First time filling keg with priming sugar - question on headspace

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mattsearle

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I have recently bought some corny kegs and have a batch ready to be kegged or bottled, but I don't yet have the regulator and CO2 bottle (should be here in about a week).

I need to get the beer out of the FV as I need it for my next brew this weekend, so I figured I have 2 choices, prime the keg with sugar, or bottle the batch. This doesn't really give me too many problems at the moment.

My question is regarding the head space in the keg. I have about 21 litres of finished beer (about 5.5 us gallons I believe), and would like to fill maybe 8 500ml (16oz) bottles for friends, then keg the rest, about 17 litres (4.5 us gallons).

I know the keg is supposed to take 19 litres (5 gallons), so I am going to be a little short of a full keg but do I still prime with the same sugar as I would normally? Do I have to vent the air from the keg after a while to leave a CO2 blanket, or is this not quite so easy when priming with sugar rather than CO2?

Thanks
 

Onkel_Udo

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I have recently bought some corny kegs and have a batch ready to be kegged or bottled, but I don't yet have the regulator and CO2 bottle (should be here in about a week).

I need to get the beer out of the FV as I need it for my next brew this weekend, so I figured I have 2 choices, prime the keg with sugar, or bottle the batch. This doesn't really give me too many problems at the moment.

My question is regarding the head space in the keg. I have about 21 litres of finished beer (about 5.5 us gallons I believe), and would like to fill maybe 8 500ml (16oz) bottles for friends, then keg the rest, about 17 litres (4.5 us gallons).

I know the keg is supposed to take 19 litres (5 gallons), so I am going to be a little short of a full keg but do I still prime with the same sugar as I would normally? Do I have to vent the air from the keg after a while to leave a CO2 blanket, or is this not quite so easy when priming with sugar rather than CO2?

Thanks
If you are using a priming calculator, style, volume of beer and packaging method...yes.

How are you priming the bottles? they will required a higher volume per mL or oz of liquid than the kegged volume...about double.
 
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mattsearle

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If you are using a priming calculator, style, volume of beer and packaging method...yes.

How are you priming the bottles? they will required a higher volume per mL or oz of liquid than the kegged volume...about double.

Do you mean twice as much priming sugar per ml in the bottles as the kegs? I wasn't aware of that?! Good thing I posted this up!

I was planning on batch priming the whole batch, then bottling some and kegging the rest?
 

william_shakes_beer

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There's a third option: keg the beer, seal it up and put it on co2 when it arrives. That's what I would do. Right now I have 4 kegs waiting their turn on co2 in the kegerator.
 
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mattsearle

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There's a third option: keg the beer, seal it up and put it on co2 when it arrives. That's what I would do. Right now I have 4 kegs waiting their turn on co2 in the kegerator.

This did cross my mind, but i was only concerned that this would expose the beer to oxygen for that period, especially with the larger headspace?
 

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How are you priming the bottles? they will required a higher volume per mL or oz of liquid than the kegged volume...about double.

I keep seeing people say that, but it makes no sense. A keg is just a big bottle if you are naturally carbonating. I measured one of my 5 gal ball lock cornies, and the headspace (after filling with 5 gal liquid) is about 5/16 gal (5 cups.) So, the headspace is about 5.9% of the liquid volume. I also measured a standard 12 oz bottle. For the bottle, the headspace is 5.6% of the liquid volume. So, you actually need to create proportionately more CO2/volume for the keg to get the appropriate amount of CO2 to get the required headspace pressure. It's probably an insignificant difference, but 1/2 the sugar in a keg vs. a bottle just isn't going to cut it. With less than 5 gal in the keg, you should actually be using more sugar/beer volume to prime, in order to generate the required CO2 to properly pressurize the headspace.

Brew on :mug:
 
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mattsearle

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I keep seeing people say that, but it makes no sense. A keg is just a big bottle if you are naturally carbonating. I measured one of my 5 gal ball lock cornies, and the headspace (after filling with 5 gal liquid) is about 5/16 gal (5 cups.) So, the headspace is about 5.9% of the liquid volume. I also measured a standard 12 oz bottle. For the bottle, the headspace is 5.6% of the liquid volume. So, you actually need to create proportionately more CO2/volume for the keg to get the appropriate amount of CO2 to get the required headspace pressure. It's probably an insignificant difference, but 1/2 the sugar in a keg vs. a bottle just isn't going to cut it. With less than 5 gal in the keg, you should actually be using more sugar/beer volume to prime, in order to generate the required CO2 to properly pressurize the headspace.

