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It makes the beer go. It makes the beer go fizz. Gas
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GasMost of you reading this already have some sort of CO2 supply, likely a 5 lb tank, that you use to push your beer through the system. You have likely figured out by now that the higher the pressure on the keg, the faster you pour your beer. On one hand it’s that simple, on the other hand, it’s a lot more complicated than that. The Short StoryKeep your CO2 system at 12-14 pounds per square inch gauge pressure (psig). This will keep just the right amount of CO2 in your 38º F beer. Not flat, not fizzy. The Medium StoryThis is best explained using a few examples:
The Long StorySo either you are interested in why you should keep your beer system at 14 psig, you are skeptical of our advice, or you need another five to ten minutes worth of material to read. No matter what the reason, I’m glad you’re still reading. I’ll try to keep this accurate, complete and simple. Bear with me. The predominant flavor in beer is actually the result of carbon dioxide dissolving in the beer. When CO2 dissolves in water, it forms carbonic acid, H2CO3. Acids tend to have a unique, almost sour taste, which in moderation, tastes good. Most brewers, and certainly all commercial brewers, know this, and hence are very interested in exactly how much CO2 is dissolved in their beer. Most domestic American beers have between 2.6 to 2.8 volumes* of CO2 dissolved in them. Typical micro-brews and craft beers have 1.8 to 2.4 volumes, while some Irish stouts have as little as 1.2 volumes. Assuming you want to taste your beer as the brewer intended it to taste, you need to keep just that amount of CO2 dissolved in your beer. No more, no less. So the question is: How? This is where it gets tricky. You can still bail out and go back to The Short Story (see above). If you reviewed your Henry’s Law and LeChatlier’s Principle, you are ready to forge on. Or if you ever attended a class without doing the reading ahead of time, you have what it takes to make it through. When a gas (in our case, CO2) dissolves in a liquid (in our case, beer) it is due to a slight attraction between the gas molecule and the liquid molecule. Rather than just simply forming a bubble and escaping, the gas molecules remain bonded to liquid molecules. It is not a very strong bond, though, so as the beer molecules bounce around against each other, the gas molecule may leave one liquid molecule and bond with another. If the ratio of gas molecules to beer molecules gets to high, the gas molecules start to join up, form bubbles, and escape. This causes foam. It turns out that at room temperature the amount of CO2 that can happily stay dissolved in beer is 0.8 to 0.9 volumes. If the beer is cold, however (say….38º F), there is less bouncing around among the beer molecules, and a CO2 molecule is a little more likely to stay attached to a particular beer molecule and so there is less chance that the CO2 molecules will join up and form a bubble. At 38º F, it turns out that there is room for 1.5 volumes of CO2 to stay in solution. But wait! The brewers spent all this time and effort getting 2.6 volumes of CO2 into their beer and now I’m telling you that there is only room for 1.5 volumes. How do we keep all of that CO2 in there? Simple. We force it. We make the space in the keg above the beer so crowded with CO2 that for every CO2 molecule that makes an escape another one gets pushed back in. Chemists call this “dynamic equilibrium.” At 38º F with 2.6 volumes of CO2 in solution, 14 psig of keg pressure is just enough to do the trick. So what if you want to pour your beer faster? Just turn up the pressure, right? Not so fast, Speedy. When you crank up the pressure on the keg, you make the space above the beer so crowded with CO2 that even at 2.6 volumes a CO2 molecule would still rather dive into the beer than hang out in the over-crowded head space. With enough pressure, you could ensure that the elusive dynamic equilibrium isn’t reached until the beer is at 2.9, 3.0 or even higher concentrations of CO2. Not only will this affect the taste of your beer, but look at it from a CO2 molecule’s perspective. In the keg, the head space above the beer was just as crowded as the beer itself. There is no great motivation to leave. Now all of a sudden, the beer is in a glass on the bar and there is essentially no CO2 pressure left. It will be a all-out, jungle-rules, mad dash for freedom. The beer-CO2 system is scrambling for equilibrium. Chemists call this “LeChatlier’s Principle.” You and I call it “wild, uncontrolled foaming.” TurboTap
Our goal here at TurboTap is to allow cold, properly carbonated
beer to be poured quickly and efficiently. We have spent many years
developing a simple way to do this. In the next update I will write
about a few simple hardware changes that will allow you to get the
most out of your TurboTap system.
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