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Fermenting 1 gal batch in 5 gal carboy

I want to try some experimental 1 gal batches. Can I ferment them in a large carboy or would there be a problem with surface area exposed to air?

Also, for a 1 gal batch wouldn’t you want a fermenter larger than 1 gal to provide room for the head? Where can you get a 2 gal carboy?

Anything less than 3 gallons in a 5 gallon carboy causes a tear in the space time continuum. But really, it’s fine, I’ve done it. The only ill-effect is that one gallon looks pathetic in that big of a container. Other options; 3 gallon carboy, 2 gallon food grade bucket, any thing large enough and clean enough, etc.

:cheers:

MW sells 2 gallon pails. Or check with some of the gas stations that have deli’s and see if they have some pails you can get for free.

You can get one right around the corner from you at NB

http://www.northernbrewer.com/shop/2-ga ... -base.html

[quote=“chuck”]You can get one right around the corner from you at NB

http://www.northernbrewer.com/shop/2-ga ... -base.html[/quote]

$5.99 for the pail. $2.50 for the lid.

http://www.midwestsupplies.com/2-gallon ... d-lid.html

$4.99 pail/lid combo.

Or free pail from a bakery + $.50 grommet.

You’ve suggested an intriguing idea,one which I’ve given thought to myself.But now that you’ve got me thinking about it in this light,I’m inclined to give some serious thought to the whole airspace issue.I can’t help wondering if all that airspace might actually be a bad thing.I mean,the expulsion of carbon dioxide from the wort during fermentation is one of the critical aspects of yeast metabolism,if I’m not mistaken.I might be wording that horribly and misrepresenting the idea I’m trying to get across,but I think you get where I’m going.I’m wondering if the fact that there’s so much airspace between the surface of the wort and the airlock would mean that the carbon dioxide pressure would never be able to gain enough force for it to eject itself out of the fermenter,resulting in the wort reabsorbing an excessive amount of that CO2 (there-I’m sick of typing the whole thing).Then again,such a small amount of wort should really ferment completely in a very short amount of time-I’m thinking 2 days,max.So there’s probably not enough time in that process for that to be an issue.And then again,bottled and kegged beer is always comingling with CO2 until it’s deceanted,and I doubt it’s a problem,but we’re talking about fully fermented beer in that case,not beer that’s still fermenting.I don’t know…maybe I’ve posed a completely stupid question,but I’m curious.This might be a question for BYOB magazine’s Mr.Wizard (or whatever his name is).Carry on.

I think I get where you’re going with this, but I assure you it’s not an issue. On the one extreme, consider closed pressurized fermentation (this is the only way I brew now). With this system, the fermenting beer is always under pressure, therefore it’s absorbing CO2 from the beginning, so by the time primary fermentation is complete, the beer is also fully carbonating which saves you a lot of time and at least one step. Fermenting under pressure has several benefits which is another topic entirely. On the other extreme, consider open fermentation, where there’s no airlock at all, and the fermenting beer is open to the air. This example IMO is closer to the situation above of 1 gallon in a 5 gallon carboy. Again, a totally viable option in brewing.

I think I get where you’re going with this, but I assure you it’s not an issue. On the one extreme, consider closed pressurized fermentation (this is the only way I brew now). With this system, the fermenting beer is always under pressure, therefore it’s absorbing CO2 from the beginning, so by the time primary fermentation is complete, the beer is also fully carbonating which saves you a lot of time and at least one step. Fermenting under pressure has several benefits which is another topic entirely. On the other extreme, consider open fermentation, where there’s no airlock at all, and the fermenting beer is open to the air. This example IMO is closer to the situation above of 1 gallon in a 5 gallon carboy. Again, a totally viable option in brewing.[/quote]

You make some valid points,but I’m not convinced that the open fermentation scenario really is a very close parallel to the scenario we’re talking about here.I think those two situatioins are pretty different.I could be dead wrong,though.I don’t know.

^-- This :wink: . I gave the example of the two extremes to make the point that healthy fermentation occurs under a range of CO2 pressure, and fermenting a small amount of beer in a large vessel is closer on that range to the extreme of open fermentation. Obviously there are a lot of other variables at play when comparing open fermentation vs airlock fermentation vs pressurized fermentation, but what you were concerned about in your post was the absorption of CO2 during that process. On the homebrew scale gas absorption is not significantly influenced by the size of the vessel relative to the volume of fluid (unless of course the gas dispersion is restricted, but even then it becomes an issue of gas pressure, not vessel geometry). While it’s easy to get caught up in the ‘magic’ of brewing, we have to remember that fluid dynamics applied to beer too, and a full vessel is a full vessel, regardless of ratios that fill it. Therefore, 1 gal of beer in a 5 gallon carboy would act similar to open fermentation until the point the carboy head space fills with CO2. After that point, the scenario would act like a full 5 gallon carboy, because it’s full of 1 gallon of beer, and 4 gallons of CO2. The extra CO2 would then bubble out of the airlock as if it were coming from 5 gallons of beer.

:cheers:

Of note: Carbon Dioxide is considerably heavier than most of the other gases found in your standard atmosphric mix. SO? So, it is going to fill up the “headspace” from the bottom up until it expels anything lighter and then begins to expel the CO2 as well. In a fermentor kept still the beer likely just cannot get to the O2 (or any other gasses) due to the Co2 blanket sitting on top of it even before it pushes those gasess out of the lock.

Vulkin

Do it. I ferment 5 gallons in 8 gallon fermenters, only a gallon difference in head space. I occasionally do 2 gallon starter batches for lagers in 6.5 gallon buckets.

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