Brew on :mug:

This is exactly what I thought, surely the headspace is bigger than in a bottle obviously, but there's more beer so relative to the beer the ratio of headspace is like a big bottle! I think I'll batch prime the lot, bottle some and keg the rest, then when my CO2 arrives I can top up the carbonation if need be? I cant imagine that it will possibly be overcarbonated with a larger headspacd? At least then there should be some protection until the co2 arrives.
 

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Another thing to keep in mind is that most corny kegs will not properly seal without a burst of CO2. I typically naturally carb my kegs and after racking and adding priming sugar I hit each keg with 20-30 psi. This seats the lid and also allows me to purge O2 from the headspace. If you naturally carb in the keg without hitting it with some CO2 I would bet any CO2 created from naturally carbing will be lost.
 

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Another thing to keep in mind is that most corny kegs will not properly seal without a burst of CO2.

I think "most" might be a bit overstated. Of my five, 3 will always seal if you a have freshly lubed lid o-ring and one is crapshot. The fifth is obviously a mismatched lid so even with the oversized, soft o-ring it will not seal without at least an initial 15 psi. The others will seal just from the CO2 released from the agitation of transfer.

Now, I will say that the o-ring condition and bit of experience on how to drop the bail while keeping it centered makes all the difference.
 

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Maybe it's just me but I don't really trust mine to seal well without adding a little burst from the tank either.
 

Onkel_Udo

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Maybe it's just me but I don't really trust mine to seal well without adding a little burst from the tank either.

IT certainly is easier that way.

Until you try it, you don't know if your kegs will seal or not. Slap a single second or two of of 4-6 psi on it. Leave it alone for a week. Hit the relief valve to see if goes "pfst".

I did mention it takes a bit of futzing to center a lid and lock down it down without it shifting off-center.
 
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mattsearle

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I think "most" might be a bit overstated. Of my five, 3 will always seal if you a have freshly lubed lid o-ring and one is crapshot. The fifth is obviously a mismatched lid so even with the oversized, soft o-ring it will not seal without at least an initial 15 psi. The others will seal just from the CO2 released from the agitation of transfer.

Now, I will say that the o-ring condition and bit of experience on how to drop the bail while keeping it centered makes all the difference.

This is my first time kegging, so how do I go about lubing the o-ring (ooh sir!)?
 

Onkel_Udo

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This is my first time kegging, so how do I go about lubing the o-ring (ooh sir!)?

First, I would lube all the o-rings which requires keg disassembly. Then you apply a thin layer of Keg Lube or ANY food grade o-ring lube...to the best of my knowledge they are all petroleum jelly (so really just Vaseline but from a food-safe manufacturer). I use the stuff for soft-serve ice cream machines because it is cheap.

You just want a very thing coal on all surfaces of the o-ring. The only one I lube every time is the lid but I am also a rebel that does not disassemble my keg each time to clean and sanitize it.
 

BrookdaleBrew

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I keep seeing people say that, but it makes no sense. A keg is just a big bottle if you are naturally carbonating. I measured one of my 5 gal ball lock cornies, and the headspace (after filling with 5 gal liquid) is about 5/16 gal (5 cups.) So, the headspace is about 5.9% of the liquid volume. I also measured a standard 12 oz bottle. For the bottle, the headspace is 5.6% of the liquid volume. So, you actually need to create proportionately more CO2/volume for the keg to get the appropriate amount of CO2 to get the required headspace pressure. It's probably an insignificant difference, but 1/2 the sugar in a keg vs. a bottle just isn't going to cut it. With less than 5 gal in the keg, you should actually be using more sugar/beer volume to prime, in order to generate the required CO2 to properly pressurize the headspace.

Brew on :mug:

You'd think that but my anecdotal evidence tells me that if you use the same amount of sugar as you would bottling, you will end up with very over carbonated beer. I've had good results using about half what a bottle priming calculator says. I can't explain the science behind it, I can only tell you what I've seen happen multiple times.
 

Revvy

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What am I missing here? If your gas is arriving in a week, why don't you just leave it in the fermenter until the co2 comes and keg it then? Give it another week of conditioning, and don't monkey around with anything else?

