I brew 5 gallon extract/steeping grain batches in a 6 gal plastic bucket and transfer the batch to a glass carboy for a month of settling. I have 3 carboys. 5, 6, and 7 gallon. I haven't used the 7 gallon carboy yet because I have read that there is too much headspace and the beer will get oxidized. The 5 gallon is just right andI haven't had any bad batches with the 6 gallon. Am I being too cautious by not using the 7 gallon carboy?
For 5 gallon batches, the 7 gallon carboy (sure it's not 6.5?) would be fine for primary. But for secondary, you want as little headspace as possible. The exception would be if you are adding fermentables in secondary, in which case you do need some headspace.
As a precaution when using the larger carboys, especially for secondary fermentation, you can always add some CO2 to the carboy - since it is heavier than air, it will push the air out and replace it with the CO2, or at least provide a blanket of CO2 over the wort.
The problem with this is that you can't really pressurize a carboy effectively, so very little O2 will be pushed out. As far as the "blanket" goes, the gasses will mix freely over time, and lots of O2 will still reach the beer. See Fick's Laws, or Entropy if you prefer.
The 7 gallon carboy is fine for primary fermentation. I would rack it into a 5 gallon carboy with no headspace to age it further if needed.
My 5 gallon is finishing a stout. I havent't done a primary fermentation in a carboy yet. For the upcoming German Dampfbier i plan to make, would I just leave the ale longer in the 7 gallon primary carboy and skip a secondary?
I have had good luck with 10 days in the bucket then placed into 5 gallon carboy for a month before bottling. So, 4 to 5 weeks total in the 7 gallon is OK?
Four to five weeks in the 7-gallon primary will be perfectly fine. Many homebrewers these days skip a secondary, unless there is need for extended aging. I've not used a secondary in years, and I often keep a beer in my primary fermenter (a Speidel 8 gallon vessel) for 3 to 4 weeks. Cheers!
I'm still a secondary guy even tho it ain't popular. Less free headspace is always good in a secondary, but I have a lot of visited and 5 gallons of. Beer usually does not last a month so for me and my brewing schedule, oxidation is not a issue. If your beer is going to last 6 months or more, worry about headspace. Otherwise, minimize splashing when you are transferring to secondary and bottleing, and enjoy
