezing, so feel free to go all the way down towards zero degrees if you have the equipment for it.
A glycol chiller is purpose-built for this, and can also control the temperature of several fermenters at the same time. A Ferminator fermentation chamber is also very popular, or a fridge if you have a spare one.
How long should you cold crash?
How long you run the process is largely up to the brewer, but you will see results after a day or two. Beyond that, there is no problem chilling for even longer. Styles such as pilsner and similar need a good deal longer, mainly because they need cold storage to mature, but also because they should be completely crystal clear.
Hazy beer styles also benefit from a cold crash, mainly to let hop and yeast residue settle out. This should not affect the haze or give a clear beer, but it will separate particles from the finished beer. Heavily dry-hopped beers in particular benefit from this, and you can get more beer out of the fermenter, as the hops settle at the bottom of the fermenter instead of at the bottom of the bottle or keg.
Benefits of cold crashing
- Particles and chill haze settle out, and you get a much clearer beer in a short time.
- Hops and yeast settle at the bottom, so fewer particles are carried over when transferring to bottles or a keg. As you separate the hop debris from the rest of the beer, a cold crash can even help you get more beer out of each batch.
- The beer is already chilled for fast and stable carbonation in a keg. Cold beer absorbs CO2 more easily than warm beer.
- Bottom-fermented beer needs a period of cold storage (lagering) to mature properly.
Precautions and tips for cold crashing
There are, of course, a couple of things to be aware of when it comes to cold crashing. When the temperature drops quickly, a vacuum forms as the air in the fermenter contracts. This is often called «suckback», and can damage both the beer and, not least, the fermenter if precautions are not taken.
If you have a blow-off on the fermenter, meaning the airlock has been replaced by a tube in a container of water or Star San solution, this can be drawn into the fermenter and mix with the beer.
If you close off the airlock so the fermenter is completely sealed, in the worst case the whole fermenter can implode. This can happen with both plastic and steel, and should be taken seriously.
If the airlock is left on as normal, air will be drawn into the fermenter when the cold crash starts.
You would have to be very unlucky for damage to occur from air getting in, but be aware that there is still a risk of drawing in contaminated air (wild yeast, bacteria and other unpleasant microorganisms that want a taste of your beer), or that a lot of air can increase the risk of oxidation.
There are several ways to prevent suckback. Homemade solutions, such as filling a balloon or bag with CO2 and fitting it to the airlock or similar, are a simple and cheap option.
If you have a fermenter designed for pressure, this should not be a problem. You can then simply apply a little overpressure to the fermenter before the cold crash starts. Alternatively, you can fit a special type of PRV / safety valve that compensates for vacuum. See our 1.5" Tri-Clamp vacuum PRV. It is also available in a 34mm Tri-Clamp version.
Ferminator
Ferminator Basic and Connect are by far our best-selling products for temperature control during fermentation, and they also make cold crashing possible. These are affordable fermentation chambers with an integrated element for both cooling and heating. Ferminator Connect can be controlled via Wi-Fi.
