By Dave Miller (Brewing Techniques)
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Q: I have a 5-gal Cornelius keg that I use for my homebrew. However, I have never been completely satisfied that I’ve achieved the correct amount of carbonation. Usually the brew is a little flat. What methods would you suggest for carbonating beer in a keg? I’m interested in both natural and artificial carbonation techniques, and please be as specific as possible.
DM: The surest way of achieving a precise degree of carbonation is to carbonate the keg artificially, using a carbonation temperature/pressure chart such as the one shown in Table I. This method also has the advantage of avoiding a keg fermentation, which means a clearer beer in the keg and less yeastiness on the palate. Of course, if you are making Hefeweizen or if you simply prefer natural carbonation, by all means prime the keg like a big bottle, using corn sugar (glucose) or gyle (wort).
If you wish to carbonate naturally, I believe that glucose will give more repeatable results because it is 100% fermentable. As I said on the last question, brewing is an art, so ultimately you have to go by taste and trial in getting the carbonation level where you want it. Start with 1/3 cup of corn sugar and, if that proves too little, increase gradually until you get it where you want it to be.
Artificial carbonation is simply a matter of following a few rules. First, chill the beer to near the freezing point before racking it into the keg. Second, take the temperature of the beer in the keg before sealing it up. Third, apply gas pressure and release it a few times to purge air from the headspace. Fourth, find the beer temperature on the chart and look along that row until you find your desired carbonation level. Then, look along the other axis to find the correct head pressure. Set the gas regulator to that pressure, and agitate the keg until you no longer hear gas flowing through the regulator during agitation. This can take quite a bit of shaking. At the end of the process, you should have achieved the desired volume of carbonation in the keg. Store the keg in a refrigerator, and, if the fridge is not set to the same temperature as the beer, adjust the head pressure if necessary to maintain carbonation.
One final thought — if you follow these procedures and still get consistently flat beers, a couple of other possibilities merit consideration. One is that your taste does not agree with the conventional wisdom on carbonation. You may prefer fizzier beer, and there is nothing wrong with that. If you have been going for 2.5 volumes, try carbonating to 3.0; that may suit your taste better. After all, it’s your beer.
The other possibility is that you might have an equipment problem — for example, a slow leak in your gas system somewhere. This would cause loss of head pressure and carbonation over time. The best way to track down leaks is to spray a soap solution on all joints and connections and look for bubbling. Usually such leaks can be fixed merely by tightening a nut or screw, but sometimes you have to take the connection apart and replace a washer or other seal. In checking for leaks, don’t neglect the keg itself: the lid and fittings (both gas and beer) on the Cornelius keg are frequently the culprits.
Yet another possibility, if your artificially carbonated beers are consistently flat, is that your regulator gauge is wrong. We have about 28 carbon dioxide pressure gauges at our brewery, and some of them are way off. You might be able to check this by substituting another gauge, but in any case trust your taste buds, not the readings. Carbonate your beers to the level you prefer, and if the numbers say that you are out of line, remember that instruments share with humans the capability of lying.
