cold crash + adding co2 to fermenter

[ChucknBeer]

I have been thinking on "injecting" CO2 to my fermenter (bucket) while coldcrash, to avoid suckback and preventing oxygen from getting to the beer.

I believe that those 12gr catridges plus something like a bike pump connected to a food grade tubing (poor guy solution) or a CO2 charger for kegs... all sanitized, would be enough.

The bucket is not 100% airtight, but the seal is quite good on it, the idea would be to inject CO2 when the airlock shows signs of suckback and until bubbles start going out again, repeating until final temp is reached.

What do you think?

 

[MagicMatt]

Sounds like a lot of work for what you're trying to achieve (minimizing oxidation), as those CO2 chargers need to be manually triggered (if I'm thinking of the small bike-tire ones).

You could theoretically hook up your normal CO2 tank and regulator to the airlock hole and keep a steady pressure of 1-2 psi or so, but there are a couple of issues to be concerned with:

- If you're using a bucket, you'll likely be bleeding a constant stream of CO2 since the bucket is not completely air tight.
- If you're using a carboy, I'd be worried about applying more than 1psi or so of positive pressure to the glass.


There are other ways to minimize oxidation though. You can thwart any air getting in by simply putting a balloon or rubber glove over the opening. When the pressure decreases, it'll just suck the balloon/glove in a bit.

I usually cap my carboys with a solid bung when cold crashing, thus not allowing any air whatsoever to get sucked into the head space. This creates a nice negative pressure (of which I'm still a bit concerned on the effects and stress put on the glass, but alas I've yet to have a problem). You can easily connect a shutoff valve to a piece of hose to stop the air flow in either direction, and then when you're ready to transfer simply hook up the CO2 and open the valve, letting pure CO2 flow into the carboy until equilibrium is reached.

I've also seen people create a 'holding tank' where they actually collect the CO2 put off by fermentation. Basically it's a dry blow-off, if that makes sense. Thus, when the temp drops and there is suck back, it's just sucking it's own CO2.

 

[iijakii]

I usually cap my carboys with a solid bung when cold crashing, thus not allowing any air whatsoever to get sucked into the head space. This creates a nice negative pressure (of which I'm still a bit concerned on the effects and stress put on the glass, but alas I've yet to have a problem).

That's just temporarily delaying it. The second you take off the bung air is rushing in from the negative pressure. I've tried that before and quite audibly heard the rush and saw the beer splash from all of the air rushing in. There's no way to prevent it besides adding CO2 or just not coldcrashing until kegged.

OP, it'd work but by not having a good seal on the bucket you're going to be blowing through a lot of CO2 I imagine. If you did it with a carboy it'd be a lot better. I'd also get a full size CO2 tank, regulator and just set it to 1-2 PSI. Those cartridges add up quickly.

 

[MagicMatt]

That's just temporarily delaying it. The second you take off the bung air is rushing in from the negative pressure. I've tried that before and quite audibly heard the rush and saw the beer splash from all of the air rushing in. There's no way to prevent it besides adding CO2 or just not coldcrashing until kegged.

OP, it'd work but by not having a good seal on the bucket you're going to be blowing through a lot of CO2 I imagine. If you did it with a carboy it'd be a lot better. I'd also get a full size CO2 tank, regulator and just set it to 1-2 PSI. Those cartridges add up quickly.

Think you missed the part with the ball valve connected to tubing, connected to the bung. So it's 'solid' while crashing, then I hook up my CO2 line to the ball valve and open it until the pressure stabilizes. Thus, only CO2 gets in.

 

[iijakii]

Think you missed the part with the ball valve connected to tubing, connected to the bung. So it's 'solid' while crashing, then I hook up my CO2 line to the ball valve and open it until the pressure stabilizes. Thus, only CO2 gets in.

It appears I misunderstood

 

[MagicMatt]

Another idea I've had but have yet to try is to inflate a balloon with CO2 and secure it over the carboy. There would be enough air in the balloon so that once attached, there would still be a good volume of CO2 left in the balloon after the head space pressure has equalized. Eventually as the pressure dropped, it would suck the air from the ballon into the carboy. The goal would be to have enough CO2 in the balloon to keep positive pressure on the beer the entire time.

The logistics of this is the main reason I've yet to try.

Edit: Lightning just struck. Why not put an empty balloon on the carboy during the last couple of days of active fermentation? This would allow you to collect the expelling CO2 and then when you cold crash, it would just get sucked back in. I think I'm going to have to try this with my stout in primary.

 

[iijakii]

Yeah I've seen someone do that before here on HBT. Fill a balloon up with CO2 and then rubberband it over the neck of the carboy.

One of the math wizards like dougcz should calculate how much volume shrinkage there is in a typical carboy and how much CO2 you need there. Of course with gas compression that'd be a hard thing to quantify into a balloon.

