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Oxygen intake when cold crash primary

What are you guys doing to limit the amount of O2 getting sucked back in when cold crashing? I’m looking to cold crash and fine with gelatine in the primary. If I did it in the keg I would just purge the keg and set a small amount of head pressure before disconnecting it.

I have the Anvil fermenting buckets… I have rigged it up to have a valve instead of airlocks… With that I can put in a small amount of CO2… About 5 PSI and it leaks out from the lid… I feel good that I have a “minimal” amount of O2 intake… I could be a bit busy and shoot more in a couple times a day until it stabilizes…
Have you checked out the Blulloon? Sneezles61

Yes I’ve seen the balloon idea. Not sure how easy it would be to pull off.

I think you put it on when the fermenting slows… It captures the CO2… when It chills, it sucks the CO2 back…
I’d do your best to minimize the in take… I wonder how the big shooters do this? Do they rack out of the fermenter, into a brightening tank and add CO2 as they chill? Its a process that really needs to be explored for home brewers… Sneezles61

I like the balloon idea I usually just seal it.

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Did look at that as well. Not a bad idea

I usually just cold crash in the keg with the same method. Give it a couple of shots of CO2 and release to purge and seal it with another shot.

When crashing in a carboy I just used plastic wrap and a rubber band or aluminum foil. With the plastic wrap, it would get sucked in a little. With the foil I assume some air got in. I’m not sure at that stage the small amount of air would make any noticeable difference.

I have heard stories about farmers back in the day using a balloon on carboys of hard cider. When it burst, the cider was done.

Maybe nothing noticeable short term but any cold side oxidation can cause issues over time.


You are right MHall… Since I stepped up to 10 gallon batches, O2 “was” more prevalent in the 2nd keg than the first one… Since I’ve been doing my racking with CO2, it hasn’t been an issue. Sneezles61

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Someone out there sells a Co2 capture airlock, which is basically some expensive SS lids for two mason jars in a series. A savvy homebrewer could easily DIY.

Not a big believer in Gelatine.
If you condition under low temp, you don’t need it.

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I agree Tom. Good process and a little patience and you can do without the animal by products in your beer.

Why is that?

If you’re fermenting in carboys just use 3 piece airlocks and you shouldn’t have an issue. If you’re using buckets you’d be better served to cold crash in the keg.

My beers go straight from the fermenter (bucket) to a CO2 purged keg, more CO2, then into the chest freezer for cold conditioning unless they’re getting dry hopped at room temp for a few days first. They’re usually clear by the time they’re ready to serve so I don’t find that any post fermentation fining is necessary.


If we are thinking of the same one its NorCal (brewing solutions)

Well I decided that next batch I’ll worry about oxygen getting sucked back into beer during cold crash. Or I’ll rack to keg and crash. As stupid as it sounds I just purged my chest freezer with some CO2. I didnt go crazy but I figured when the lid stays closed during active fermentation and I stick my head down inside I can tell its building up in there.

I got too much O2 into the kegs… The first one went without too much staling… The 2nd one sat long enough you could tell it wasn’t right… But I’d choke it down… Thats exactly why I soldiered the spuds on my fermenters… I could then eliminate some if not almost all the CO2 whilst cold crashing… Its a process you have think through for yourself… To me, its worked fine. Now to zero in a few other ideas to see what I get… Sneezles61


It doesn’t sound stupid at all to me. Whatever might improve your beer is cool.

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Bumping this thread from @mhall2013 because it is an issue with big west coast and especially NEIPAs. Double dry hopped beers with a fair amount of hop material from brew day and dry hopping creating haze and worse, potentially complicating transfer either from auto siphon clogging or during closed transfer(my current concern).

Haze is fine with NEIPAs but clogged Siphons are not.

My big west coasters are a challenge to rack and I’m looking at cold crashing with ideas to prevent suck back of O2 and or starsan.

Anybody doing anything here?

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