Thursday, August 6, 2015

The Art Of Cold Crashing Your Beer

The majority of home brewers that I've met over the years have never bothered to filter their beer before packaging it. The truth is most of the home brewed beers I try at club meetings and competitions are remarkably clear without ever having undergone any filtering at all. As an avid home brewer myself I stopped thinking about filtering my beer a long time ago. Like so many other home brewers did before me I discovered that really clear beer could be packaged by just following a few easy steps.

Enjoy Your Beer Cold, Clear And Colorful
What Is Cold Crashing?

I'm not really sure how the term 'cold crash' originally became part of the home brewing vocabulary though. I understand that the 'cold' part of the terminology refers to dropping the beer's temperature down to only a few degrees above freezing. I guess the 'crash' part of the terminology refers to having to do so as quickly as possible. The physics behind cold crashing is what causes the yeast, proteins and other solids that are otherwise suspended in your beer, to clump together, become heavier and eventually fall out of suspension. All those unwanted particles then sink to the bottom of the fermentor where they form a compact layer of trub leaving the beer above it clean and clear.

Never Worry About Chill Haze Or Floaties Again
Why Cold Crash Your Beer?

I cold crash all of the beer I brew to help give it a crisper, cleaner more colorful finish. Although chill haze isn't considered to be much of a problem when packaging some styles of wheat or darker colored beers, it can be an issue in lighter colored beer styles. While there is no adverse affect to beer flavor or taste due to the presence of chill haze in a glass of beer it is considered to be a flaw by most brewers. If left unchecked chill haze can cause 'floaties' to develop, clumps of yeast and protein matter that are bound together but are not heavy enough to ever settle out of your beer. Instead these clumps will just end up floating around inside your glass suspended in hazy beer for all to see.

Nobody Wants To See Floaties In Their Beer
When Is The Best Time?

Once my beer has reached it's final gravity signalling the end of fermentation, I start the cold crash cycle by lowering the temperature controller setting down to 40F. I do this to prevent the controller from initially undershooting the 40F temperature and unintentionally freezing the beer. The next day I drop the temperature down to 34F and let the beer sit there for up to a week before kegging it while it's cold. Force carbonating beer while it's cold is very efficient because Co2 dissolves much easier in a cold liquid.

Another benefit of force carbonating refrigerated beer is that the beer inside the kegs will continue to cold crash as it's being carbonated. This additional time that the beer spends held near 34F allows any remaining yeast, proteins or other solids to sink to the bottom of the keg. Only the smallest amount of debris should settle to the bottom of the keg at this step. The goal now is to serve clean pours so you don't want to be sucking up any trub into your first few beers.

Force Carbonate The Beer Cold, Clean And Quickly

After the moving the clean beer from the fermentors to the kegs you should now see a compact layer of trub stuck to the bottom of the fermentor. The trub layer acts as a trap that holds coagulated yeast, hop and protein debris inside the fermentor preventing any of the debris from getting into your kegs. If the debris were allowed to mix in with the beer again on its way to filling the kegs it may be impossible to prevent chill haze from forming in your finished beer. The debris also contains astringent tannins and other material that in significant enough amounts will contribute to the development of off flavors in the beer.

The Trub Layer Can Keep Debris From Entering The Finished Beer

Depending on how often you get to brew it can take several years to perfect every step in your brewing process. From grain and yeast selection to mash temperature to boil length and volume it's easy to see how a brewing process is made up of many different steps. With the goal in mind to brew the clearest cleanest tasting beer possible there are a few other tricks to keep in mind in addition to cold crashing your beer.

Tips For Producing The Clearest Beer
  • Adding WhirlFloc or other fining agents to the boil kettle just before flameout will help the proteins, tannins and hop particles to clump together while the wort is still boiling. 
  • Putting hop additions into fine mesh hop bags is also a good way to reduce trub in the kettle during the boil.
  • Using a whirlpool to compact the kettle trub so it doesn't get pulled along into the fermentor where it takes up room. 
  •  Waiting 20 or so minutes for any kettle trub to fall to the bottom of the kettle before moving the clean beer above it to the fermentors. Once the whirlpooling has stopped it can take that long for the smallest trub particles to settle out of the wort into a neat pile on the bottom of the kettle. 
  • Compensating for fermentation trub loss by transferring an additional quart of wort per five gallons of packaged beer to the fermentor reduces the chance of trub getting into the packaged beer.  

