Keg Force Carbing Methods Illustrated

+1 For stickey post. New to carbing and find this to be the most informed.

bump

holjim said:

BierMuncher -- Do you mean that you'll rack to your keg (without sugar or gas) and let it sit for two weeks or do you shoot a bit of gas into it and then let it sit at room temp prior to chilling and force carbing?

Thanks!

Jim

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Just enough gas to purge the air out and get a good seal on the lid. I'll usually seat the lid with about 20PSI.

findthefish said:

Yeah it seems like there's been a lot of these types of questions lately. Now hopefully people actually see this before posting.

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I did.......

Me too! Proud owner of a 3 day old kegging system.

Saw the sticky and just kegged my first two batches: apfelwein and an Anchor Steam clone.

Many thanks. This definately helped me to understand the process.

Ok So I attempted to follow Bobby M's instructions, but I'm still having some issues.

So I kegged last Saturday. The fridge is set to 38F. I let the kegs sit in the fridge for 4-5 hours before I connected any lines. I want 2.6 vol of carb.

I set the regulator to 37 PSI then shook the kegs for few mins then let them sit for 24 hours. Then I turned off the gas, released the excess pressure, turned the gas back on and set the regulator to 12.3 for the rest of the week.

Last night I turned the gas off, released the excess pressure, turned the gas back on and set the regulator to 5PSI for serve. From both kegs I poured 2 glasses and got 95% foam 5% beer, the beer was just slightly carbonated. So I turned the regulator back up to 12.3 and hear I am.

What am I doing wrong? Or am I just impatient?

Thanks,

Ouch.. you're overcarbed. The burst carb thing in post #1 is described as leaving the keg on gas at 3x the chart pressure for 24 hours and not shaking the crap out of the keg first. The shaking process at that elevated pressure probably got you to the 2.5 volumes area and the additional 24 hours was icing on the cake. You're probably at 4 volumes now. You'll need to vent the keg a few times over a day's period. This can be accelerated by taking the keg out of the fridge.

Let's first talk about what kind of tubing you have between the keg and faucet. Length and inside diameter are important.

Thanks for the quick reply..

I purchased this Learn To Brew: Two Tap Door Mount Hombrew Kegerator kit and using the default lenghts 6' for beverage out. I'm not sure on the ID, not at home at the moment. I can check when i get home.

Yeah I also did something similar with shaking the keg at 30 psi for a few minutes, but without waiting any time for the keg to rest on high pressure. However, now several hours later having let the keg sit quietly in the fridge off gas, I am getting 95% foam 5% liquid, and the beer itself tastes FLAT.

I have 6' of 3/16" line and am dispensing at 12 psi. There is considerable foam in the beer line -- would that convert the beer coming out of the keg into foam if I can't clear it out, or is something else going on?

How in the heck could it be overcarbed, yet taste entirely flat??

beergorila said:

Yeah I also did something similar with shaking the keg at 30 psi for a few minutes, but without waiting any time for the keg to rest on high pressure. However, now several hours later having let the keg sit quietly in the fridge off gas, I am getting 95% foam 5% liquid, and the beer itself tastes FLAT.

I have 6' of 3/16" line and am dispensing at 12 psi. There is considerable foam in the beer line -- would that convert the beer coming out of the keg into foam if I can't clear it out, or is something else going on?

How in the heck could it be overcarbed, yet taste entirely flat??

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All that foam is all the carbonation. It's like if you take any carbed beer and shake it in the glass, it will foam up and the beer will be flatter due to loosing the gas into the foam.

Did you vent your keg before trying to serve it off the gas? If you try and serve it at 30 psi with only 6 ft of tubing it will come out of the tap too fast causing it to be too turbulent causing only foam. Try venting it then hooking it up to the gas at 12 psi.

For whatever it's worth, I am reverting to the shake method. The only reason is that I think it's more time efficient. Screw ups can be fixed in less time than any other method. This is just my own preference. Great post BobbyM.

I don't know if this has been covered here or somewhere else, but with the chart, how long does it take to reach the co2 volume at the particular temperature based on the psi?

It's somewhere between 2-3 weeks to reach full equilibrium.

I too overcarbed my beer. I need to purge the tank of CO2 and reduce the PSI. Is there an estimate of how many times I need to purge the tank of gas? My guess is it depends on how much I am over carbed but wanted to check.

So the theory is that if I set the regulator for 10 PSIG for 2 weeks at 40 degrees F it will be at approx 2.3volumes? Will it stay at that if I leave it at 10 PSIG or will it continue to absorb more gas? (assuming I leave it at a constant Temp).

