Wednesday, April 27, 2011

Force Carbonation

When you first start kegging your beer the one thing you need to decide is what method you are going to use to force carbonate your beer. Below I have set out the steps for force carbonating your beer using two different techniques. The first few steps are the same regardless of the method you are going to follow, then the techniques diverge, I will lay out the steps to follow for each technique and then I will give the reasons I follow one of the techniques.

My set up, a 6kg Co2 tank sits outside
the fridge and a gas line is fitted through
a hole drilled in the kegerator door.
Step 1 - Transfer your beer to the keg, connect the Co2, turn on,  and purge the keg with a few lifts of the pressure release valve. Doing this will help seal the lid properly and also expel any oxygen present in the deadspace at the top of your keg.
Step 2 - Turn off the gas and let your keg refrigerate for 24-48 hours. This will allow the temperature of the beer to drop which will result in easier absorption of the Co2 once you start to force carbonate.

Method 1: Rock and Roll
Step 3 - Turn the gas on and raise to a PSI of about 45, you will now hear the Co2 entering the keg, now gently place the keg across your knee making sure the 'gas in' post is at the top of the keg*. Now gently rock the keg back and forth across your knee for about one minute. As you do this you will hear the Co2 entering the keg constantly. It is now being absorbed into the liquid and the tank is refilling the dead space with more Co2.
Step 4 - After a minute turn off the gas at the regulator and continue to rock the keg back and forth. The gauge on your regulator should now start to drop. You are looking for it to stop at between 20-23 PSI, if it falls below this it is under gassed and you may need to repeat steps 3 and 4. If it finishes above this the beer may be over gassed and so you will need to vent the excess gas.
Step 5 - Leave the keg to sit for one hour and then turn the gas back on to 15 PSI. Your beer should now be carbonated to the right level.

*this is done to try and alleviate the risk of liquid entering the gas line, if liquid gets sucked up the gas line to your regulator it will ruin it.

Method 2: Set and Leave
Step 3 - Turn the regulator to the desired PSI based on the table below. In order to determine the liquid temperature of your beer, place a spirit thermometer in a glass of water in your kegerator while the beer is left to cool for 24-48 hours, this should give you an accurate enough reading for the liquid temperature inside your kegerator.

Temp 9 10 11 12 13 14 15 16 17
7 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8
8 1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7
9 1.85 1.9 2 2.1 2.2 2.3 2.4 2.5 2.6
10 1.8 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5

Temperature is listed down the left hand side and PSI across the top, so for example if the liquid temperature is 8c and you are looking for a carbonation level of 2.1**, then you need to set your regulator to 11.

Step 4 - Be patient, following this method your beer should be carbonated to the desired level in 4 days, however if you can leave it for a week then all the better.

** The level of carbonation you aim for really depends on the style of beer you are brewing and also your personal preferences, here is a rough guide of what you should be aiming for with the most typical styles:

My current APA carbonating
at a PSI of 10.
British Style Ales: 1.5 - 2
Stouts/Porters: 1.7-2.3
American Ales/Lagers: 2.2 - 2.7
German Wheat Beers: 3.3 - 4.5

My Technique
Personally I use the set and leave method. I find this to be very consistent, and extremely straight forward. You determine the PSI based on the table above, set your regulator and then leave it alone. Moreover when you come to serving your beer you can leave the regulator as is and leave your gas turned on all the time (although do make sure you have no leaks). Due to the fact that equilibrium will have been achieved between the keg and Co2 tank the only gas that will be used is as you dispense the beer and so it is an easy, no hassle way of carbonating and dispensing your beer.


TaleOfAle said...

Nice step by step guide Mark.

I usually naturally carb my beers in the keg and just use the gas for downward pressure when serving but I have had to force carbonate once or twice and use the rock and roll method.

Mark (Halite) said...

Hey Reuben, have to say I have never tried natural carbonation in the keg. Do you use standard bottle priming calculators to work out the sugar addition, or is there a difference when priming in a keg?

TaleOfAle said...

Same works. Consider the keg a bottling bucket.

Mark (Halite) said...

Cool, I might give it a try.