Been playing around with this for a few batches and it works. Fill the bag with co2, attach in place of air lock and the co2 in the bag displaces the head space.
Bottled a couple 5 liter batches today without a hitch. I haven’t tried it on 5 gallon batches yet. Might need to replace bag before end not sure.
here are the bags and the spigots if any one is interested
Could you just attach your CO2 line to the rubber stopper, and slowly (<=1-2psi) do the same thing minus the need for the bag?
Yep. I’ve done that. Sorta where I got the idea looking for better alternatives. The co2 pressure pops the bung out cuasing it to have to be constantly monitored. IN this particular instance I was bottling directly from the fermenter so that definitely wouldn’t work.
Obviously if you have a vessel capable of being and holding pressure a tank of Co2 might be a better solution. Maybe not for bottling though since it puts pressure on the line and forces the beer out faster than you may want it.
Another thing that struck me is that if homewbrewers don’t have co2 they could simply collect the co2 off their fermentation into the bag and use that in place of filling the bag.
Fair enough.
Have you seen an improvement in product, when bottling with CO2 in the headspace, as opposed to standard?
Kinda like the party balloon a lot of people have started using.
That was my thought.
How bout that? Didn’t see the size but same concept.
Actually yeah, 2.5 gallon. This one is 5 gallons and cheaper option
I use Fast Ferments and just stick a plug in the airlock hole when I cold crash, the lid seal & plug hold what little vacuum is created during crashing. As for the bag thing, I’ve been using a supersized balloon of CO2 attached to the airlock when bottling for several years now. Probably accomplishes very little, but almost certainly doesn’t hurt.
I guess it’s a bigger deal for me than it is for others. I never like racking a beer and displacing with air. I much prefer a closed transfer system. The only time I am not closed transfering is when I am bottling and bottle conditioning and even with that I am considering using a CPBF to purge with Co2 first (not filling under pressure).
One of the big benefits is if you are racking and you accidentally screw up your process and bubbled get in the line – that Co2 instead of air.
Another big bonus is the yeast cake is under Co2 instead of unfiltered air (unless you use a filter 
)
FTR you can also purge your racking line if you have a “siphonless fermenter” by having a small amount of Co2 in your keg and attaching the line via a QDC with port “closed” – the Co2 will purge the line pushing the air out that tiny hole that is on every single plastic spigot I have ever encountered (the reason for I have never completely fathomed).
I use that tiny little hole on the spigot to flush it with StarSan. I put a hose on the bottom (output) of the spigot and fill it with StarSan until it starts shooting out the little hole.
Utilizing those hidden options… love it! I believe when the idea struck me me to purge the racking line was when sani left over in the keg shot me in the face out of that little hole (insert joke here)
Great idea! I wonder how this would work as a bladder for collecting co2 during ferment. Wish I could re-cycle all that gas somehow and at least use it for purging a keg of starsan. Tried garbage bags but they are a little too thin for squeezing the gas back into the keg.
That definitely works. I’ve tried it. Great option for those folks who don’t keg or have a Co2 rig. In fact, that got me to thinking that folks who insist on using a “secondary” should attach the “secondary” to the primary with a double hole bung and add the airlock on the “secondary”. That way the “secondary” is purged with co2 (mostly).
I routinely stack up my clean kegs and use the fermenter CO2 to push sanitizer out of the first filled keg to a bucket and then pour into the next keg filling it and repeat. You can also daisy chain them to go with multiple kegs for one fermentation, dropping them out as they become empty. Easy use of CO2 and not wasting it - you could put the airbag in the first spot in line and give it a try.
This is a great idea, and I love the idea of capturing and re-using the CO2 from fermentation.
That said, I do wonder how much O2 is ingressing during an open transfer from fermenter to keg, which is what I do. I use a siphon starter, and the hose is attached to the beer-out connector on closed, purged keg, which is filled until beer spills out of the opened PRV. There’s always at least 1/2 gallon of beer left behind in the fermenter (a 7-gal Fermonster), usually it’s ~3/4 gal.
Oxygen is not very soluble in liquid. In the 15-ish minutes it takes to fill my keg, I doubt enough oxygen has dissolved in the beer to the point where it has seeped below the top ~1 inch of beer in the fermenter. IOW, I doubt that the beer that actually gets into the keg has any oxygen in it due to the open transfer.
My doubts can be easily dispelled by data on oxygen ingress from open transfer, if anyone has any. Otherwise we’re all just speculating, and I’ll choose doing nothing (i.e. the KISS principle) over doing something if I can get away with it, which so far I have been able to.
I agree, it may be overkill. Without any actual testing it is impossible to know if there is any effect of the final DO levels. And this method might be impossible to do with an auto-siphon.
I have been bottle conditioning most of my homebrews for the last couple of months and I am not purging the bottles before filling and I have to admit they are turning out pretty great (for me). And the ones I put in kegs with autosiphon turned out pretty great (for me) as well. So who knows? I may try to test it with a DO meter here in the next couple of months just for grins. It makes me feel better and, since I am lazy, it allows me to harvest the yeast at a later date since I don’t feel there is any risk of added infection with my “kitchen air”. Two great danes and a crazy cat – not the cleanest home ever.
I think a big factor is how long the bottles or keg sit before drinking them. I don’t purge my bottles with CO2, but for the last couple of years I’ve been planning brew days so that I can start drinking a batch when it is carb’d up, rather than brewing ahead. It seems to help a lot in terms of hop aroma. That might be why experiences differ for different brewers. I like a low tech solution.
With hop aroma fresher is always better. And oxidation is a big enemy if you are trying to retain those aromas. I have mostly been brewing German lagers and English style ales at home. Regardless, I think this would work extremely well for hoppy beers. And … uhm, this is an extremely low tech solutions. It’s a collapsable plastic bag.