Your theory is correct. The temp/pressure chart is a long term fixed equilibrium. Once it hits the 2.3 volumes, it will stay there. I'm sure there are formulas that say how many times you'd have to vent the headpressure to reduce volumes, but it would certainly be based on temp, beer volume, headspace volume and current volumes of co2 dissolved. Way too much to worry about. Just trial and error should work.

Note, if you need to downgrade your carbonation level, it's best to leave the gas diconnected as your going through the venting process. It's silly to apply gas to a headspace that you're just going to vent all over again.

Yeah I didn't think that one through when I typed that huh? LOL!

Bobby_M said:

Your theory is correct. The temp/pressure chart is a long term fixed equilibrium. Once it hits the 2.3 volumes, it will stay there. I'm sure there are formulas that say how many times you'd have to vent the headpressure to reduce volumes, but it would certainly be based on temp, beer volume, headspace volume and current volumes of co2 dissolved. Way too much to worry about. Just trial and error should work.

Note, if you need to downgrade your carbonation level, it's best to leave the gas diconnected as your going through the venting process. It's silly to apply gas to a headspace that you're just going to vent all over again.

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Bobby,

I posted another thread yesturday but reaally did not get the answer I was looking for, it seems like you really have a handle on this kegging thing, I racked from the primary to my keg with 1/3 cup of priming sugar, purged it with about 5 or 10 lbs and let it sit at room temp for 3.5 weeks, i put it in the fridge on Monday and tapped it last night and its flat, tastes great but flat, i turned up the lbs to 12 and just tryed it again and still flat.

When I tapped it it still had pressure because I hooked up the beer line first, but I guess the seals could have leaked.

What is the best choice at this point, 30 lbs for a day? Shake the keg at 30?
Please give me some ideas if you can.

Bobby_M said:

I'm not sure if there's some magic math that can be done to figure out exactly how much of an initial pressure shot it would take at room temp to have a beer fully carbed without any additional constant gas. I've tried playing with the numbers but it made my head hurt so I gave up. If I understand it properly, you have to compare the headspace volume to the entire keg volume to know how the pressure will drop.

10psi? Heck no. That's 10psi in a headspace 1/10th the size of the whole keg. Once it absorbs into the beer, you get like 1 psi equilibrium which is .75 volumes. Let's try 40psi. 1/10th is 4 psi so room temp would be .9 volumes.... Hey, if it's a bitter, you might be close now.

If you're shooting for 2 volumes, it would take 20 psi equilibrium at room temp, which is about 200 psi in a 1/10th headspace.

Athough it doesn't get me all the way there, I still hit my kegs with 40psi before I tuck them into the basement for a short warm aging period (If I have enough supply flowing already of course). I'd rather start with .9 volumes when it hits the kegerator than 0 volumes.

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If you're in a hurry to drink it, try 30psi overnight if the beer is cold. After 24 hours, disconnect the gas, reset the regulator to 12psi, pull the purge valve on the keg for a second or two and reconnect the gas disconnect. The 30psi for 24 hours might not get you 100% there, but it will continue to carb at the 12psi setting also. You just don't want to overcarb because it's a pain to offgas it. I suspect you did have a leak at some point.

Bobby,

Thanks for the reply, I am will do that and see how it goes.

So what is the best way to do this? I did have new seals on the keg, should have I purged it with 30 psi at the beginning and that might have sealed it better? I really wanted it to just do the natual carb thing, just like a big bottle,

Honestly, I've never sugar primed a keg so I'm not the guy to ask. However, I know that keg lube on the main Oring is one way of ensuring a better seal. I've read that a lot of people hit it with 20psi to seat the lid before tucking it away to carb.

Bobby,

Thanks for the help, I will drop you a line to let you know how I make out

Thanks again,

Jeff

Bobby,

Well I turned it to 30 psi for 23 hours and it turned out perfect, how simple a fix, I thank you so much for the insight, now my next decsion is to figure out how I will do it in the future, i am thinking that I will just age it and then do the same thing, 30 psi on a chilled keg for 24 hours and see if it is ok.


Thanks again,

Jeff

Bobby_M said:

Your theory is correct. The temp/pressure chart is a long term fixed equilibrium. Once it hits the 2.3 volumes, it will stay there. I'm sure there are formulas that say how many times you'd have to vent the headpressure to reduce volumes, but it would certainly be based on temp, beer volume, headspace volume and current volumes of co2 dissolved. Way too much to worry about. Just trial and error should work.

