Cold Crash

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RE: Cold Crash

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Cold Crashing

Why It's Done

To allow yeast and other matter to settle out
To improve flavor
To precipitate chill haze
To help prevent oxidation

When It's Done

After fermentation has finished
Usually also after diacetyl rest
If you crash the beer too early, the yeast will become inactive (below 40°F) and won't reabsorb fermentation byproducts like diacetyl. Additionally, if you crash while the yeast are still finishing fermentation, they will excrete more ester compounds.

Cooling Rate and Time

Traditional lagering uses a rate of cooling between 1°F and 2°F per day.
The beer is then racked into a closed lagering tank for carbonation.
If fermentation is finished, and the yeast have had time to reabsorb any off-flavors, you can crash much more quickly.
Several weeks is typical, although each batch can vary. Stronger beers tend to need more time.

Temperature Ranges

Yeast activity continues above 40°F, so if yeast action is required, a rest period in the 50°F - 55°F range is recommended.
If no yeast activity is necessary, temperatures can be brought down to near-freezing.
The actual temperature chosen will often depend on equipment limitations. For instance, if your temperature controller has a variance of 5°F, you wouldn't want the temperature setpoint to be 34°F, as the beer may freeze. Likewise, many homebrewers don't have dedicated equipment to achieve these temperatures, but may have a cool basement where cold conditioning can take place