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8 Things You Should Know About “Cold Crashing” Beer

Beer clarity is essential for many beer styles, and can make or break a beer in a competition. There are many ways to help clarify your beer, and some are easier than others.

A semi-advanced home brewing technique used to improve clarity is a process called “cold crashing.” Just hearing the term may bring to your imagination a much different process than what is actually involved in cold crashing.

If done correctly, cold crashing will give your beer a clean, crisp appearance.

1. What is Cold Crashing?

Cold crashing is a process used to clarify home brewed beer by cooling it to near-freezing temperatures before bottling. Cooling the beer actually encourages yeast and other sediment suspended in the beer to flocculate (group together) and sink to the bottom.

This allows you to transfer the beer out of the fermentor for bottling while leaving behind much of the sediment that would cause a haze in the finished beer.

2. How is Cold Crashing Done?

To cold crash a beer you simply need to place it in a temperature-controlled environment. A lagering fridge that is outfitted with a temperature controller (this controller is most often recommended) is ideal. Regular refrigerators actually fluctuate in temperature which causes problems with the beer, while a fridge with a controller is held at a constant temperature.

The cold crashing temperature that is recommended varies from 33 degrees F to 40 degrees F, with 38 degrees F being the most common.

The recommended duration of cold crashing also varies. Some brewers say that only a day or two is needed, but it is most common to cold crash for one week.

3. Can Both Lagers and Ales Be Cold Crashed?

Although cold fermentation is only done for lagers, cold crashing can be done on both ales and lagers.

4. When Should I Cold Crash?

Cold crashing should not be done until fermentation has finished. This is usually determined by using a well-sanitized hydrometer or a refractometer to measure the specific gravity of the beer. When the specific gravity is steady for three days in a row fermentation can be considered complete (if gravity is decreasing from one day to the next, fermentation is still taking place).

Cold crashing can be done in either the primary fermentor or the secondary fermentor, although it is probably most common to see it done after secondary fermentation to encourage an even clearer beer.

5. When Should I Dry Hop if I Plan to Cold Crash?

This is a common question that comes up with cold crashing: should the dry hopping process should be done differently.

“Dry hopping” is the practice of adding hops directly to the fermentor for the last few days of fermentation to impart some hoppy aroma to the beer. The question is whether the dry hopping should be done during the last few days of the cold crashing process rather than the last few days of the fermentation, before cold crashing.

There is concern that the hop acids which give the beer its hoppy aroma will dissipate over time, and adding them before the additional cold crashing time will reduce the overall hop aroma of the beer. While this might happen to a limited extent, it is generally advised that the dry hops be added at the regular point at the end fermentation. The cold temperatures of the crashing should prevent much of the aroma being lost.

6. Will Bottle Carbonation Take Longer if I Cold Crash My Beer?

Yes. Since cold crashing will remove some (but not all) of the yeast from the beer it will take longer to carbonate the beer in the bottle.

Bottle carbonation is done by yeast consuming the priming sugar that is added to the beer while bottling. The yeast gives off alcohol and carbon dioxide as a result, carbonating the beer. With fewer yeast cells it will take longer for this process to occur. Instead of setting aside the regular two weeks for carbonation you might be waiting three or four weeks, or sometimes even six weeks depending on the beer style.

7. Are There Other Methods of Clarifying Beer After Fermentation?

There are several different clarifying agents (or “fining agents”) that can be added to the beer after fermentation to promote clarity. Some examples are gelatin, Isinglass, Super Kleer KC, and Biofine Clear. A good example of how fining agents are used to clarify beer is shown in this video by Don Osborn:

8. Are There Methods of Clarifying Beer During The Brewing Process?

Yes, many of the proteins that cause hazing in beer can be precipitated out by cooling the wort rapidly after boiling using a wort chiller like this one:

Other additives can be used during the boil to help clarify beer as well. These include Irish Moss and Whirlfloc Tablets.

What methods have you found effective in clarifying your home brewed beer?

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5 comments on “8 Things You Should Know About “Cold Crashing” Beer

  • I see no mention of oxidation issues with cold crashing. When the beer in the fermenter cools it will pull in O2 (air lock fluid can get sucked in as well). Do you take any precautions against oxidation when cold crashing? What are your thoughts?

    • GoldPaintedLemons

      January 10, 2016 at 11:48 am

      Oxidation occurs when oxygen is “mixed in” or forced into extended contact. If you’re cold crashing, it’s important to make sure you’ve got plenty of CO2 in the vessel, so if you’re doing it in a keg, make sure you’ve primed it well. In a carboy, all your oxygen would have been pushed out during fermentation… so be careful about tracking to another carboy, i.e. make sure your secondary (if you do that sort of thing ;-)) is going to produce some CO2 (regardless of cold conditioning). Idea is that CO2 is more dense (as well as inert) so with a little time, oxygen will go to top, NOT in contact with your beer. Even if it’s pulled in via an airlock, it will stay above the CO2.

      Airlock fluid will definitely end up in your beer though, so make sure that’s sanitized. A little SanStar will not affect the flavor of your beer, and the oxygen in that little bit of water won’t either.

      In general, racking to secondary is a more dangerous endeavor than this for oxidation and infection, which is why I don’t. I know it’s good practice, but it’s risky if not done at just the right time in fermentation.

  • Jason Chubb Custer Veith

    August 24, 2015 at 12:20 pm

    I sanitize the mouth of the carboy, dry it, and use Cling wrap. I haven’t noticed any ill effect from oxidation.

  • I don’t have an extra fridge, but I got a fermentation bag from more beer. I fill it with 9 gallons of water and wrap it in a heavy bedspread. I can maintain 40 degrees with 1-2 gallons of frozen bottles per 24 hour period. I am pretty happy with that.