Small batches in large ferementers - ?

[Crazy Climber]

Brewing 3-gallon (or even 2.5-gallon) batches in a 5-gallon carboy: too much headspace, or perfectly acceptable?

Your thoughts? (Thanks in advance.)

[BlackDuck]

Good question....I've been considering it also. Can't wait for the responses!

[RickBeer]

Everything I've always read is that there is enough CO2 produced in a primary that it doesn't matter. In a secondary, too much headspace could be an issue, but many say it isn't (less CO2 produced).

[gwcr]

Someone can check my logic here, but here's how I think about it.

CO2 is heavier (more dense) than O2. Therefore it settles lower than O2 creating a blanket over the exposed surface area of the wort. For the volumes we are working with, it doesn't really matter how thick that blanket is. The O2 simply won't get through, and the fermentation will still be producing more CO2 anyway. So for me, ferment however much you want in whatever vessel you have.

I agree with RickBeer that it might be a bigger deal in a secondary, but I don't secondary so...

[Chuck N]

I do three gallon batches in a five gallon bucket. I have no problems with it.

[DaYooper]

No problemo with a primary as O2 doesnt matter until after fermentation in which case it will be covered amply by the CO2. If fermentation is still going on when you secondary into a 5'er you shouldnt have any problems either, but just dont wait until it has pretty much stopped unless you do a purge with CO2.

[FrozenInTime]

Ditto, what they said. If I am using a slow to start yeast, I will shoot a small squirt of C02 into the fermenter before putting the bubbler on. Just to protect the wort for a few hours, but I get anal at times. Probably not necessary, but I have it, so I do it. I do smaller batches alot and have never had a problem using the 6 gallon carboy with 3 gallons.

[John Sand]

Thanks guys. I'm thinking of a small batch in the Ale Pail too.

[mashani]

I only fill a fermenter 2/3 full at the most all the time when I'm using 3787 and it's never been a problem. Only way there is to limit blowoff with that yeast.

[Crazy Climber]

If I am using a slow to start yeast, I will shoot a small squirt of C02 into the fermenter before putting the bubbler on.

FIT - how do you do that? What device do you use to "squirt" CO2 into the fermenter?

[DaYooper]

If I am using a slow to start yeast, I will shoot a small squirt of C02 into the fermenter before putting the bubbler on.

FIT - how do you do that? What device do you use to "squirt" CO2 into the fermenter?

It can be as simple as a hookup to the CO2 tank with the other end opened, or a picnic tap hooked up to the tank. As CO2 is heavier than O2, it will blanket the wort. I dont think pre-fermentation it is really an issue as we aerate the wort at that point but I could be wrong. Ive never worried about it unless I have a lot of headspace in the secondary.

[Crazy Climber]

I dont think pre-fermentation it is really an issue as we aerate the wort at that point but I could be wrong. Ive never worried about it unless I have a lot of headspace in the secondary.

Yep, that was my thinking, as well. If I were to pursue CO2 "blanketing," it would only be when racking to a secondary, and even then, only if primary was clearly all done already.
I was wondering if something like thiswould be appropriate for that task.
In all, it's probably more effort than it's worth, but there is a peace-of-mind component to it. Considering that I currently leave beers in LBK's for 3 weeks, which have an open "air lock" up top, I probably shouldn't be too concerned about head space in a proper carboy.

[Inkleg]

Everything I've always read is that there is enough CO2 produced in a primary that it doesn't matter. In a secondary, too much headspace could be an issue, but many say it isn't (less CO2 produced).

^This^

Someone can check my logic here, but here's how I think about it.

CO2 is heavier (more dense) than O2. Therefore it settles lower than O2 creating a blanket over the exposed surface area of the wort.

Check that, your logic is flawed.
The Co2 blanket is a myth, if not we would all be dead from breathing Co2 and not enjoying beer. What will happen is the Co2 will mix with the O2 and most will be expelled with the expanding gas being formed. So there will be far less O2 left in the fermenter.

[zorak1066]

ive brewed 2.5 gallon batches in a 6 gallon bucket with no problem. they arent even air tight if lack of airlock activity is an indication... and no problem.

[DaYooper]

Everything I've always read is that there is enough CO2 produced in a primary that it doesn't matter. In a secondary, too much headspace could be an issue, but many say it isn't (less CO2 produced).

^This^

Someone can check my logic here, but here's how I think about it.

CO2 is heavier (more dense) than O2. Therefore it settles lower than O2 creating a blanket over the exposed surface area of the wort.

Check that, your logic is flawed.
The Co2 blanket is a myth, if not we would all be dead from breathing Co2 and not enjoying beer. What will happen is the Co2 will mix with the O2 and most will be expelled with the expanding gas being formed. So there will be far less O2 left in the fermenter.

I usually purge the secondary prior to even racking.

Interesting reading:
http://colinb-sciencebuzz.blogspot.com/ ... -sink.html

On another note, this is sort of saying that these devices:
http://www.winedevices.com/product-p/77 ... 4_a_7c7760
... are pretty much useless since it relies on a few short burts and the gases resting on the wine and not necessarily purging the bottle.