This article is part of a series, if you have not read the previous article please check it out first: Draft Beer 101.
Draft beer is beer that comes in bulk, usually in a keg. Unlike a bottle, where you can open the package, drink the beer inside, and recycle the container, draft is about being able to pour many glasses from the same keg over a period time, without changing the beer inside. If you buy a bottle or can of beer, open it, and drink half of it, then walk away, you’re probably not surprised to come back to find out your beer is flat and probably doesn’t taste the way it did. The goal of draft beer is to have the last pour from the keg be the same as the first, and for both to taste how the brewer intended.
Draft systems are basically three pieces. You have a source of pressurized gas, along with a regulator that allows you to control how much pressure you apply to the beer. You have the keg itself, and you have the “beer line”, tubes that carry the beer from the keg to the faucet where it’s poured.
When you open that bottle from the first paragraph and pour out half, you’re doing two things to the beer. First, you’re depressurizing the container that it was in. Second, you’re exposing it to oxygen. In draft, we’re not going to do either of those things. We’re going to set the pressure regulator to provide as much pressure to the keg as is already in there from the beer itself– remember that’s how beer stays carbonated– and by using the faucet we’re never going to allow air to flow back into the keg. If we do it right, the result is beer that tastes great with the right amount of carbonation.
This is where we start getting into the reason for these articles and the most important thing about keg conditioned draft beer. We know that different beers contain different amounts of Co2 in solution. We also know that in order to keep our beer from depressurizing we need to provide as much pressure as already exists from the beer itself. The trick is that if we don’t find the right pressure to apply to the beer, we can change it completely!!! If the beer has more pressure than the pressure applied, it’ll pour foamy and eventually lose its carbonation. If the beer has less pressure than the pressure applied, that gas will start to enter the beer, changing the flavor and texture!
There is an additional confounding factor, the same gas that keeps the carbonation balanced within the beer also propels the beer out the tap. It’s a pretty elegant system, as the pressure you put on the beer keeps the carbonation in while pushing it from the keg to wherever the faucet is. This means that the pressure we set on the beer not only affects how it tastes, but also how fast it pours.
Since most of the beer served in bars has a very similar level of pressure, many bar owners don’t concern themselves with the co2 levels of their beers. A professional will set up the system to pour those average beers at the right speed at the right carbonation, and there’s no more need for concern. That is, unless you want to be able to pour beers that don’t fit into that category and want to pour them correctly!
In the next article, we look at how to find the perfect pressure level for a given beer, and how they can be hooked up to a draft system and poured correctly.