[Richard]

Today I was moving a carboy that had been cooled to 34 F for several days, and as I moved it a bit there was gas bubbling out of the airlock. I have noticed on many occasions that fully-fermented but non-carbonated beer has quite a bit of CO2 in solution which will come out if there is a bit of agitation. Usually the concern during cold crashing is that oxygen will be sucked in, and there are various schemes to avoid this.  I wonder if a little bit of jiggling now and then would cause enough CO2 to come out of solution too keep the pressure positive and avoid any suckback. With an S-shaped airlock it is easy to see which side has the higher pressure. This would be a free and easy solution, and it could possibly even be automated. Am I missing something?

[TeeDubb]

It could work in theory as long as there is enough C02 in solution, but requires fussing and attention. There are other simple methods to accomplish the same thing (prevent oxygen intrusion into the fermenter as it cools). I've had good luck purging a balloon with C02 and then tying it to the airlock at the tail end of fermentation.  The balloon fills with C02, then as you crash, the C02 goes back into the fermenter. As long as the airlock is not overfilled, sanitizer should not touch your beer (not that it would do any harm anyway).

[Pope of Dope]

I thought that CO2 was heavier than O2 and sits on the beer like a blanket. I've never, to my knowledge, had an issue of oxidation during cold crash. Are you talking about lagering? I don't know much about that, but never had an issue with my 2-4 days of cold crash.

[Robert]

I thought that CO2 was heavier than O2 and sits on the beer like a blanket. I've never, to my knowledge, had an issue of oxidation during cold crash. Are you talking about lagering? I don't know much about that, but never had an issue with my 2-4 days of cold crash.

Popular misconception about the CO2 "blanket."  CO2 is heavier, but this is irrelevant.   Due to diffusion any assortment of gases very rapidly mix, so CO2 and O2 will both proportionally be in contact with beer.   Nonetheless, I'd think very little air is usually sucked in,  probably pretty far down the list of risks for oxidation in the whole brewing process.

I really like the balloon idea if you want to be safe. (Wish I'd thought of that when I used carboys and s-locks.)  It is indeed a hands off method, unlike jiggling  --  but I bet that would work fine too.  There is a fair bit of CO2 in post fermentation beer fermented at atmospheric pressure, something like 0.75 v/v.  It's going to gas off anyway at its own pace, so you could utilize it.

[kramerog]

I've had good luck purging a balloon with C02 and then tying it to the airlock at the tail end of fermentation.  The balloon fills with C02, then as you crash, the C02 goes back into the fermenter. As long as the airlock is not overfilled, sanitizer should not touch your beer (not that it would do any harm anyway).

What kind of balloon?  Where did you get it from?  I bought some mylar balloons, but they don't fit over the air lock.  I have to tape them onto a hard plastic tube and then replace the airlock with the tube and balloon. I'm cold crashing my second batch with rubber balloons and am not satisfied that I've figured out the best way for me.

[BrewBama]

I believe Bobby at Brewhardware sells a balloon solution. Here are some other ideas: http://brulosophy.com/2018/05/10/7-methods-for-reducing-cold-side-oxidation-when-brewing-beer/


Sent from my iPad using Tapatalk

[denny]

Why use an airlock when you cold crash?  Why not seal the carboy?  I know the standard answer is to prevent pressure from collapsing the carboy, but has anyone ever investigated whether that would really happen?  I'd guess there's not enough pressure.

[lupulus]

Buy a Speidel. You can seal it and plastic will absorb the pressure change.
Beer will oxidize significantly if left exposed to air,  but it is up to each brewer to decide how important this is.

Sent from my SM-G960U using Tapatalk

[TeeDubb]

Early attempts were just a gallon ziplock bag with one of the non-zipper end corners cut off, then zip-tied around the neck of the airlock as it comes out of the stopper. Would purge and fill the bag with C02 right before cold crashing when there was no airlock activity. Later, just bought mylar party balloons at the grocery store and cut the nipple off to fit the airlock. I've seen others just replace the airlock with a short length of straight tube and tape it to the mylar balloon nipple.

[TeeDubb]

Why use an airlock when you cold crash?  Why not seal the carboy?  I know the standard answer is to prevent pressure from collapsing the carboy, but has anyone ever investigated whether that would really happen?  I'd guess there's not enough pressure.

I was thinking that at some point later when the fermenter needs to be emptied, the pressure difference (due to sealed cold crash) would have to be managed somehow without introducing oxygen. Maybe if you have a valve and can manage a careful closed transfer, this is possible. There are many solution to the same challenge!

[denny]

Buy a Speidel. You can seal it and plastic will absorb the pressure change.
Beer will oxidize significantly if left exposed to air,  but it is up to each brewer to decide how important this is.

Sent from my SM-G960U using Tapatalk

Or ferment in a corny

[Richard]

Let me say first that I am not a chemist. When Robert posted something about surfactants I thought he was talking about a Beach Boys movie. 

