How much space is too much in the fermenter?

[Coastalbrew]

Hi everyone,
I mostly do 5-5.5 gal batches right now but would like to do 7 or 8 gal from time to time. For my 5 gal batches I use a 6.5 gal plastic fermentation bucket. I have a 10.5 gal SS kettle that I'm not using and am thinking of turning it into a fermenter. My question is, will the 10.5 gal pot have too much head space for my 5 gal batches?

Thanks!

 

[McKnuckle]

At the beginning it will be fine; near the end, probably not, especially if you keep your beer in primary for conditioning after active ferm is done.

 

[Coastalbrew]

@McKnuckle why is that? At the end of fermentation there should be a good pillow of CO2 sitting on the beer, so no oxygen. Right?

 

[WBCo]

Do you have a way to seal the kettle? Something air tight? The "blanket of CO2" thing is a little misleading. Doesn't quite work like that. If the vessel is not airtight oxygen will get it and mix with the CO2 produced from fermentation.

 

[McKnuckle]

Right, as @WBCo says, you won't have a CO2 blanket for long if the top is not sealed tightly. Most kettle lids are not (at all).

One might safely assume that O2 is not going to suddenly come whooshing in to oxidize the beer, and that's probably true, but it seems to seep in gradually enough to be a potential problem.

One of my fermentation solutions is a 4 gallon stainless pail with a glass lid that sits loosely, but solidly, on the top, thanks to a neoprene seal around the circumference. I use binder clips to secure the lid during fermentation. But I don't need an airlock, because the setup is not airtight.

As soon as active primary ferm is over (3-7 days), I rack quickly to a keg where I will condition and ultimately serve. You could call it a secondary, but it never leaves the keg, so... not really.

I would not do an extended rest of 2-3 weeks in the pail as many homebrewers seem to practice in their primary fermenters. Same would apply to your kettle I would think.

 

[Qhrumphf]

Do you have a way to seal the kettle? Something air tight? The "blanket of CO2" thing is a little misleading. Doesn't quite work like that. If the vessel is not airtight oxygen will get it and mix with the CO2 produced from fermentation.

This.

Even if absolutely 100% still (which in the real world is nigh impossible), gasses will diffuse into the blanket. As soon as any draft (as produced by moving a bucket lid), and it happens even faster.

Larger headspace means more oxygen potentially reaches your beer. If you're VERY careful that can be prevented (pro breweries half fill fermenters all the time so there's no inherent problem otherwise). Step one is putting in a positive CO2 flow each and every time the lid is open. Otherwise keeping it sealed works too.

And of course any fermenter leaks will do more damage faster, too.

Edit: didn't read carefully, you're asking about using a kettle? If you can get a gasket to seal the lid to the body and clamp it down to form an airtight seal with a drilled hole for a stopper/airlock, that could work quite well. But a loose lid, yeah that'll be a problem. Even with open fermentation beers are moved to sealed tanks when active fermentation (and CO2 production as a result) dwindle down.

 

[Coastalbrew]

My plan is to fashion a silicone seal similar to what @Brewzologist does in the thread here: https://www.homebrewtalk.com/forum/threads/diy-stainless-steel-fermenters.490055/ and then to drill a hole in the lid for gasket and an air lock. The kettle does not have clips to hold down the lid, but I have a couple of solutions in mind for that as well.

Assuming an air tight construction, are there any other pit falls to having so much head space?

 

[Qhrumphf]

Do you keg and have a CO2 supply? If so, every time you open for a gravity reading (and the entire time during) put in a low flow of CO2 (5-10 PSI should do) towards the surface of the beer to try and keep pushing air out. That'll at least lessen the potential damage.

As I said, pros half-fill fermenters regularly so there's no *inherent* problem as long as air is kept out.

The other issue is if you cap or spund- it changes the amount of CO2 produced or carb picked up by head pressure compared to if it was fuller. But if you're not fermenting in a conical/unitank/keg that you're putting under pressure then that doesn't apply.

 

[RM-MN]

My plan is to fashion a silicone seal similar to what @Brewzologist does in the thread here: https://www.homebrewtalk.com/forum/threads/diy-stainless-steel-fermenters.490055/ and then to drill a hole in the lid for gasket and an air lock. The kettle does not have clips to hold down the lid, but I have a couple of solutions in mind for that as well.

Assuming an air tight construction, are there any other pit falls to having so much head space?

Is a brick one of the solutions you have in mind? It won't take much to seal it if you have a silicone gasket to seal against.

I regularly ferment 2 1/2 gallon batches in a 6 1/2 gallon pail. Sometimes the lid seals and the airlock bubbles, sometimes it doesn't. I don't notice any difference in the beer produced. Even lifting the lid (just the edge, just enough to drop the hops in) to dry hop doesn't show much effect except that the hop aroma dissipates perhaps a bit quicker than it should. I've never seen cardboard taste of oxidized beer with my setup.

 

[Anyhowe]

In answer to your question the headspace does not really matter as it will always mix.

However, see all the responses above about sealing as the mixing notion is correct. Don’t forget, if it wasn’t mentioned, that sealing will likely generate pressure as total fermentation is rare.

Personally, I would not worry about it at all. Although I now ferment in sealed pressurized kegs, I never worried about it before and don’t ever recall an oxidization issue. But I know how much fun it is to ‘improve’ our process so good on you. YMMV

 

[SEndorf]

Just my 2 cents.... but I would opt for a plastic fermenter of an appropriate size before I ruined a nice SS kettle by drilling a hole in the lid.

 

[Coastalbrew]

Thanks for the feedback.
Cheers!

 

[tstevado]

I'm curious if anyone has any experience with the ferment-in-a-kettle kit for the Anvil kettles? I was thinking of picking up a 10gal kettle for brew in a bag and then just fermenting in that - part of the reason is for doing kettle sours where I would leave it for a bit on lacto first, then boil and ferment normally. Keeping it in the same vessel just seems more convenient than moving it back and forth.

But my initial question was same as the OP. With the FIAK kit would that provide enough seal to avoid the oxygenation issues with the approx 5gal of headspace in the kettle?

 

[Cyclman]

Fermentation produces huge volumes of co2, as long as the fermenter is sealed.
https://www.ikegger.com/blogs/ikeggerworld/how-much-co2-is-produced-during-fermentation

 

[Elric]

I'm curious if anyone has any experience with the ferment-in-a-kettle kit for the Anvil kettles? I was thinking of picking up a 10gal kettle for brew in a bag and then just fermenting in that - part of the reason is for doing kettle sours where I would leave it for a bit on lacto first, then boil and ferment normally. Keeping it in the same vessel just seems more convenient than moving it back and forth.

But my initial question was same as the OP. With the FIAK kit would that provide enough seal to avoid the oxygenation issues with the approx 5gal of headspace in the kettle?

I admittedly only used it a few times before putting it to the side, but the fiak kit worked great for me with my 5.5 gallon anvil. I even did some macgyvering with it so I could very lightly pressurize it to allow for closed transfers when done. The primary reason I stopped using it was that using it meant I was without the use of my kettle for the duration of my fermentation period! I know have multiple fermenters so I can have several beers on the go at one time.

 

[Melicious]

Just my 2 cents.... but I would opt for a plastic fermenter of an appropriate size before I ruined a nice SS kettle by drilling a hole in the lid.

I'd rather "ruin" a safe SS kettle than use a plastic fermenter that leaches phthalate disruptors into the brew, reducing testosterone & sperm count/motility.

https://www.gq.com/story/shanna-swan-interview