Carbonation question

[Horseflesh Inferno]

Next week I'm going to keg a stout that needs to age for another month or so. It'll be about 4.5 gallons in a 5 gallon keg. I want to just pressurize it and detach it from the co2 and let it age in the house. Does anyone know what my initial pressure would need to be so that it equals out to 12 psi once all the gas is absorbed and the pressure equalizes? That way once it's done I can just chill it and go. It's a sanke keg so I can't use a carb stone on this one.

 

[doug293cz]

Can't do that. I have a spreadsheet that calculates the pressure needed for what you are proposing, and the pressure comes out about 140 psi for your beer volume. I'm traveling so won't likely be able to write a more complete answer before Thursday.

Brew on

 

[mashdar]

There are some major unknowns re the starting point of the beer, but the result is pretty much what Doug said no matter what.

You can think of one "volume" as adding ~ 15psi in gas-land. So if we're generous and assume 1 gal head space and 4.5 gal beer, adding 1 volume to the beer will need 4.5*15=68psi, plus the residual 12psi = 80psi.

And that's assuming you're storing it at serving temperature. At 60F it's probably +20psi (I don't have my spreadsheet handy)

But you probably don't have 1 gal head space, and you likely want more than 1 vol added, so the math blows up pretty quick.

Maybe you should aggressively fast carb and then spund down to ~ 20psi at 60F? (We need the storage temp, serving temp, and vols CO2 target to give precise value.)

 

[SFC Rudy]

Next week I'm going to keg a stout that needs to age for another month or so. It'll be about 4.5 gallons in a 5 gallon keg. I want to just pressurize it and detach it from the co2 and let it age in the house. Does anyone know what my initial pressure would need to be so that it equals out to 12 psi once all the gas is absorbed and the pressure equalizes? That way once it's done I can just chill it and go. It's a sanke keg so I can't use a carb stone on this one.

Prime it like it is a beer bottle. Seal the keg with 20-30 psi and let it do its thing.

 

[mac_1103]

Does anyone know what my initial pressure would need to be so that it equals out to 12 psi once all the gas is absorbed and the pressure equalizes?

I have a spreadsheet that calculates the pressure needed for what you are proposing, and the pressure comes out about 140 psi for your beer volume.

I can't remember where I put my glasses, but Doug remembers his spreadsheets very well. You would in fact need to put 145 PSI on that keg (at 65F/18C) to end up at 12 PSI (at 40F/4C). But that would be about 2.5 volumes of CO2 and you said it's a stout. 90 PSI would give you about 1.9 volumes. So I guess the question is, how fizzy do you want your beer and how lucky do you feel?

 

[Horseflesh Inferno]

Thank you guys for the responses. I think the keg is rated at 60psi so anything above that I wouldn't want to risk. Plus it's a stout so I don't want it too fizzy. I'll probably do about 40 and let it rest, then a few weeks later do another 40 (just so my inline gas filters don't blow ). That should hopefully get it pretty decent at least, then once I tap it let the serving pressure finish the job if it needs any more.

 

[Jim R]

I would just pressurize it to 12 psi every few days when you walk past it. It just takes a few seconds and then disconnect the hose again.

In fact, this is what I always do now. I lost a tank of CO2 once when I must have had a small leak somewhere. Now as my beer is aging in the keg, I just clamp on the hose from the CO2 tank, represuurize it to about 12 psi, disconnect the hose and shut off the main valve on the tank. It takes 10 seconds every couple days. When I finally tap the keg, it is usually carbonated perfect. I even continue this as I am drinking it. I just repressurize it after I drink a couple glasses.

 

[Horseflesh Inferno]

I would just pressurize it to 12 psi every few days when you walk past it. It just takes a few seconds and then disconnect the hose again.

In fact, this is what I always do now. I lost a tank of CO2 once when I must have had a small leak somewhere. Now as my beer is aging in the keg, I just clamp on the hose from the CO2 tank, represuurize it to about 12 psi, disconnect the hose and shut off the main valve on the tank. It takes 10 seconds every couple days. When I finally tap the keg, it is usually carbonated perfect. I even continue this as I am drinking it. I just repressurize it after I drink a couple glasses.

Yeah that's probably the best idea. Since it's getting cold now I'll probably just age it in the garage right next to the kegerator anyway.

 

[bwible]

How did you end up with 4.5 gallons? You could a) brew another half gallon with extract or whatever to top up or b) add a 6 pack of a similar commercial beer or 6 beers you brewed of a similar style to get to 5 gallons

 

[mac_1103]

How did you end up with 4.5 gallons?

Why is that a problem?

 

[bwible]

Why is that a problem?

Problem is a strong word. More of an inconvenience. Its an odd batch size and I was just curious. I mean, the guy posted about it, right?

 

[mac_1103]

I mean, the guy posted about it, right?

He posted about single shot batch carbonation. He mentioned the volume of beer in the keg because it might be relevant. And it is relevant in that the extra headspace actually helps in the scenario he asked about. In fact, this would probably work if he had a gallon less in the same size keg and put 60 PSI on it. With a full five gallons you would need almost 400 PSI.

 

[Horseflesh Inferno]

How did you end up with 4.5 gallons? You could a) brew another half gallon with extract or whatever to top up or b) add a 6 pack of a similar commercial beer or 6 beers you brewed of a similar style to get to 5 gallons

I boiled off too much. I wasn't paying attention to my volume and when I put it in the fermentor is when I realized it. To me it's no big deal though, I just had a higher starting gravity than I was shooting for. From now on I'll keep a gallon of distilled water to top it off if I need to.

 

[mashdar]

I boiled off too much. I wasn't paying attention to my volume and when I put it in the fermentor is when I realized it. To me it's no big deal though, I just had a higher starting gravity than I was shooting for. From now on I'll keep a gallon of distilled water to top it off if I need to.

FWIW in theory if you were going to top off, you'd want to de-oxygenate that water. On a homebrew scale, that might meal boiling, but cooling fast or sealing without imploding a vessel is an issue. IMO don't bother.

 

[Horseflesh Inferno]

FWIW in theory if you were going to top off, you'd want to de-oxygenate that water. On a homebrew scale, that might meal boiling, but cooling fast or sealing without imploding a vessel is an issue. IMO don't bother.

Oh I meant for future brews. Topping off the fermentor before pitching the yeast. I would still boil it to sanitize it though, but yeah it's not really too big a deal so I don't know if I'll ever even bother.