I estimate that my 2 gallon (7.5 liter) headspace will shrink by 7% when cooled from 70 F (294 K) to 34 F (274 K). That is a volume of about 16 oz (500 ml), not a trivial amount. That air will mix in the headspace, exposing the beer to a 7% air mixture for days. Of course the exposure will be at a low temperature, so the chemical reactions will all be slower. There are other phases of the packaging process where the beer can be exposed to pure air but only for a few seconds or minutes. Which is worse: exposure to 7% air at 34F for days or exposure to 100% air at room temperature for seconds or minutes? I don't know, but my gut tells me that the longer exposure would more than compensate for the reduced temperature and concentration.

Using a rubber balloon should work, provided you put it on at the right time. Too early and it would overfill and explode or blow off. Too late and it would not collect enough CO2 and would collapse during the cold crash. Now I know that if that happens, though, I can just jiggle the carboy to release enough CO2 to partially inflate the balloon again. I will try that experiment on my next batch.

[Robert]

Buy a Speidel. You can seal it and plastic will absorb the pressure change.
Beer will oxidize significantly if left exposed to air,  but it is up to each brewer to decide how important this is.

Sent from my SM-G960U using Tapatalk

Or ferment in a corny

Hmm... think of all the threads where a prospective beginner seeks advice on what kind of gear to buy.  We regularly tell them things like, make sure you get a big enough this or that, 15 gallon kettles, mash tun, electric whatever, BIAB, definitely temperature control right from the start -- wort chiller, ferm chamber... and with all this 21st century advice, get buckets or carboys, they're fine for a start.  Next time there's such a thread, maybe we should think of mentioning the need somehow  to deal with oxygen on the cold side (not touching on HSO here,) which we're all cognizant of now, unlike a few decades ago when the basic beginner's kit was set in stone.  It fits the same theme of "buy once cry once, retain resale value,  and develop good habits from the start."  Just a thought.

[denny]

Buy a Speidel. You can seal it and plastic will absorb the pressure change.
Beer will oxidize significantly if left exposed to air,  but it is up to each brewer to decide how important this is.

Sent from my SM-G960U using Tapatalk

Or ferment in a corny

Hmm... think of all the threads where a prospective beginner seeks advice on what kind of gear to buy.  We regularly tell them things like, make sure you get a big enough this or that, 15 gallon kettles, mash tun, electric whatever, BIAB, definitely temperature control right from the start -- wort chiller, ferm chamber... and with all this 21st century advice, get buckets or carboys, they're fine for a start.  Next time there's such a thread, maybe we should think of mentioning the need somehow  to deal with oxygen on the cold side (not touching on HSO here,) which we're all cognizant of now, unlike a few decades ago when the basic beginner's kit was set in stone.  It fits the same theme of "buy once cry once, retain resale value,  and develop good habits from the start."  Just a thought.

Ya know, I'd say that's way down the list of things a beginner needs to worry about.  And I'm not sure I really agree with the buy once, especially when one of the first things a beginner will use to ferment is a bucket.  They work fine and are inexpensive enough that they can be forgotten it the beginner wants to move on.  One thing that REALLY discourages beginners is being told they need a bunch of equipment when they don't even know if they'll stick with the hobby.

[Robert]

Buy a Speidel. You can seal it and plastic will absorb the pressure change.
Beer will oxidize significantly if left exposed to air,  but it is up to each brewer to decide how important this is.

Sent from my SM-G960U using Tapatalk

Or ferment in a corny

Hmm... think of all the threads where a prospective beginner seeks advice on what kind of gear to buy.  We regularly tell them things like, make sure you get a big enough this or that, 15 gallon kettles, mash tun, electric whatever, BIAB, definitely temperature control right from the start -- wort chiller, ferm chamber... and with all this 21st century advice, get buckets or carboys, they're fine for a start.  Next time there's such a thread, maybe we should think of mentioning the need somehow  to deal with oxygen on the cold side (not touching on HSO here,) which we're all cognizant of now, unlike a few decades ago when the basic beginner's kit was set in stone.  It fits the same theme of "buy once cry once, retain resale value,  and develop good habits from the start."  Just a thought.

Ya know, I'd say that's way down the list of things a beginner needs to worry about.  And I'm not sure I really agree with the buy once, especially when one of the first things a beginner will use to ferment is a bucket.  They work fine and are inexpensive enough that they can be forgotten it the beginner wants to move on.  One thing that REALLY discourages beginners is being told they need a bunch of equipment when they don't even know if they'll stick with the hobby.

Fair enough.   I'm not about to tell them they need all this stuff and scare them off.  Just a lot of us eventually come up against this and put it in the "sure wish I knew about this earlier" file.  Just thinking a quick mention that it might be down the road could help a brewer setting up their first outfit decide how to allocate resources.  At least advising against glass carboys (evil things) is a start.