If you want to brew again, go buy another bucket.... You can never have too many Fermentation Vessels. And buckets are fricken cheap.
 

doug293cz

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You'd think that but my anecdotal evidence tells me that if you use the same amount of sugar as you would bottling, you will end up with very over carbonated beer. I've had good results using about half what a bottle priming calculator says. I can't explain the science behind it, I can only tell you what I've seen happen multiple times.

If you get over carbonation using the same amount of sugar per batch as bottling, then your fermentation was not finished when you kegged. There is no other explanation. The amount of CO2 created per gram/oz/kilogram/pound/ton of sugar is fixed. To be over carbonated, you need to have more sugar than you think you have. If you can't explain your results, then you don't really know what's going on. Fermentation, and resultant CO2 production, are well established science. I'm still waiting for a plausible explanation for all of the anecdotes about keg carbing.

Brew on :mug:
 

william_shakes_beer

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You'd think that but my anecdotal evidence tells me that if you use the same amount of sugar as you would bottling, you will end up with very over carbonated beer. I've had good results using about half what a bottle priming calculator says. I can't explain the science behind it, I can only tell you what I've seen happen multiple times.

I have never done natural carb in a keg, but if you think about it: when bottling, you rack twice. Once to the bottling bucket, once to the bottle. Each time you leave sediment and yeast behind. When keg conditioning you rack once. I suspect there's more yeast cells in the keg than the sum of yeast in all the bottles.
 

doug293cz

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I have never done natural carb in a keg, but if you think about it: when bottling, you rack twice. Once to the bottling bucket, once to the bottle. Each time you leave sediment and yeast behind. When keg conditioning you rack once. I suspect there's more yeast cells in the keg than the sum of yeast in all the bottles.

Final carbonation level only depends on the level of residual CO2 in the beer when you package, and how much fermentable sugar is in the beer. The amount of yeast does not affect the total amount of CO2 generated, but can affect the rate at which CO2 is generated.

Brew on :mug:
 

Unicorn_Platypus

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How much headspace is needed to prime with sugar in a keg?

I have cut gas diptubes and can closed transfer to the brim.

My typical prodedure for kegging is to close transfer to the brim & I then pull a pint out of the headspace.

Will that be enough headspace to prime in a keg or would I need more?
 

doug293cz

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How much headspace is needed to prime with sugar in a keg?

I have cut gas diptubes and can closed transfer to the brim.

My typical prodedure for kegging is to close transfer to the brim & I then pull a pint out of the headspace.

Will that be enough headspace to prime in a keg or would I need more?
You don't need any headspace for priming. The only purpose for headspace is to prevent high hydraulic pressure due to expansion/contraction of the beer with changing temperature. This hydraulic pressure can pop caps or break bottles. In a keg, the worst it should do is blow a little beer out the PRV.

Brew on :mug:
 

Unicorn_Platypus

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You don't need any headspace for priming. The only purpose for headspace is to prevent high hydraulic pressure due to expansion/contraction of the beer with changing temperature. This hydraulic pressure can pop caps or break bottles. In a keg, the worst it should do is blow a little beer out the PRV.

Brew on :mug:
Good answer! I'm thinking I'll connect a spunding valve at ~60 psi as a secondary pressure relief valve for safety in case the primary one on the keg lid gets clogged.

I'm planning on dry hopping and priming simultaneously so don't wanna risk the prv getting clogged with junk at a high pressure
 

doug293cz

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Good answer! I'm thinking I'll connect a spunding valve at ~60 psi as a secondary pressure relief valve for safety in case the primary one on the keg lid gets clogged.

I'm planning on dry hopping and priming simultaneously so don't wanna risk the prv getting clogged with junk at a high pressure
A spunding valve is at least as likely to clog as a PRV, but having two PRVs will improve the odds.

Brew on :mug:
 

Unicorn_Platypus

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A spunding valve is at least as likely to clog as a PRV, but having two PRVs will improve the odds.

Brew on :mug:
I have a double filter inlet from the. Flotit manufacturer jammed into the bottom of one of their silicon gas diptubes.

I do this on the gas post of my fermzilla too in order to prevent material blown off from clogging the gas posts

I think this is less prone to clog with dry hops than a regular prv 😉🍻

Floating Dip Tube DFI (Double Filter Inlet) for Keg Buoy, Fermzilla, All Rounder | eBay

 
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