How much headspace is too much?

[wickerman]

I'm just getting into making wild brews and wanted to know how much headspace is too much? I have 4 gals of a braggot of sorts in a 6 gal carboy that I added brett C to about a week ago. My plan was to add 1 gal cherry juice to it at some point down the line, so I'd have 5 gals and still have some room for new fermentation activity. If I don't open it at all, will it be a problem? Maybe I should just fill it up with water and honey to just below the top to be safe?
Any input is appreciated.
Thanks,
wickerman

 

[Hresvelgr]

If you keep a tight bung with a filled airlock you shouldn't have any issues. The CO2 will push outward until CO2 development ceases at that point you still have an air tight seal thanks to your airlock.

 

[sweetcell]

if primary is done, i wouldn't worry too much about needing headspace for a secondary fermentation caused by the cherry juice. if you have a 5 gal fermenter, i would transfer to that.

on the upside, you've got brett in there. that definitely helps with oxidation concerns.

what's the ABV of your braggot?

 

[wickerman]

My thinking is the same as Hresvelgr's, but I don't know if it is right. I've been reading that the bung seal is not totally air tight, and that's my concern.
ABV should be around 5-6%. It was a bit of an experiment I did with a couple gallons of a grain "tea" (steeped like for an extract brew), and around 1lb honey per gallon.

 

[ChugachBrewing]

If you keep a tight bung with a filled airlock you shouldn't have any issues. The CO2 will push outward until CO2 development ceases at that point you still have an air tight seal thanks to your airlock.

Not true, sorry to say. I wish it were. The bungs are not tight at all, some are quite bad actually.
http://www.parc.com/about/people/5/raj-apte.html

 

[dantheman13]

Zainasheff says to fill the carboy as full as possible with as little head space as possible. Tonsmeier says not to worry about it and that he's never had a problem with too much headspace. My experience says that Tonsmeier is correct, but logic leans towards Zainasheff... I try to fill the fermenter as full as possible just to be on the safe side, but if it doesn't work out that way then no big deal (hopefully).

 

[Hresvelgr]

My thinking is the same as Hresvelgr's, but I don't know if it is right. I've been reading that the bung seal is not totally air tight, and that's my concern.
ABV should be around 5-6%. It was a bit of an experiment I did with a couple gallons of a grain "tea" (steeped like for an extract brew), and around 1lb honey per gallon.

I was doing a little looking around and this is a neat idea if you are worried:

https://www.homebrewtalk.com/f163/too-much-head-space-secondary-carboy-316272/

Also, if you look at the specific gravity of CO2 it is heavier than air, so you shouldn't really have too much a problem because the CO2 will create a "guard" against the atmosphere.

 

[Hresvelgr]

My thinking is the same as Hresvelgr's, but I don't know if it is right. I've been reading that the bung seal is not totally air tight, and that's my concern.
ABV should be around 5-6%. It was a bit of an experiment I did with a couple gallons of a grain "tea" (steeped like for an extract brew), and around 1lb honey per gallon.

Not true, sorry to say. I wish it were. The bungs are not tight at all, some are quite bad actually.
http://www.parc.com/about/people/5/raj-apte.html

Thanks for showing this. I was kind of along the lines of "assumption" when I posted that, but I can get on board with what you are saying too. I was kind of relying on the fact that the specific gravity of CO2 is heavier than air which will also help keep the air out of the carboy even after production ends.

 

[dantheman13]

Thanks for showing this. I was kind of along the lines of "assumption" when I posted that, but I can get on board with what you are saying too. I was kind of relying on the fact that the specific gravity of CO2 is heavier than air which will also help keep the air out of the carboy even after production ends.

I'm not sure of the science behind it, but you can't rely on the CO2 blanket for extended aging. Eventually the gases will mix. I've had sour beer get extremely oxidized when my airlock went dry for an unknown amount of time. The CO2 blanket didn't save it, and unfortunately it didn't have a pellicle to save it either.

 

[Hresvelgr]

I'm not sure of the science behind it, but you can't rely on the CO2 blanket for extended aging. Eventually the gases will mix. I've had sour beer get extremely oxidized when my airlock went dry for an unknown amount of time. The CO2 blanket didn't save it, and unfortunately it didn't have a pellicle to save it either.

Good to know!

 

[wickerman]

Thanks for all the information. What is an appropriate amount of head space? Most the pictures in the Pellicle Photo Collection have a good bit of empty head space. Also, if using fruit or juice, do you rack to a larger carboy?
Thanks,
wickerman

 

[Hresvelgr]

I'd say you could use the same size carboy depending on the amount of beer you have. You will have some loss to trub when racking into fruit.

 

[sweetcell]

What is an appropriate amount of head space? Most the pictures in the Pellicle Photo Collection have a good bit of empty head space.

good question. i don't believe there is a one-size-fits-all answer. *personally*, i try to limit head space when aging any beer, sour or not. i'm not a big fan of acetic, which is the main thing that O2 brings to the party. I don't know of anything positive that a lot of head space brings, and i can think of at least one big negative... so i avoid it. no reason for it. i plan my brews accordingly (and have a number of half and one gallon jugs for the instances where i have more than i can fit in long-term aging vessels).

there are plenty of folks brewing good sours with head space in their fermenters so it can't be all bad.

Also, if using fruit or juice, do you rack to a larger carboy?

depends on how much fruit and/or juice you're adding, and how much head space you currently have.

 

[ChugachBrewing]

Wild brews also states that an added 'blanket of Co2" can last weeks, if not a month or two at a time. I have occasionally taken the bung out of a barrel, flooded it with co2, and replaced the bung out of paranoia. the same could be done to a carboy or similar.

the method i've done lately is to use a keg for long sour fermentation where i fear 02. If i notice a beer tasting to acetic, then i rack it to stainless, gas it, and let it be, occasionally purging as fermentation continues.