Sealed Fermentation

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Meatymc
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Sealed Fermentation

Post by Meatymc » Wed Nov 14, 2018 1:15 pm

I had a day to myself a week or so ago so did a couple of simple bitters one after the other to build up some stock - BIAB and no chill. Only have space for 1 fermenter in the (temp controlled) brew fridge so 1st in there and the 2nd, a few days later, in the utility with a couple of towels wrapped around. I don't normally bother with airlocks but as this 2nd one was sat on a work surface and the wifes constantly in and out of there with washing etc, thought it might be better with one on.

So here's the point .....

1st brew hit all targets and behaved as expected but the 2nd went mental! Krausen bursting through the airlock (there was a good 6 inch of headroom in the fermenter) and down to 1008 after less than 3 days - it's only slowed to a bubble a minute a further 3 days on and still noticeable activity in a scavenged yeast sample I took on day 2. The 1st brew finished at 1010 after 7 days as expected.

The only difference between the 2 is a 4 day time-lag between the boil and pitching the 2nd brew - and of course the fact it wasn't temperature controlled in the utility. Everything else was exactly the same - water treatment, grain, hops, yeast.

Is this just a one-off?

gobuchul
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Re: Sealed Fermentation

Post by gobuchul » Wed Nov 14, 2018 1:44 pm

My guess would be that it fermented more vigorously at a higher temperature. The process of fermenting generates heat, so if it was well insulated, then it would of got quite warm, fermented faster and generated more heat. A bit of a chain reaction.

Meatymc
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Re: Sealed Fermentation

Post by Meatymc » Wed Nov 14, 2018 2:25 pm

Possible I suppose. Although the boiler is nearby we only use that for hot water - we use a log burner for heating. I'd be surprised if the ambient temp is above 18C just because of the towels but could be.

Hoping to have another free day on Saturday so am going to repeat the exercise (and will monitor the temp on the 2nd fermenter) although better check I've enough bottles available to do another 10 gallons.

Gearing myself up to do a couple of back-to-back pilsners and kolschs in the New Year. At least this seems to show I don't have to worry too much about tying up the brew fridge for long periods and can potentially brew bitters/IPA's the old way at the same time.

gobuchul
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Re: Sealed Fermentation

Post by gobuchul » Wed Nov 14, 2018 3:05 pm

I'd be surprised if the ambient temp is above 18C just because of the towels but could be.
Some good information here

https://byo.com/article/controlling-fer ... niques/
Also keep in mind that the heat generated by an active fermentation can warm a typical 5-gallon (19-L) batch of beer by 10 to 15 degrees Fahrenheit (5.5 to 8.3 degrees Celsius).
It could of easily raised the temperature of your brew up into the 20's, if it's around 18c ambient.

Meatymc
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Re: Sealed Fermentation

Post by Meatymc » Wed Nov 14, 2018 3:37 pm

Interesting stuff. In that case, I'll defo do a repeat exercise and carefully monitor the temp on the non-controlled fermenter. Will report back.

gobuchul
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Re: Sealed Fermentation

Post by gobuchul » Wed Nov 14, 2018 4:33 pm

Is your brew fridge in the same room? Keep an eye on what it's doing, wouldn't be surprised if it's doing more cooling than heating if the ambient temp is about 18C. The wort will be heating the fridge up.

Meatymc
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Re: Sealed Fermentation

Post by Meatymc » Thu Nov 15, 2018 11:02 am

gobuchul wrote:
Wed Nov 14, 2018 4:33 pm
Is your brew fridge in the same room? Keep an eye on what it's doing, wouldn't be surprised if it's doing more cooling than heating if the ambient temp is about 18C. The wort will be heating the fridge up.
Yes it is. Going to check ambient temp in the fridge at least every day on this next batch. If it is cooling more than expected and the non-fridge brew is warming up due to activity (was at 17C last night but fermentation has practically finished) this double whammy could well be the explanation.

Of course, the final test on this is how the final brews compare taste-wise when ready

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Kev888
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Re: Sealed Fermentation

Post by Kev888 » Thu Nov 15, 2018 6:20 pm

My guess would be mainly temperature too. Even though the days are getting cooler, my batch of last week needed lots of cooling at its peak - I know because I've a fairly audible fan that kicks in when this happens. Warming wasn't needed until it had largely subsided.

Though there is another possible contributor. In some cases the containment caused by a sealed lid with an airlock can allow the krausen to grow bigger than when it is able to breathe more freely.
Kev

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