Blow off question

[K_Squared]

Hi,

In the beginners section of the Complete Joy of Homebrewing, Papazian says to use a 5 gallon carboy with a blow off tube. He then says "if you are using a 6 1/2 gallon glass carboy...it is not necessary to affix a blow-off hose." However, he lists the advantage of doing a blow off, which makes me want to do it.

So, here is my question: I was planning on using a 6.5 gallon carboy for my first stage fermentation. Will there be too much headspace (I'm going to make a 5 gallon batch) to get the advantages of using a blow off tube? Or, do I need to use a 5 gallon carboy to get blow off.

Thanks for any thoughts on this,
Ken

 

[twistr25]

I have not had a crazy fermentation yet, but I always use a blowoff for the first couple days just in case. Much better to be safe than have krausen covered walls.

 

[MarkIafrate]

A lot depends on the type of beer you're doing. I did a really simple pale ale recipe with a low expected ABV in my 6.5 gallon glass carboy and just used an airlock. However, if I was doing one of the big stouts I make I'd do the blowoff tube. So if your beer is expected to be big, use the tube for the 6.5, if not, the airlock will be fine.

If you're doing 5 gallons in a 5 gallon carboy, definitely use the tube, though.

 

[zeg]

Buzz off.

(Blow off answer.)




I would put a blow off tube on anything for the first few days, or until the Krausen has fallen, unless there was at least 25% headspace. All but one of my beers has blown off, even with nearly a gallon of headspace on a 5 gallon batch. The one that didn't was a lager pitched at around 45 degrees and fermented at 48 for the first few days, and even that Krausened enough to put some scum on the bottom of the cap.

I don't think there is any good reason not to start with a blowoff tube. Do it for a few days, then unplug the tube and swap in an airlock. It takes 30 seconds plus a few minutes to rinse out the hose and catch jug. All it takes is avoiding one overflow and it's worth the small amount of time invested.

 

[duboman]

Do not ferment a 5 gallon batch in a 5 gallon carboy! 6.5 gallon bucket or carboy is ideal for a 5 gallon batch as primary. I always use a blow off rig regardless as I have no desire to deal with clogged air locks and walls plastered in krausen! After the first week I swap it out for an airlock.

 

[zeg]

If you want to end up with 5 gal, duboman is correct. I can pull off 5 gallons in my secondary using a 6 gallon primary, even leaving behind half a gallon of trub, but much smaller than that and you'll end up with less come bottling time.

That's not a terrible thing, though. You can easily adjust to make a 4.5 gallon batch, or just make it a 5 gallon batch and leave a little head space or fill it up and let it blow off down to its maximum capacity. If you already have the 5 gallon fermentors around and don't want to acquire more, either of these approaches will work. Just be careful if you have a whole lot of hops because there's some risk of a clogged blow-off.

You could also keep making a 5 gallon batch, then find a gallon glass jug (either buy one, or more thriftily, buy a gallon of cider and save the jug). Split the wort and yeast between the two and throw a stopper/airlock on the jug. If you end up doing a secondary, you can always combine the two. (This is a very common thing to do for wine/mead, when additional rackings are necessary and head space is undesirable.)

 

[K_Squared]

One of the things I was concerned about was NOT getting the benefits of blow off if I used a 6.5 gallon carboy. That is to say, I was worried that with the head space in a 6.5 gallon carboy (for a 5 gallon batch) at fermentation stage 1, I wouldn't get the blow off that reduces undesirables (e.g., excess yeast, excessively bitter hop resin, etc, that Papazian says is reduced with blow off). I was trying to figure out if I should use the 5 gallon so that I would get enough blow off. It sounds like I'll likely get blow off even in a 6.5 carboy, which is what I was hoping for....right?
Thanks.

 

[twistr25]

I haven't had a blow off yet and have had no issues. I use one because I'm lazy and don't want to clean up a really sticky mess.

 

[zeg]

I think the benefits of blow-off (in terms of eliminating off flavors) are overstated. I wouldn't worry about it, certainly not until you have everything else in your process working at a level where you can do an A-B test with and without blowing out the Krausen and trust that any difference is due to that. Until you're that consistent, I don't think this is worth even thinking about. Install the blow off just in case, but don't worry about ensuring you get one.

 

[ludomonster]

You're over-thinking it. Most of people's concerns with blow-offs surround the mess it can make. People don't usually use it as a part of the process to improve the beer.

 

[duboman]

You're over-thinking it. Most of people's concerns with blow-offs surround the mess it can make. People don't usually use it as a part of the process to improve the beer.

Correct and in reality if you are using a true top cropping yeast strain and do not allow for proper krausen development and it all gets blown out you are actually losing quite a bit of viable yeast.

Really the only purpose of the blow off is to handle that excessive, crazy fermentation that could potentially clog the airlock to the point that the pressure becomes so extreme that the lid blow off and sends krausen all over the place.

BTW, if it happens we all really appreciate pictures!:fro:

 

[dadshomebrewing]

I am going to guess that you will learn the benefit of a blowoff tube the same way many of the rest of us did.

By cleaning kreusen off the walls, and floor, and whatever was near the carboy when it blew.

It's a mistake each of us makes exactly once.

Fwiw

 

[mojobently]

Sunday I brewed a Tripple, dropped it in a 6 gallon carboy, I checked it when I got home and it was chugging away as it should be. I walked by it about 2 hours later and just happened to look over and found kreusen spewing out of my air-lock. I had never had a blow off and Im sure I narrowly avoided one last night.

 

[K_Squared]

Thanks, folks, for your thoughts on this.
I've learned:
(a) always use a blow off tube (e.g., for the first several days or week).
(b) the advantages of blowing off part of a batch (via the tube in part a) are, at best, minimal.
(c) forcing blow off (via the tube in part a) need not be a strategy for reducing undesirables and thereby increasing the quality of the beer.
This was really helpful to improve my thinking on some of these things.
Thanks,
Ken

 

[dadshomebrewing]

you missed one.

d) having a blow off tube will increase the value of your brewing experience because you won't have to wash walls.

 

[BxBrewer]

All of what said above. Should be a sticky. Ive been playing around with FermCapS with the boil,starter and fermintation. It really helps.

 

[zeg]

(b) the advantages of blowing off part of a batch (via the tube in part a) are, at best, minimal.

Also, I was reading through Palmer last night for other reasons and came across a comment that the brown gunk at the top of the Krausen is intensely bitter, so should not be mixed down in. This is where he points out that you can blow it off or skim it off the top, but he also says he has always found it adequate to let it stick to the sides/top of the fermentor and simply be careful not to disturb it when racking.