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By request, here is a posting that I made on Brewboard a long time ago that explains my carbonation process. Keep in mind that there is no reason to use priming sugar if you are kegging and have CO2 handy. The priming sugar or "natural carbonation" will not make your beer carbonate differently, have different bubbles, or taste different. It will however add a very small amount of alcohol to the beer, but again nothing noticeable.

Dissolved CO2 is dissolved CO2 for our purposes, and the controlling factors are temperature, pressure, and time. You can only affect one of these, and that is time. Agitating the liquid exposes more of the liquid to the gas, thus making the CO2 mix into solution more rapidly. Shaking the beer doesn't do anything more than help speed the process along. Don't believe anyone that tells you they don't shake because it affects the beer. The important factors are temperature and pressure. Use the standard chart to find the volumes of CO2 you want, and get going! Also, all carbonation using CO2 under pressure is force carbonation, regardless of the speed you perform it at.

Use the carbonation chart at the link above, or use the same chart available in many places around the web. At the bottom of this page are more links for carbonation that might help. Don't make this tougher than it is, and don't try to re-invent the wheel, just follow the process and learn the rules to be happy!

The best way of carbonating your beer is to set the pressure and leave the beer alone in the fridge for a few weeks. That solves two issues. The first is nice even carbonation, and the more important one is proper conditioning. So many people don't let the beer condition properly and are in a hurry to carbonate and drink it. Both carbonation and conditioning can happen at the same time in the fridge ot kegerator, so patience is the best method, and it is nearly foolproof. (OK, it is only fool-resistant, they make better fools every day).

I just don't see why people have a problem with carbonating by the numbers, regardless of shaking (rapid force carb) or not (regular force carb).

As for the main question "how much CO2 is in my beer?" The answer is still simple by using the chart. For a given pressure at temperature, you have given volumes of CO2, with small variations not really measurable by human taste or feel. If you are carbonating your beer by a proper method where you know the temp and pressure, you already know how much CO2 is in solution. If you make a "bleed-off gauge" or whatever you might call it (NB part #K088), you can measure the pressure, but that is not really ever needed because the proper pressure is what your regulator should be set at for serving. If you are just setting your regulator to some arbitrary number and letting the beer sit until it "seems right" you deserve whatever happens.

After doing this for a long time now, I have a decent grip on rapidly force carbonating my brew. Before I do any racking, I chill the vessel/fermenter for a few days whether it be primary or secondary, to make sure the yeast drops out as much as possible, then I'm racking cold clear beer into the keg to start with and don't need to chill the beer much if any before carbonation. If you can't chill your fermenter, no worries, just get the beer in the keg cold before carbonating.

I call the process "chasing the needle" as I will detail how to reduce the pressure as the CO2 goes into solution without any backflow issues that many people wrongly assume must happen.

Once I get the beer into the keg, I start with setting the regulator to about 50psi for the first shaking segment, connect the CO2 line to the GAS (IN) port, and then lay the keg on its side and roll back and forth for about 15 seconds listening to the bubbles. I then turn down the gas pressure slowly while rocking the keg and listening to the bubbles, and it is critical that you are slowly lowering the pressure while the gas is still flowing.

I don't go below the point where beer can flow back into the line. I continue rocking the keg and the bubbles will start again as the gas pressure goes into solution and the overall pressure drops so the gas flows again. Once the bubbles become fast again I continue rocking while turning the gas down again, probably 5psi at a time while you hear the bubbles. When you drop the pressure the bubbles may slow, but this is the time you should be rocking the keg, and as the carbonation goes into solution, the bubbles will pick back up again.  I do this again and again until I get to about 20psi on the regulator. At this point I'm really close to the final pressure so I want to drop the pressure to a few pounds above my target and shake until the bubbles slow again and I stop. This only takes a few minutes. This usually gets you to a place where the beer is carbonated enough to be served, but still usually needs some time at the proper final pressure to be perfect. Stopping a bit early prevents me from over-carbonating, and virtually nobody could ever tell that you are not at an exact level of carbonation. If you get really good at this you can just about get it 100% perfect this way very quickly and be perfect, but people tend to over-carb so I suggest caution.

It is still better than setting at a higher pressure and leaving it for hours or days and not knowing where your carbonation level is. This method is a controlled way to get close to your target carbonation, and you can then get the last few PSI done by leaving it overnight and be perfect.

This method is nothing new, and yields very accurate and trouble-free rapid carbonation. I've never over-carbed doing this because the high-pressure segments are quite short, and you have an audible reference to let you know when the pressure is reaching equilibrium. I'll be glad to show anyone how to perform this method if you are in the Tampa Bay area. Everyone has their own method and this is just what I've found to be the most efficient after doing this for a while now. You will find that there are variables such as the headspace inside the keg and such, but they are not critical if you follow the process.

We also assume at this point that you have a balanced serving system. If you do not have a balanced serving system, and are doing strange things to serve your beer, that is a whole different story.You should be able to set your regulator at the same pressure as you carbonated your beer for, and serve perfectly. If not, fix it. Skip the tricks and do it right, and thank us later.

If you ever meet someone who tells you to just set the regulator at some higher pressure and walk away for a few days until it seems right, kick him in the head for the rest of us because that causes more problems and more redundant internet postings than anything else I've ever seen. Seriously... if your buddy swears that you can leave it overnight at 30psi, the next guy will tell you two days at the same pressure. All of them are lucky if it works, and they are mostly full of shit and will have no consistent carbonation.

As I don't claim to invent this stuff, but try to communicate the way I've found successful, here are some links to other source material to help you on your gas filled adventure!

Yeah, that's me, caught while rolling a keg to carbonate it quickly. You'll notice that the CO2 input is at the lower side, so I can hear the gas bubbling into the keg. As long as you are keeping a greater pressure going into the keg, you won't have a problem with backflow. Once the pressure starts to equalize you need to be careful.