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Guideline for degrees of carbonation at various beer temperatures. |
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Pounds per Square Inch |
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|
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
|
30 |
1.82 |
1.92 |
2.03 |
2.14 |
2.23 |
2.36 |
2.48 |
2.60 |
2.70 |
2.82 |
2.93 |
3.02 |
|
|
|
|
31 |
1.78 |
1.88 |
2.00 |
2.10 |
2.20 |
2.31 |
2.42 |
2.54 |
2.65 |
2.76 |
2.86 |
2.96 |
|
|
|
|
32 |
1.75 |
1.85 |
1.95 |
2.05 |
2.15 |
2.27 |
2.38 |
2.48 |
2.59 |
2.70 |
2.80 |
2.90 |
3.00 |
3.11 |
3.21 |
|
33 |
|
1.81 |
1.91 |
2.01 |
2.10 |
2.23 |
2.33 |
2.43 |
2.53 |
2.63 |
2.74 |
2.84 |
2.96 |
3.06 |
3.15 |
|
34 |
|
1.78 |
1.86 |
1.97 |
2.06 |
2.18 |
2.28 |
2.38 |
2.48 |
2.58 |
2.69 |
2.79 |
2.90 |
3.00 |
3.09 |
|
35 |
|
|
1.83 |
1.93 |
2.02 |
2.14 |
2.24 |
2.34 |
2.43 |
2.52 |
2.63 |
2.73 |
2.83 |
2.93 |
3.02 |
|
36 |
|
|
1.79 |
1.88 |
1.98 |
2.09 |
2.19 |
2.29 |
2.38 |
2.47 |
2.57 |
2.67 |
2.77 |
2.86 |
2.96 |
|
37 |
|
|
|
1.84 |
1.94 |
2.04 |
2.14 |
2.24 |
2.33 |
2.42 |
2.52 |
2.62 |
2.71 |
2.80 |
2.90 |
|
38 |
|
|
|
1.80 |
1.90 |
2.00 |
2.10 |
2.20 |
2.29 |
2.38 |
2.48 |
2.57 |
2.66 |
2.75 |
2.85 |
|
39 |
|
|
|
|
1.86 |
1.96 |
2.06 |
2.15 |
2.25 |
2.34 |
2.43 |
2.52 |
2.61 |
2.70 |
2.80 |
|
40 |
|
|
|
|
1.83 |
1.92 |
2.01 |
2.10 |
2.20 |
2.30 |
2.39 |
2.47 |
2.56 |
2.65 |
2.75 |
|
41 |
|
|
|
|
1.79 |
1.88 |
1.97 |
2.06 |
2.16 |
2.25 |
2.34 |
2.43 |
2.52 |
2.60 |
2.70 |
|
42 |
|
|
|
|
1.75 |
1.85 |
1.94 |
2.02 |
2.12 |
2.21 |
2.30 |
2.39 |
2.48 |
2.56 |
2.65 |
|
43 |
|
|
|
|
1.72 |
1.81 |
1.90 |
1.99 |
2.08 |
2.17 |
2.26 |
2.34 |
2.43 |
2.52 |
2.61 |
|
44 |
|
|
|
|
1.69 |
1.78 |
1.87 |
1.95 |
2.04 |
2.13 |
2.22 |
2.30 |
2.39 |
2.47 |
2.56 |
|
45 |
|
|
|
|
1.66 |
1.75 |
1.84 |
1.91 |
2.00 |
2.08 |
2.17 |
2.26 |
2.34 |
2.42 |
2.51 |
|
46 |
|
|
|
|
1.62 |
1.71 |
1.80 |
1.88 |
1.96 |
2.04 |
2.13 |
2.22 |
2.30 |
2.38 |
2.47 |
|
47 |
|
|
|
|
1.59 |
1.68 |
1.76 |
1.84 |
1.92 |
2.00 |
2.09 |
2.18 |
2.26 |
2.34 |
2.42 |
|
48 |
|
|
|
|
1.56 |
1.65 |
1.73 |
1.81 |
1.89 |
1.96 |
2.05 |
2.14 |
2.22 |
2.30 |
2.38 |
|
49 |
|
|
|
|
1.53 |
1.62 |
1.70 |
1.79 |
1.86 |
1.93 |
2.01 |
2.10 |
2.18 |
2.25 |
2.34 |
|
50 |
|
|
|
|
1.50 |
1.59 |
1.66 |
1.74 |
1.82 |
1.90 |
1.98 |
2.06 |
2.14 |
2.21 |
2.30 |
|
51 |
|
|
|
|
|
1.57 |
1.64 |
1.71 |
1.79 |
1.87 |
1.95 |
2.02 |
2.10 |
2.18 |
2.26 |
|
52 |
|
|
|
|
|
1.54 |
1.61 |
1.68 |
1.76 |
1.84 |
1.92 |
1.99 |
2.06 |
2.14 |
2.22 |
|
53 |
|
|
|
|
|
1.51 |
1.59 |
1.66 |
1.74 |
1.81 |
1.89 |
1.96 |
2.03 |
2.10 |
2.18 |
|
54 |
|
|
|
|
|
|
1.56 |
1.63 |
1.71 |
1.78 |
1.86 |
1.93 |
2.00 |
2.07 |
2.15 |
|
55 |
|
|
|
|
|
|
1.53 |
1.60 |
1.68 |
1.75 |
1.82 |
1.89 |
1.97 |
2.04 |
2.12 |
|
56 |
|
|
|
|
|
|
1.50 |
1.57 |
1.65 |
1.72 |
1.79 |
1.86 |
1.93 |
2.00 |
2.08 |
|
57 |
|
|
|
|
|
|
|
1.54 |
1.62 |
1.70 |
1.77 |
1.83 |
1.90 |
1.97 |
2.04 |
|
58 |
|
|
|
|
|
|
|
1.51 |
1.59 |
1.67 |
1.74 |
1.80 |
1.87 |
1.94 |
2.01 |
|
59 |
|
|
|
|
|
|
|
|
1.56 |
1.64 |
1.71 |
1.77 |
1.84 |
1.91 |
1.98 |
|
60 |
|
|
|
|
|
|
|
|
1.54 |
1.62 |
1.69 |
1.75 |
1.82 |
1.88 |
1.95 |
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To use this chart: First find the temperature of your beer along the outside vertical edge. Look across until you reach the carbonation level desired (the numbers in the grid express the volumes of carbon dioxide; 1 L of beer containing 3 L of carbon dioxide at standard temperature and pressure is said to contain 3 volumes of carbon dioxide). Then look up to the top of that column to find the required pressure, and set your regulator accordingly. |
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