Note, if you need to downgrade your carbonation level, it's best to leave the gas diconnected as your going through the venting process. It's silly to apply gas to a headspace that you're just going to vent all over again.

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Ok, this is the question I asked myself yesterday. Of course I couldn't come up with an answer, because I didn't know it, that's why I asked myself in the first place!

So, let's say that I carb my beer with 20 lbs of pressure for a short time, then drop the keg pressure to serving pressure, say 6 lbs (cause I haven't looked it up yet). You're saying that the beer will stay carbed just like it was when I dropped the pressure on the keg? It wont start losing carbonation over time? Or if so, how much time are we talking?

Also, where can I find a digital copy of that carb chart? I want to keep a copy in Excel format, and maybe print a nice one off to put on the kegerator... Plus a chart with different beer styles and their proper carb levels.

So heres my situation. I cranked my reg to 30psi, gas in, rolled in my lap for a few minutes, bled it off, back in the fridge, pulled a "sample", pulled a little more "sample", then 20psi overnight, and I just came to work leaving it at about 12 (sampled a bit more this morning). I figured this would be a reasonable combo of the burst and set and forget methods. I think it will be good. The sample this morning had alot of foam (since it was at 20psi on a 5' hose), but I could tell the beer wasn't done carbing yet so I think I'm in good shape. Any suggestions?
Thanks

The hardest thing is recognizing when a beer is really carbonated vs. when a beer has simply been blown through a serving line under intense pressure. They both have a foamy head but only one is a result of CO2 coming out of solution that was originally dissolved in the beer.

I can make a few more true statements that might also help. There are a few things that increase the speed at which CO2 will dissolve in the beer (the carbonation process).


1. Higher pressure applied to the headspace. We know that based on the charts, a higher pressure will ultimately end up at a carbonation level well higher. Even if you target is 2 volumes, setting the pressure so that it would ultimately reach 4 volumes will get you to 2 volumes quicker. BUT!!!! you'll never really know when to stop and purge. It's a guess.

2. More CO2 to beer surface area. In a typical corny, the contact between beer and co2 is about 28 square inches (the area of the surface of the beer). That's a pretty small area give 5 gallons of beer. The tricks to increasing surface area is physical agitation and gas diffusion. When you agitate the keg, it makes the headspace of co2 turn into a million bubbles immersed in the beer presents a much larger surface area than 28sqin. You can also achieve a similar effect by putting a stainless stone on the incoming gas and having it immersed in the beer. Using either of these surface area techniques with the pressure from the chart is the ONLY way to be 100% sure that you are not overcarbing in the process.

Of course, you can do a combination of these to get there faster but the odds of overdoing are increased.

Just like in my first post, the only time I'd agree with speeding carbonation is if the beer has already been properly aged already. If not, the tried and true set and forget method accomplishes a predictable carb level and aging in one process.

I also don't want people to think that just because they increase pressure and agitate the keg that carbonation is absolutely instantaneous. Just for discussion's sake, let's say you have a 35F keg of beer and you raise the pressure to 30psi. Given the chart, with about 2-3 weeks wait, the beer will achieve 4.5 volumes of co2. Maybe you really want 2 volumes but you're trying to get it done faster. Is it 2 days? 3 days? I'm not sure, but it's definitely not 2 weeks. Now, same example with temp/pressure but let's say you shake the crap out of the keg at the same time for 5 minutes. How many volumes are you at immediately after? Who knows, it could be 2 volumes.

If you're into being exactly to style and want reasonable accuracy on carb levels, stick with chart and wait. If you really want to hurry but still be reasonably accurate, use the speed methods and then get a bleeder valve with a pressure gauge on it. How's what work?

If you have a keg sitting around that is in some state of fixed carbonation but you don't know what that is, you can put a pressure gauge on it to find out. The caveat is that it has to be a fixed carb level where the CO2 dissolved in the beer is at equilibrium with the pressure in the headspace. If that is met, you can read the head pressure, measure the beer temp and find the volumes on the chart.

I'm going to start kegging soon. I saved your info to my "favorites" for future reference.

Thanks,

dude my mind is thoroughly blown...what? muhuhawhaw ( Spicoli laugh)
Ill have to read this when im not drinking 9.5 tripple homebrew

Great info.

What about the technique of putting the gas onto the Beer Out line so the co2 can bubble up through the beer? Any do this? I read it on another site.