Cold crashing beer is a tried and true way to get crystal clear beer faster. It’s also a good way to ensure sediment and suspended yeast fall out of the beer and settle at the bottom of the fermenter before bottling or kegging. I cold crash all of my beers before packaging as do the pros.
What is Cold Crashing?
Cold crashing is the practice of chilling your beer down to near freezing after fermentation has completely finished. It’s the last thing you should do just before kegging or bottling. Be sure fermentation and conditioning are entirely wrapped up before crashing. You want the yeast to have adequate time to clean up after itself after fermentation is completed. I usually wait 10-12 days after pitching.
Why Cold Crash?
Flavor and clarity. You don’t want avoidable yeast or hops in your finished product. Your beer will taste cleaner if unwanted compounds fall out of suspension. With yeast and sediment falling out of your beer, it will obviously jump-start the clarification process. Sure your beer will slowly clarify over time in kegs or bottles but cold crashing will prevent packaging a lot of sediment to begin with.
Cold crashing also aids in clog-free transfers. Cold crashing helps clumps of protein, grain matter, and hops fall to the bottom of the fermenter so you don’t suck them up into your auto-siphon or even worse, clog the poppets on your corny keg. If you’re doing any sort of closed transfer with a conical fermenter, cold crashing will help ensure a smoother process. If you’re into brewing IPA/NEIPA, cold crashing is absolutely essential when it comes to the conditioning phase.
How To Cold Crash Homebrew
Place your fermenter directly in a fridge/freezer and get the beer as cold as possible without actually freezing. Shoot for about 32-35°F for 24-48 hours. Remove and proceed with kegging or bottling. Don’t worry, there will still be enough yeast present after crashing to naturally carbonate your brew.
If you keg your beer, you can in fact cold crash directly in the keg in your kegerator. The only downside is you’ll miss the opportunity to filter out any yeast/sediment before kegging (which will build up in the bottom of the keg and risk clogs). Cold crashing before kegging also ensures your beer is super chilled and ready to take on CO2 for forced carbonation immediately.
Avoiding Oxygen Suckback
When the temperature of your beer in a fermenter drops dramatically, it creates a vacuum that will actually pull air/oxygen into the fermenter. Oxygen is of course a beer killer and will deteriorate the delicate flavors/aromas in your brew.
A sealed vessel will prevent oxygen suck-back but also behaves like a vacuum sealer and poses a risk of collapsing your fermenter in the most extreme cases. One solution to prevent this would be to seal off and pressurize your fermenting vessel (likely a conical or keg) with 5-7 PSI of CO2 to offset the pressure drop. If you ferment in a non-pressurizable vessel (bucket or carboy), you can attach a CO2-filled mylar balloon to your airlock so any suck-back is replaced with CO2 instead of oxygen.
How To Cold Crash with No Fridge
If you don’t have access to an extra fridge. (God knows my wife would kill me if I tried to stuff my fermenter in our fridge), you can place the fermenter in an ice bath and or wrap it in water-soaked cold towels. Continue to monitor and pour fresh ice water over the towels periodically. I used to use a cheap 20-gallon plastic basket for cooling hot wort in the kettle—it’s a phenomenal option for cold crashing as well.
If it’s winter…it’s your lucky day. Place the fermenter on the deck or in the garage! Just make sure your beer doesn’t freeze.