Why pressure barrels are important and how to get the best out of them.
One of the most frequent questions we get asked by novice brewers (and some experienced brewers) is, “why are pressure barrels and the ability to pressurise them with CO2 so important to the home brewer?” One common misconception is that injecting CO2 into a barrel is only to increase the beers head and sparkle. It is certainly true that a beers head and fizz is increased by pressurisation, but this not really the objective of pressurised by barrels. Their main purpose is to ensure that our beer stays fresh for as long as possible. At the start of drinking a keg of beer, the pressure within the barrel caused by the secondary fermentation, will likely be sufficient to push the beer out the tap at a fair rate. But once about half of the beer has been drunk the pressure within the barrel will have dropped considerably and the beer flowing out of the tap may slow to a trickle and if you’re not careful bubbles of air can be drawn into the barrel through the tap. At this stage there are two options: You can loosen the cap of the barrel to allow air to flow in and push the beer out of the tap. This is how ‘cask ales’ are served in pubs but this is not very convenient for the home brewer, as once air comes into contact with the beer, it is no longer a sterile environment and the beer will start to go off and leaving you with possibly twenty pints or more to drink in a few days. Not a problem if you’re having a few beer drinking friends around but otherwise this can be a challenge with undesirable consequences… The second option is to inject Carbon Dioxide into the barrel, this gives the pressure needed to give a good flow without compromising the sterility. Kept like this and providing the barrel was well sterilised to begin with, beer can last many months. For this reason it is also important to make sure that your barrel is well sealed with good o-rings and a liberal smear of petroleum jelly around the cap and seals, so that gas pressure does not escape and is wasted.