Carbonation differences - bottle vs keg

[RoatanBill]

I've been watching some videos and reading about carbonation. Over and under carbonation has come up several times when referring to the keg version and I came up with a thought.

A keg is a big "bottle" that holds, say, 5 gallons of beer. If one were to treat the keg as an actual bottle and drop in the corn sugar as one would do for real bottles, wouldn't that produce the equivalent to the bottled beer?

Measuring the natural pressure developed in the fermentation process would yield the replacement pressure to be used via a CO2 cylinder as beer is removed from the keg to maintain the initial pressure down to the last drop.

What's wrong with this idea?

 

[CU_tony]

You sure can naturally carb in a keg, that will however produce trub and take time at room temp unlike force carving with gas.
It's perfectly doable, however that are reasons that so many people force carb in the keg

 

[PADave]

I've read to use 3/4 the priming sugar in the keg that you would use for bottles, and then let the gas from the bottle do the rest, to prevent over carbonation. This is my plan if I ever get my keg setup, that has been sitting in my garage for months, in service.

 

[RoatanBill]

OK

So, I guess you're telling me I didn't invent a new process.
I'm devastated at that news.

Thanks for the info.

 

[Yooper]

I've read to use 3/4 the priming sugar in the keg that you would use for bottles, and then let the gas from the bottle do the rest, to prevent over carbonation. This is my plan if I ever get my keg setup, that has been sitting in my garage for months, in service.

It's actually more like 1/2 of the amount you would use if you were bottling.

If you're bottling 5 gallons and would normally use 5 ounces of priming sugar (by weight), then 2.5 ounces would be the correct amount in a 5 gallon keg.

The reason has to do with heaspace. Even though there is some headspace in the keg, there is less in the keg than in 53 bottles with 1 inch of headspace per bottle.

Keeping it at room temperature for three weeks, using 2.5 ounces of sugar, will mean carbonated beer when you put it in the kegerator and hook it up to the tap.

 

[brandonlovesbeer]

I've bottle conditioned a keg. It was awesome. But you do eventually have to add co2 as the keg drains.

 

[Yooper]

I've bottle conditioned a keg. It was awesome. But you do eventually have to add co2 as the keg drains.

Yes, and if you don't the beer will go flat with time. Using the c02 tank to "push" the beer is needed. For short term, one of those "c02 guns" will work to push the beer but won't keep it properly carbonated so for a party or something like that it'll work just fine.

 

[RoatanBill]

What about my idea of using the yeast generated pressure to define the "natural" pressure the beer wants to have and use that pressure as the CO2 pressure to simply make up for the loss of beer as it's consumed. That "natural" pressure represents the equilibrium discovered by all the players inside the keg and should be the value to keep that equilibrium in tact as beer is removed.

I'm trying to discover what that "natural" pressure is supposed to be. I realize adding more yeast food increases the pressure, but I suspect there's a curve involved and also a sweet spot in that curve where pressure and taste both come out favorably. Maintaining that exact pressure intuitively seems like a good idea to me.

 

[Yooper]

What about my idea of using the yeast generated pressure to define the "natural" pressure the beer wants to have and use that pressure as the CO2 pressure to simply make up for the loss of beer as it's consumed. That "natural" pressure represents the equilibrium discovered by all the players inside the keg and should be the value to keep that equilibrium in tact as beer is removed.

I'm trying to discover what that "natural" pressure is supposed to be. I realize adding more yeast food increases the pressure, but I suspect there's a curve involved and also a sweet spot in that curve where pressure and taste both come out favorably. Maintaining that exact pressure intuitively seems like a good idea to me.

How would you do that without adding c02?

Like your description- a keg is a big bottle. If you open a bottle of soda, and pour it, it's great for a few days and then it will go flat if you don't add more c02. The same is true for beer. A keg is a big bottle. If you remove beer, and don't replace it with the c02, you'll have a big bottle of flat beer.

The laws of physics do come into play. If you dispense, you'll have to replace. If you don't dispense, and it stays sealed it will stay as is forever.

All gasses seek equilibrium, and that's why kegging works so well.

 

[RoatanBill]

How would you do that without adding c02?

I'm not suggesting NOT adding CO2. I'm suggesting using bottled CO2 gas to mimic what I refer to as the "natural" pressure the fermentation process produced so as to keep that system in equilibrium as beer is removed from the keg.

The CO2 the yeast produced would be less likely to try to come out of solution if there was a force trying to keep it there. That force is the bottled gas at the same pressure the yeast produced.

I bring this up as a way of trying to hit equilibrium and not have over or under pressurized beer in a keg.

 

[Soulshine2]

I've been watching some videos and reading about carbonation. Over and under carbonation has come up several times when referring to the keg version and I came up with a thought.

A keg is a big "bottle" that holds, say, 5 gallons of beer. If one were to treat the keg as an actual bottle and drop in the corn sugar as one would do for real bottles, wouldn't that produce the equivalent to the bottled beer?

Measuring the natural pressure developed in the fermentation process would yield the replacement pressure to be used via a CO2 cylinder as beer is removed from the keg to maintain the initial pressure down to the last drop.

What's wrong with this idea?

I'm new to this but I am very fortunate to have received a copy of Charlie Papazians book - the Complete Joy of Home Brewing when I got most of my equipment from a good friend of mine. I'm sure everyone in here has read it at one point and time but I had a reading marathon yesterday and the points covering carbonation keg vs bottle was one of them. It has to do with the proportionate size of the vessel and the effects of the priming sugar. For a 5 gallon batch in bottles priming sugar should be no more than 3/4 cup so you don't get bottle bombs. The amount for a keg is only 1/3 cup or you stand the great chance to over foam .

 

[PADave]

I'm not suggesting NOT adding CO2. I'm suggesting using bottled CO2 gas to mimic what I refer to as the "natural" pressure the fermentation process produced so as to keep that system in equilibrium as beer is removed from the keg.

The CO2 the yeast produced would be less likely to try to come out of solution if there was a force trying to keep it there. That force is the bottled gas at the same pressure the yeast produced.

I bring this up as a way of trying to hit equilibrium and not have over or under pressurized beer in a keg.

Isn't this exactly how a serving out of a keg works? The beer gets carbonated which ever way you choose, reaches an equilibrium, beer is removed, replaced by the gas, and equilibrium is maintained. There are charts out there that already got this all figured out.