Carboy batch size/headspace

[FrizzleFry]

I recently decided to ditch buckets and use only carboys. As to why, might have had something to do with having problems with bucket lids, having one that was hard to get off, then the raised plastic lip on the bucket that you pull down on to get the lid off snapping, cutting my hand, etc.

Anyway I just brewed a hefeweizen and put it in a 5 gallon PET carboy as a primary. Probably a mistake, should have used a 6.. or, maybe foam was going to come out no matter what with a hefe. I initially had a blowout tube connected to the bottom piece of an airlock, but it kept popping out the stopper, so I then just stuck the tube directly in the stopper and that seems to have helped. I guess airlocks are just too restrictive for foam.

Anyway, my question is this: I see recipes all the time with 5.5 or 6.5 gallon batch sizes. Is this extra half gallon because you are expected to leave some in the bottom of your kettle with the cold break proteins, or are people finding they can get the extra half gallon into the carboy without headspace issues, or maybe to reduce oxidation?
What batch size do those of you who use carboys for primary fermenters shoot for?

 

[TAK]

Depends on the style for me. For IPAs, I'm starting to aim for about 6.25 gal post-boil. I siphon out of my kettle into the carboy to leave behind the hops, and also the trub. That gets me about 5.25 in the carboy before my starter volume goes in. I expect to get about 5 gal out post-fermentation.

For pretty much everything else, I transfer trub with less discretion. In those cases I aim for about 5.5 gal post-boil, most of which goes into the carboy. With the trub in the carboy, I still get about 5 gal post-fermentation.

Side note: in not sure if these work on your carboys, but a blowoff tube goes well with these...

http://monsterbrew.com/Prod_UniversalCarboyCap.cfm?gclid=CLDJj-7uxcECFcQ-MgodrHUApQ#

 

[grathan]

You can try some ferm-cap defoamer.
http://www.northernbrewer.com/shop/fermcap-s-1-oz.html


I make a bigger recipe, but it is because I leave gallon or two in the kettle and deal with boil-off.

 

[kornkob]

I know there are folks that get really concerned about the headspace but I've found that in primary its not really that big a problem. Oxy is needed early on and as soon as the yeasts start making CO2, they'll make their own blanket and push the O2 out.

If you're really concerned and you keg, you could always shoot some CO2 in to the carboy after pitching the yeast and/or into any carboy you use for secondary.

/braces for the hordes of headspace haters

 

[revco]

Generally speaking, you want to leave ~1 gallon of head room, sometimes more if you've got a particularly active fermentation should you know it ahead of time. Even with adequate head room, sometimes those little yeasties get pretty active and will try to blow the top. As you found, a blow off tube provides less restrictive flow for any unforseen activity...and is why many of us experienced brewers just do that regardless of the brew. There's nothing inherently wrong with using a smaller carboy, other than you lose a bit of beer to the blow off.

The primary loss from kettle to fermenter comes post-fermentation where some of the beer just can't be siphoned out without getting a big portion of yeast. Or you might have some loss due to dry hopping, or gravity checks. The batch sizes you're seeing are usually optimized for trying to get an actual 5 gallons of finished beer from a 5.5 gallon batch. 6.5 would probably be for a desired 6 gallon batch. Hope that helps clarify!

 

[duboman]

You should be using a 6 gallon carboy for 5 gallon batches and you can shoot for 5.5 into primary to get 5 gallons to package final volume.

Headspace in primary is only a concern regarding blow off as with less room you'll have a lot more blow off material. a 5 gallon carboy for a 5 gallon batch is just too small.

 

[thekraken]

You should be using a 6 gallon carboy for 5 gallon batches and you can shoot for 5.5 into primary to get 5 gallons to package final volume.

Headspace in primary is only a concern regarding blow off as with less room you'll have a lot more blow off material. a 5 gallon carboy for a 5 gallon batch is just too small.

I'm about to brew the NB Caribou Slobber, 1.052 og. If my only option at the moment is a 5 gallon carboy, how much beer should I expect to lose through blow-off?

 

[duboman]

I'm about to brew the NB Caribou Slobber, 1.052 og. If my only option at the moment is a 5 gallon carboy, how much beer should I expect to lose through blow-off?

You'll definietly want a blow off tube, not just an airlock! As for loss, I would expect between blow off and trub at least 1/2 gallon. The blow off will be mostly krausen and yeast.

 

[thekraken]

You'll definietly want a blow off tube, not just an airlock! As for loss, I would expect between blow off and trub at least 1/2 gallon. The blow off will be mostly krausen and yeast.

Okay, so I wont actually lose beer through blow-off? I'll lose the same amount of beer as I would if I fermented in a 6.5g bucket?

 

[duboman]

Okay, so I wont actually lose beer through blow-off? I'll lose the same amount of beer as I would if I fermented in a 6.5g bucket?

It's possible you might lose a bit of beer if you have a vigorous fermentation but most will be lost to trub.

 

[fuelish]

When I use a blowoff tube, it's the big honkin' tube that stuffs in the mouth of the carboy itself....have seen thinner tubes rigged to airlock clog and pop out....I don't fret over the lil bit that gets pushed out the tube, just part of the game....no cryin' over spilt milk or blownoff beer