Whirlpool, WhirlFloc And Let Settle Before Transferring The Beer
  • Cold crashing the fermented beer before packaging it gives the yeast and other debris time to drop out of suspension and settle to the bottom of the fermentor. Depending on the flocculation rate of the yeast used to ferment your beer it can take anywhere from a few days to a few weeks for the yeast to settle out.
  • Carbonating your beer while it's still cold allows the cold crash process to continue as the beer is being carbonated. Since Co2 is more easily absorbed by cold liquids your beer will also carbonate faster than if it were carbonated warm.

Clearing Your Beer With Gelatin

After taking as much care as possible to remove yeast and trub from your beer there may be times when adding gelatin to the beer can help to speed things up. Since gelatin is made from animal parts, if you are gluten intolerant, or suffer from the symptoms of Celiac Disease, you definitely have no reason to worry when using gelatin to fine your beer.

1 Teaspoon Of Unflavored Gelatin In 1 Cup Of Water

I use Knox brand gelatin because it is easy to find at stores in my area and it is inexpensive to buy and use. Each box of gelatin contains 4 envelopes and each envelope contains 2 teaspoons of gelatin. A teaspoon of gelatin mixed with 1 cup of water and heated to 150F is enough to clear 5 gallons of beer. All that is needed to prepare the gelatin for use is a microwave safe measuring cup, a measuring spoon, a thermometer and a way to heat the mixture of gelatin and water to 150F.

Before adding gelatin to the beer I like to keg and carbonate it cold for a few days. The colder the beer is when the gelatin is added the more chill haze will be present for the gelatin to work on and the better the job it will do clearing the beer up. 

   1. Start by filling the measuring cup with 1 cup of water and then sprinkling 1 teaspoon of gelatin powder over the top of the water.

   2. I like to wait a few minutes for the gelatin to bloom before stirring it thoroughly into the water.

The Gelatin Will Bloom After Sitting A Few Minutes On The Water

   3. Heat the mixture in a microwave oven using short 15 to 20 second bursts, stirring it in between bursts, until the temperature of the gelatin mixture reaches 150F. It is not recommended to heat the mixture above 170F when preparing gelatin for fining beer.

Pour The 150F Gelatin Mixture Directly Into The Cold Beer

   4. Once the gelatin has been poured into the beer snap the keg lid back on and then purge the keg with Co2 to eliminate any oxygen from the keg. Keeping the kegged beer cold and undisturbed should clear the beer up in a matter of days.

Depending on the amount of of trub that will eventually settle out of the beer to the bottom of the keg, the first pour or two may be cloudy with gelatin and trub. At 36F the beer should clear in as little as 48 hours. I usually have time to wait for the beer to clear on it's own and only cold crash my beer. But when pressed for time using gelatin to quickly clear the beer of yeast and chill haze is a good option to have available too.  

In Conclusion

Every time I transfer wort or beer from one vessel to another I see it as an opportunity to reduce the amount of trub it contains and a way to further clean up the finished beer. Preventing chill haze and floaties from ruining the appearance of an otherwise perfect glass of beer is just one of the benefits of removing trub as you go. When using a plate or counter-flow chiller to cool your wort its also a good idea to keep their insides as clean as possible in order to prevent clogging and ensure a more effective sanitization.

Knowing your brewing system is also very important when it comes to calculating your wort and beer volumes. How much extra wort is needed in the kettle to allow for boil off, hop absorption and kettle trub loss? How much extra wort should you transfer to the fermenter to allow for fermentation trub loss? After spending time brewing a batch of beer the last thing you want is to come up short on the amount of beer you'll have to package. The crush of your grains, the chemistry of your brewing water and other things influence the clarity of your beer and make great topics for another day. Based on the information presented here today and a little effort you too will master the art of cold crashing your beer. 


  1. The gelatin should not hurt a person with Celiac disease. The beer on the other hand most likely will. I would expect people with serious autoimmune diseases to be cautious around beer.

  2. Isinglass is far better than gelatin for fining beer.

    1. Isinglass may work somewhat better than gelatin in clearing Ales but it is not recommended to use in Lagers.

  3. I'm wondering if it's necessary to boil the water for the gelatin finings then let it cool to mixing temp so that it's sterile?

  4. Boiling the water used for the finings, then cooling it to 160F, before stirring in the gelatin would eliminate any possibility of beer contamination.

  5. I've used gelatin on every brew (about 15 now). I Keg then chill 24 hours, then mix up half packet of Knox to 1/2 cup water. Microwave to 150°, pour into keg! Hook up the gas only to 30° Psi for 24 hours. Turn down to 8psi and pour the first couple pints. Drink clear beer.