# How Much Air Space In The Fermenter?



## Swizzle (4/7/08)

Ahoy

I'm into a few kit brews with additives and have been having a bit of trouble getting enough head (love life's fine thanks before you ask...). 

I've recently been advised that it's best to have no space between the wort and the fermenter to ensure no oxidisation, even if this means chucking a few bottles full of water or ??? to reduce the air space. The average 23litre brew obviously leaves a 7l gap in your average 30l fermenter so by my rough calculations I'm going to have to lob in about 8 long necks to allow sufficient displacement.

Not that I'm n0t willing to give it a go (anything for better head!) but I'd be interested to know if anyone else subscribes to this methodology.

Thanks 
Swizzle-the-new-guy


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## sponge (4/7/08)

I've put down a few 18L brews in my 30L fermenter and havent had a problem with oxidation. Fingers crosses i just didnt give myself the commentators curse ^_^ . I have a wheat beer in there atm which is only 17L because ive heard a few stories about the wb-06 going a little krausen-crazy!

The layer of CO2 is usually enough to protect the wort from that (from what i understand), which is the reason why some people open ferment??? Im more then happy to be told otherwise on this, just going by memory....


Sponge


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## peas_and_corn (4/7/08)

Firstly, oxidation shouldn't be a cause of low head- you will be able to tell if it has occurred if you detect a wet cardboard taste in your beer. Don't worry about headspace, it's no issue- oxidation is only a risk if you splash the wort after fermentation (which is why some people are wary about racking). Generally low head is influenced by what ingredients you use, so posting some of your recipes would be a good way to helping fix this problem.

Also one minor note: how do you wash your glasses? It is argued that soap residue can destroy head, and some people on this forum prefer just rinsing them out with *hot* water.


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## horner34 (4/7/08)

no need swizzle,

when the yeast get going they need oxygen and then when they crank up they produce co2 that pushes out the oxy.


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## NME69 (4/7/08)

I,ve always thought about this Question
It makes sense to me that someone should manufacture a lid which is a cone shape (the top pointing upwards) so the Co2 that is produced could push all oxygen out of the top and through the air lock? therefore eliminating any air contamination inside the fermenter. 

Or, am I wrong and I should Shut up?


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## Sprungmonkey (4/7/08)

After fermentation the CO2 will increase replacing the 02 from bottom up (as CO2 is heavier) until all o2 is expelled.


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## Swizzle (4/7/08)

peas_and_corn said:


> Firstly, oxidation shouldn't be a cause of low head- you will be able to tell if it has occurred if you detect a wet cardboard taste in your beer. Don't worry about headspace, it's no issue- oxidation is only a risk if you splash the wort after fermentation (which is why some people are wary about racking). Generally low head is influenced by what ingredients you use, so posting some of your recipes would be a good way to helping fix this problem.
> 
> Also one minor note: how do you wash your glasses? It is argued that soap residue can destroy head, and some people on this forum prefer just rinsing them out with *hot* water.




No cardboard flavours so far, in fact beer's been pretty good, with various different recipes and ingredients. I've been pretty fastidious about cleanliness and using closed fermentation so didn't really see the problem with the air space myself, although had similar advice for wine making..

Now you come to mention it I have been racking the last few batches. The culprit perhaps? Taste's been fine as mentioned, just lacking head. Any tricks to racking to minimise the risks?

So the general consensus seems to be that no-one loads their fermenter up with full beers?!

Glass washing - another one of those issues. One school of thought is that some detergent based cleaning is required to remove fats but I've always just gone the hot water. On that advice I've very tentatively washed bottles in a mild detergent solution yesterday - then rinsed and sterilised before bottling up a batch of Cascade Golden Harvest lager last night so will watch with interest to see if a) I have soapy beer or B) if the head is any better as a result of squeaky clean botles.

Many thanks.
Swiz


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## peas_and_corn (4/7/08)

If you have no cardboard, there's no oxidation. The lack of head is probably caused by something else- could you post the recipe of your last batch, that could be a cause (with my batches I tend to include grains that are known to increase head retention for example- though for you it would be different)


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## Swizzle (4/7/08)

peas_and_corn said:


> If you have no cardboard, there's no oxidation. The lack of head is probably caused by something else- could you post the recipe of your last batch, that could be a cause (with my batches I tend to include grains that are known to increase head retention for example- though for you it would be different)




Stand by on that one peas. Need to dig out the info when I get home.
Cheers.


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## Cortez The Killer (4/7/08)

Some kits don't give you very good head - coopers kits are known for it

I found when I was making kits that as I started adding carapils (a type of grain) to my batches I started getting a decent head on my beers 

Try adding 100g of carapils to each batch

Have a search for how to steep grains

Dirty glasses can also cause issues

The theory about making sure your fermenter is full is complete rubbish - you'll only be diluting your beer

Cheers


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## peas_and_corn (4/7/08)

Also, you need room for your krausen


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## barry2 (4/7/08)

Over 60 23 litre brews in my 30 litre fermenter and no oxidation.
Agree grain is good for the head.


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## sama (4/7/08)

do u meen head on the beer once its poured? If so how are u carbing/priming your beer when you bottle it?


