Making an IPA with an OG of 1.069, we pitched at 70°F with good ol' Safale US-05, just dry out of the packet as I've always done with US-05 with good success (I tend to trust it a little too much perhaps). Should have rehydrated probably, but eh, the yeasties got into the bucket. This is my 6th brew so by no means am I an expert.

Day 1 was fine: no activity until the afternoon (T+18h) when it started bubbling lightly as expected.

Night of Day 1 (T+24h - 36h) my roommate (who I brew with and should know better ;)) turned off the A/C in the apartment, so ambient temps rose to about 76°. I checked the temp and the fermenter reached 81°... yikes (IR thermometer and stuck-to-side-of-fermenter thermometer agreed). Bubbler was still going crazy at about 1/second, so I'm guessing that fermentation just took off overnight.

I didn't want the temps up there, so I made a water bath in a rubbermaid bin, with about 68° water, and stuck the fermenter in (submerged about halfway up the bucket). Temps equalized very slowly over about 6 hours and finally stabilized at 72°, which to me seems perfect for this yeast, still even a little high but (I hope) better than it was.

Day 3 and 4 now bubbling slowed and then stopped completely. I haven't opened the lid to check krausen or take a gravity reading yet.

Questions in convenient numbered form:

  1. Could dropping the temperature from that 80° point down to 72° in about 6 hours have "shocked" the yeast in some way?
  2. Is this just the US-05 going through all the sugars in one night like the good little workhorse it is? Only a gravity reading will tell...
  3. Would it be worth re-pitching in case something bad did happen?

Any insights/advice here would be much appreciated!

Obviously going to place the next batch in a water bath from the get go to try to keep things more stable, especially as the summer approaches.

  • 2
    This is a well written question, but it would have probably been quicker to take a gravity reading and know for sure!
    – mdma
    May 10, 2013 at 16:53

1 Answer 1


Don't worry have a homebrew.

  1. It is very unlikely that a temperature change from 80-72 would shock the yeast. People like to ferment at lower temperatures because it produces less byproducts that add off flavors to beer. Additionally, 6 hours for the temperature change is definitely not a quick temperature change in the time scale of yeast.

  2. Agreed only a gravity reading will tell. But one thing to keep in mind is that because of the higher temperature that fermentation proceeded at you will want to let this beer condition for a while most likely. You can figure that out by tasting a sample to see if you have fusel alcohols or estery compounds in the beer. Estery compounds would be changed into better tasting compounds by the yeast while the fusel alcohols will just take time to degrade to less off tasting compounds.

  3. Take a gravity reading. Then decide. Most likely you will be fairly close to the estimated final gravity and you can just transfer to secondary or let is sit on in primary for a while and let it attenuate further. If it is indeed a stuck fermentation then go ahead and re-pitch. But most likely everything is fine but the gravity reading will say for sure.

A water bath is a very good idea for summer brewing in the heat. People also use towels to wick water up and around the whole fermenter. Also if the temperature get way up there you can freeze water in 2 liter coke bottles (make sure to leave a little head space!) and then put those in the water bath to lower the temperature even more.

  • Great advice overall, thanks. I did take gravity and it was indeed close to finished at 1.014. An extra 5 days only brought it to 1.013 and bottled after that... at bottling it didn't taste bad, the malt character came through but there were esters on top. It didn't taste too "hot" or fusel-y (and I know how that tastes since a Belgian we did last time definitely had the same problem, but had aged out well). Unfortunately aging isn't a good option—it's a dry-hopped IPA. We'll see how the esters add to the character :) Sorry for rambling.
    – xxx
    May 18, 2013 at 14:51
  • There are belgian type IPAs which have estery profiles. They are pretty nice, just depends on whether they clash tastewise with your hop choice. Good luck! May 20, 2013 at 16:57

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