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Batch size VS fermenter?

Jeremiah87

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Not only am I a new user but I am completely new to brewing. I haven't even brewed my first batch yet but I already have a question.
Is it safe to ferment smaller batches in larger containers or does the liquid/air ratio negatively affect the beer? For example, one gallon of brew fermenting in a 5 gallon bucket. I want to start with small batches for a few reasons...

-The space between my stove and overhead oven is probably not big enough for a 4+ gallon brew kettle
-Starting out, I only have 18 bottles, I will continue to collect
-If I create a bad batch I have less to waste/drink
-I can have more varieties in my practical storage space
-I'd like to experiment with all grain which is easier to manage in small batches

I'm aware I could use a smaller fermenter but I suspect it won't be too long before I want to do bigger batches so I might as well buy what I need once instead of twice. Thanks in advance!
 
Sounds like you are giving this some good thought.  I brew 10 liter batches as my std recipe size and move up to a 20 liter batch for those recipes that I want to keep and age.  I use 3 gal. carboys for both.  A 5 gal. batch splits nicely between two carboys and allows me to experiment with different yeasts or dry hopping/added flavorings.  Meanwhile, the carboys fit the bulk of my brewing.
 
Normally, you'll want a fermenter that is slightly larger than your batch size. Example: a 3 gallon bucket for a 2 gallon batch, a 6 or 6.5 gallon bucket for a 5 gallon batch, etc. The closer your batch size is to your fermenter size the less air will stay on top of your beer. However, you'll want a bit of extra room in the primary for all that foam and other blow-off materials as active fermentation can become quite lively.  This being said, eventually the positive pressure in your fermenter will push all the air out and leave the headspace filled with CO2 from the fermentation process.

I use 8 gallon buckets or 7.5 gallon carboys for my 5.5 gallon batches.

However, once you go to a secondary or are aging something like sour over a long time period, then you'll want to eliminate headspace as much as possible.  At these stages, there is no longer krausen to worry about, but there also is very little CO2 being produced.  You need the CO2 to push out any air, so that you don't have the oxygen in the headspace.  When you only have the top two or three inches of the neck of a carboy for airspace, it takes a very small volume of C)2 to fill that space.

I make some sour beers that require 1-2 years of aging, and I make sure that my volumes are correct, so that I don't have oxygen in contact with the beer.  Some of the microbes that I use to sour my beer, when in contact with oxygen over a long period of time will result in the production of vinegar.  Who needs 5 gallons of malt vinegar?
 
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