 

[MagicMatt]

One of the math wizards like dougcz should calculate how much volume shrinkage there is in a typical carboy and how much CO2 you need there. Of course with gas compression that'd be a hard thing to quantify into a balloon.

<--- Math Wizard :rockin: (not to knock dougcz et al)

Though I lean more towards calculus, probability, and statistics. Fluid and air dynamics have never been my strong points, but it's something I'm definitely interested in advancing.

Any rate, without digging for formulas, I'd imagine it'd be pretty easy to gauge the volume needed in the balloon by simply doing a couple of tests. Attach an empty balloon at the beginning of a cold crash, which should suck into the carboy by the end, at which point I could pour water into the inverted balloon to measure the volume. Comparing that with the amount of head space initially would give a pretty good indication of the volume needed for subsequent crashes.

From my understanding, while the liquid (beer) would indeed contract a bit with a temp shift, it is mostly the air (head space) contracting that is responsible for the suck back. Seems like a couple of exBEERiments are in order!

 

[kevink]

This is how I do it. It's a low pressure propane regulator that provides 0.4 psi during the cold crash. It works extremely well. Without a perfectly sealer fermenter, you're screwed. It takes my beer 1 day to go from fermentation temps to cold crash temps. Can you sit by the fermenter for a full day watching the airlock and injecting CO2 when necessary? You need to be able to set it and forget. I thought about using balloons but abandoned the thought when I realized that they are not exactly impermeable. And what if it pops when you're not there? If you want to go with that type of idea, get a Tedlar bag. They're made for collecting air samples for chemical analysis and should not be permeable. Still, though, you're going to need a perfectly sealed fermenter. There's a little more info on my system here:

https://www.homebrewtalk.com/showpost.php?p=7281727&postcount=183

 

[ChucknBeer]

Hi kevin, nice setup!

Yes, I'm aware that it would take a lot of hours of injecting CO2 in order to allow the beer to cool down to coldcrash temps without any oxigen intake... but my idea is to prevent the "big" air suckbacks.

In my experience, leaving the 3 parts airlocks with vodka/whatever installed and then coldcrashing makes the bucket lid to "bend inwards", it looks like at lease some vacum has been created: the lid's seal is not perfect but it must be at least reasonable good. And when you take out the airlock to avoid vodka/whatever to be suck in, the air rushes inside the bucket with a "fshhh" sound.

That's the intake I want to prevent. By adding some CO2 i can at least equalize some of the pressure, eliminating the vacum. It is not perfect, but it must be better than allowing air go in freely, by using the airlock without water/using tinfoil during coldcrash.

 

[drgonzo2k2]

I do the balloon trick, and it works great. You can get 100 of those children's punch balloons (the big ones with the rubber bands) for just a few bucks on Amazon. I ferment with a regular air lock, and then when I'm ready to cold crash I fill a balloon with CO2 from my tank and attach it to the airlock. For my 30L Speidel fermenters I've found if I fill the balloon about halfway full it seems to suck in nearly all of the CO2, and I'm left with a shriveled up balloon at the end of a 2 day cold crash. Then I transfer from my cold fermenter (33F) to my keg, which goes into the keezer at 40F, and I've been getting very clear beer.

Pro tip if you're going to do this - It's much easier if you have some extra airlocks, use a new one, attach the balloon to that, then fill the balloon already attached to the airlock, and then just switch air locks than it is to try to fill a balloon and attach it to the air lock on the fermenter.

 

[AnOldUR]

That's just temporarily delaying it. The second you take off the bung air is rushing in from the negative pressure.

The way I see it, O2 absorption is mostly a matter of time, not an instantaneous thing. Otherwise every glass of beer you drank would taste oxidized. If you transfer to a purged keg right after taking the bung off, O2 absorption should be negligible. If you want to be paranoid, not replacing the beer with CO2 during transfer is a bigger problem. I use CO2 at a super low PSI during transfers. So low that the needle doesn't move, but you can hear a slight hiss when you put your ear to the regulator.

IMO most of these ideas are the proverbial solutions looking for problems.

 

[ChucknBeer]

I do the balloon trick, and it works great. You can get 100 of those children's punch balloons (the big ones with the rubber bands) for just a few bucks on Amazon. I ferment with a regular air lock, and then when I'm ready to cold crash I fill a balloon with CO2 from my tank and attach it to the airlock. For my 30L Speidel fermenters I've found if I fill the balloon about halfway full it seems to suck in nearly all of the CO2, and I'm left with a shriveled up balloon at the end of a 2 day cold crash. Then I transfer from my cold fermenter (33F) to my keg, which goes into the keezer at 40F, and I've been getting very clear beer.

Pro tip if you're going to do this - It's much easier if you have some extra airlocks, use a new one, attach the balloon to that, then fill the balloon already attached to the airlock, and then just switch air locks than it is to try to fill a balloon and attach it to the air lock on the fermenter.

Good idea!