Hot answers tagged temperature
Since there is really no fermentation going on in secondary, temperature is of little concern. as log as you don't get too hot, not much else matters. In fact, there's seldom a need to do a secondary at all.
You wouldn't want a sudden drop in temperature, or too low (8C is way too low), the yeast might give up completely instead of helping the beer mature. 20C should be no problem, the yeast shouldn't be making any esters at this stage. It's also the preferred temperature for the early stage of bottle conditioning. This all assumes you're using a common ale ...
A high gravity beer (high ABV) can take more than a month to carbonate at 70 degrees and if you let it get too cold it may never get to where you want it
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