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Lager vacuum

So I have my first lager, a schwarzbier, in a better bottle in a fridge at about 35 degrees. I didn’t realize it created a vacuum as it cooled down; the bottle is caving in. Luckily I used a silicone flapper type fermentation lock so there’s no liquid to get sucked into the beer, but if I lift the flap to relieve the pressure it will suck in air with oxygen that I don’t want. I’ve never read about this issue with lagers, is it normal?

happens a lot, but more often it seems that people with blow off tubes find that there is not longer any sanitized water left…that it got sucked into their beer

you could lift the flap and blow co2 in there, i doubt the half second oxygen gets in will be a problem

Yikes, at least I wasn’t using that setup! Is there something I did wrong or is this just a common phenomenon? Does it happen every time? In the future I’ll just lager in a keg.

What I have done is pick a day when I will be home for a long time and after putting it in the fridge, go down every hour or two and just crack the seal to let a little air in at a time. If you wanted to be anal you could sanitize a cloth and cover the opening when you did that.

I get the suck-back when I crash cool my beer as well, but I have sanitizer in my airlock, so there’s never an issue, beer has always been as it should be.

No issues with oxydized flavors with this? I’m concerned with post ferment oxygen in the air…

I certainly did not have detectable issues. You are just releasing the vacuum, not shaking it up and I keep the air lock on afterwards. Not sure how else you would do it. The water condenses as it cools creating a vacuum that needs to be released. Mine was in a better bottle and when this happened the first time, when I saw it, it looked like a pretzel. Weakened the BB in several spots.

By periodically allowing the air to equalize while it cools, I am not sure you are actually allowing air to “suck” in. But then, I suck at all the scientific aspects of understanding how gases and liquids work.

[quote=“560sdl”]I certainly did not have detectable issues. You are just releasing the vacuum, not shaking it up and I keep the air lock on afterwards. Not sure how else you would do it. The water condenses as it cools creating a vacuum that needs to be released. Mine was in a better bottle and when this happened the first time, when I saw it, it looked like a pretzel. Weakened the BB in several spots.

By periodically allowing the air to equalize while it cools, I am not sure you are actually allowing air to “suck” in. But then, I suck at all the scientific aspects of understanding how gases and liquids work.[/quote]

When you release the vacuum you are allowing air into the system (vacuums suck). After that, if you are worried about oxidation, push the air back out by refilling the carboy with co2

I guess my point was to not let it get to the point where a vacuum exists. Guess you could argue that air still gets in.

Next time try chilling the wort below the fermentation temperature before pitching. Then rack to a cornie keg or other pressurizable vessel for secondary and pump a CO2 head on it (with O2 being pushed out in the process) before dropping the temperature.

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