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## pablo_h (4/7/08)

NME69 said:


> I,ve always thought about this Question
> It makes sense to me that someone should manufacture a lid which is a cone shape (the top pointing upwards) so the Co2 that is produced could push all oxygen out of the top and through the air lock? therefore eliminating any air contamination inside the fermenter.
> 
> Or, am I wrong and I should Shut up?


What, you mean like a carboy? 

OP:

Oxidation just doesn't happen in a normal fermenter, I almost knocked myself out breathing the fumes once there's that much CO2 in there once the yeast gets started. Also I tried to put 23L in a 25L fermenter once (bucket type, snap on lid), the krausen blew the lid off!


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## phonos (4/7/08)

If it has only been a problem since you started racking, it may be that your beers are taking longer to carbonate as there is less yeast in the bottle. Give them a few weeks longer in a warm part of the house then if they are still flat, then it is not a lack of priming sugar.


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## pint of lager (4/7/08)

A standard style 23 litre ferment generates about 120 litres of CO2 gas. This will effectively purge your headspace of oxygen.

CO2 gas does not form a protective layer. Gas molecules whizz around, they don't settle.


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## pablo_h (4/7/08)

If you trying to find a refrigerant leak on an evap, put your leak detector at the lowest point, the gas settles and that's where you'll detect it without ripping the evap covers off if there's a leak. If you were under attack in WW1 with mustard gas, the worse place to be was in the trenches, the gas settled. You didn't have to worry about it wizzing around, it was a usefull weapon in WW1 because it settled into all the trenches the soldiers were in.
Denser gasses settle, whether it's refrigerants, mustard gas in warfare or CO2 etc, if it's denser than air which is mainly nitrogen and oxygen, it will settle. Why do you think confined work spaces and tunnels need ventilation? Because heaver gases don't wizz around by themselves.

Take the lid off a fermenter, do you go dizzy from the CO2 just being nearby? Now stick you head in there and sniff in all the settled CO2. Feel good? I bet not, because of all the cencentrated CO2 just sitting there.
Man, oh wow, it's like it is just settling in there not wizzing out as soon as you removed the fermenter lid. 
I'm not saying the molecules stay still, but they definitely don't flow upwards through the air and crawl out of a vessel on their own.


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## peas_and_corn (4/7/08)

But hasn't that got more to do with the vessel being *relatively* sealed, making the sort of gaseous dissipation more difficult? That the CO2 left behind is because it was created under the O2 and pushed it out?


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## pint of lager (4/7/08)

Mustard gas was actually distributed as an aerosol, Wiki Mustard gas link which behaves differently to a gas.

Your refridgerant is a very large molecule, and may have a larger concentration in some spots, but it will diffuse into the air.

Carbon dioxide doesn't form a protective layer over the top of your beer. The air in the headspace of the fermenter is purged of oxygen and any other gas as your fermenting wort produces carbon dioxide. The headpspace is about 7 litres, there is about 120 litres of carbon dioxide produced during fermentation. Please don't go sniffing in the fermenter, carbon dioxide at 5% concentration is deadly.


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## Bribie G (4/7/08)

I brew to just over 24 litres so I can fill 12 two litre PET bottles. Brew starts off at about 22 litres to allow heaps of headspace then about 4 days in, when the initial frothing has settled down I quickly add 2 litres of boiled (eg de-oxygenated) water. Fermentation continues steadily and flushes out the oxygen I have introduced quite quickly. I use a bottling 'extractor' pipe with the valve at the bottom to avoid splashing and haven't had any oxy problems. 

Someone on another thread raised the idea of squeezing the PET bottle slightly before screwing on the top, thus bringing the beer right up to the top of the bottle, the conditioning rapidly creating a CO2 only space which lets the bottle return to its proper shape.
Sounds like a good idea that I'll try when I bottle a brew on Sunday.


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## pablo_h (5/7/08)

pint of lager said:


> Mustard gas was actually distributed as an aerosol, Wiki Mustard gas link which behaves differently to a gas.
> 
> Your refridgerant is a very large molecule, and may have a larger concentration in some spots, but it will diffuse into the air.
> 
> Carbon dioxide doesn't form a protective layer over the top of your beer. The air in the headspace of the fermenter is purged of oxygen and any other gas as your fermenting wort produces carbon dioxide. The headpspace is about 7 litres, there is about 120 litres of carbon dioxide produced during fermentation. Please don't go sniffing in the fermenter, carbon dioxide at 5% concentration is deadly.



Aerosol was the delivery method, it has nothing to do with the gas itself. If you read the wiki link you read that it "persisted" in the area for days, ie it didn't wiz around, it stayed where it was delivered for a while. Everything diffuses after a while, refrigerant, mustard gas, co2 etc, but thats because of winds, air pressures, temperature variations carry it, not because of the gases' natural tendancy.

I don't understand the people that say "there is no co2 layer over fermenting beer", but at the same time acknowledge that the yeast continously produces co2 during fementation, so there is nothing above the wort except co2. What is the difference between saying there is a layer, and saying that the fermenter is full of co2 and leaving at that as you do?


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