Fermentation freak-out question #4786

Yesterday my brew was fermenting like crazy all day. House about 75 degrees. I had noticed that it was slightly slowing down and settling when I went to bed. I left the windows open and when I woke up this morning, it was sorta chilly in the house...about 65 degrees. Looks like all the matter is settling and not moving around anymore. A few small bubbles here and there.

Do you think the temp change affected it or it do you think it's just running it's course? I pitched the yeast around 10pm Friday night. So by 10pm Saturday night it had already done a somewhat violent fermentation and then began to slow...

If it was fermenting at 75 you will have esters for sure. Yeast dont like a big swing in temp. You committed now so just see how it plays out.

10 degrees in 24 hours is a bit of a temp swing. however, room temp and fermentation vessel temp are two different things.

if you don't have a thermometer/fermometer on your bucket or carboy, get one. the fermenter can be +/-10 degrees than ambient room temp.

you may or may not end up with esters in your beer...depends on the actual beer temp.

if you don't have a thermometer/fermometer on your bucket or carboy, get one. the fermenter can be +/-10 degrees than ambient room temp.

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As an example, I have my fermenter in the garage where the ambient temp is 65º, but by fermometer is showing 72º.

what exactly are esters and what will they cause?

rflem550 said:

what exactly are esters and what will they cause?

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bad stuff, and headaches.
I know..
Ouch.

Esters are the compounds that give fruity tastes, their production is usually increased at high temps but may be produced at lower temps too (depends on the yeast strain). Not necessarily a bad thing in ales even desired in some styles. High temperatures produce fusel (higher) alcohols. These alcohols will give your beer a solvent like taste and they can cause the headaches.

House at 75 with active fermentation is pretty high, but ultimately depends on the yeast strain. Do a search about the ways to cool that down. One way is to put it in water (like in the bath tub), the water can absorb the heat and move it away from the fermenter. Also keeping it in a water bath will prevent huge, fast swings in temperature in the fermenter even if the house temp changes a lot.

Also, a swing of 10 degrees in 24 hours during active fermentation should not hurt the yeast. Double check the recommended temp range for your yeast and make sure that you are reaching the lower limit.

Sounds to me like the high initial temp caused an aggressive fermentation, you may have esthers, you may not, they shouldn't ruin your beer either way so relax.

As for it slowing down, the ferment could just be running its course or the temp change may have slowed things down. Remember, just because the airlock isn't bubbling, that DOES NOT mean fermentation has stopped.

I would say leave it be until 7 days have passed, then take hydrometer readings on consecutive days to determine whether or not the beer is truly finished. Then you can either leave it another 7 days then bottle, or transfer to secondary for additional clearing.