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I am brewing for the first time. It is a Chinook IPA. The yeast that came with the kit is Safale US-05. I brewed and pitched it on July 4th in the afternoon. The primary fermentation time is 2 weeks as per instructions.

Though the instructions have a temperature range mentioned against the yeast - I didn't realize that this is the ambient temperature range I need to maintain while fermentation takes place. I learnt later in the night that it's better to maintain a temperature between 62F and 70F and anything above 72 risks esters and off flavors. I checked the fermometer on the side of carboy in the night and it read 76F-78F. Yikes! I immediately wrapped a couple of wet shirts around the carboy and turned up my AC and that brought it down to 74-75. Then I ordered an insulation bag for the carboy into which I can put ice packs and bottles that will bring the temperature down to range I need. The bag won't arrive till tomorrow - July 6th. My question is- 1) when is the most important time for fermentation? Am I already too late? I already have a thick Krausen within 18 hours of pitching.

2) will bringing the temperature down now control the hot alcohol / off flavors?

Also, I didn't check the temperature when I pitched the yeast. I'm quite sure it wasnt too warm because I had cooled my wort down in a water bath and added cold water to the carboy + cold water on top to bring the water level up - the tap water is quite cold even in summer where I live. I have a robust fermentation going with constant bubbles in the airlock and a 1.5 inch krausen already.

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It sounds like it was warm in growth phase which is the time esters are mostly produced. This is bad but may not be too terrible at this point.

High heat during feeding phase (where your at now) will produce fusel alcohols ranging from a little more heat in mouth feel to smelling like paint thinner.

What now? Try to keep it in the recommended temp range untill fermentation is almost done. Once the krausen has fallen back in and your within .005 points of of FG. Then get it warm even a couple degrees above recommended temp. This will make it easier for the yeast to clean up the esters produced in growth phase.

Hope this helps.

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  • that sounds right - I was just reading this : byo.com/mead/item/635-fermentation-time-line . What surprises me is that it went into growth phase within 12 hours of pitching - or maybe I am mistaken - it's not in the growth phase yet.
    – vagabond
    Commented Jul 5, 2017 at 16:00
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    @vagabond you probably hit high krausen (feeding phase, "took off") in 12 hours. Which means the growth phase wasn't very long at all. Typical of a proper pitch or over pitch.
    – Evil Zymurgist
    Commented Jul 5, 2017 at 16:23
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The most "important" time for fermentation is probably while it is happening. The yeast produces and consumes things over the course of the fermenting so IMHO their is no particular "important" point per se. The first few days are often considered "important" because (given the right conditions) a lot of of the fermentation can take place then. Some brewers advise that some beers are completely fermented in 4 days. Others often wait a bit longer (I myself prefer to wait 14 days before racking). It also depends on the amount of yeast pitched and the amount of wort aeration/oxygenation. Yeast tends to "grow" in the presence of oxygen and produces alcohol when there is no (or very little) oxygen present. If there is only a little yeast present (ie. the brew is under pitched) then the fermentation will tend to take longer. In such a case the first few days are not so critical. However fermenting for any prolonged time (over a day?) at higher temperatures will usually have an effect on flavour. Not necessarily a bad one - but a different one. This is usually subtle unless a long time is spent at higher temps.

Cooling the fermentation after 2 days at higher temps will IMHO help lower ester production and stop the brew becoming "very fruity".

IMHO the beer should be allowed to continue fermenting and then bottled. I would presume (all other things being equal) that after a month or two in the bottle (conditioning/ageing) it will be fine.

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  • There was a lot of oxygen since I did a half-batch. The carboy is 6 gallons - and i've been getting bubbles almost continuously now in my airlock. Also, I used the entire packet of yeast for the half batch since that's what I read - use all ingredients in half proportion except the yeast. Does this mean the yeast is going to grow rapidly - consume all oxygen and start producing alcohol very soon?
    – vagabond
    Commented Jul 5, 2017 at 15:52
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    @vagabond it's producing alcohol now. CO2 and ethanol are produced at the same time. So if you have co2, you have alcohol.
    – Evil Zymurgist
    Commented Jul 5, 2017 at 16:26
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Agreed. You have little to worry about. Furthermore, Safale US-05 is an outstanding yeast with high tolerance for warmer temps. And because you did not hydrate the yeast first (or did not reveal you did) that delays the first phase of yeast fermentation. I live in very hot temps and often do ales with 05 at 76-78 through the entire fermentation no problem. It is my favorite clean ale yeast. You're fine.

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