Hello folks, new homebrewer here still working on setting up equipment and the like for the first batch. In reading Complete Joy of Homebrewing, I noticed a brief mention that a 5 gallon batch in a 6.5 gallon carboy does not need a blowoff assembly during primary fermentation, but you can skip directly to putting the airlock on and let the headspace absorb the pressure/krauzen. Has anyone used this method? Does it work or am I heading for a missile launch? Thanks for any input!
I usually use 8 gallon buckets, which obviate the blowoff thing. When using carboys, I'll just use tin foil for the first few days of active fermentation, which gives time to see whether a blowoff tube is needed. Otherwise, I put on an airlock after the initial growth phase is finished. 5 gallon batches definitely blow out of 6.5 gallon carboys.
It depends. Your variables are OG, yeast strain, temp, oxygen level, and probably some more I can't think of. Your source is giving generic advice. Specifically, you should always be equipped to put on a blow-off tube. If not so equipped, it's a mad scramble to get it set up . . . meanwhile you are creating a very sticky mess. The worst case is a simple airlock may get clogged and the pressure "blows" the lid. Or the krasuen may never reach the top of the lid. You feeling lucky? Consider being able to attach a 1/2" tube to the center of your airlock stem or place a 5/16" tube directly in the lid opening. You can use cheap vinyl tubing from HD. Search youtube for "homebrew blowoff" and you'll see some wild videos. PPPPP
I use a 6.5 gallon carboy for 5 gallon batches, and have never had an issue, as there is plenty of head space for a massive krausen to form. I use fermcap though (unless I forget, see my "epic equipment fail" thread...) and wouldn't risk it without.
I use a 6.5 gallon carboy for 5-gallon batches, and I've had krausening foam get into my blow-off tube a couple of times, so it can happen. I think in both cases the OG was somewhere around 1.070-1.080.
