I’ve been playing around with the pressure that I have my Guinness kegerator set to. From my homebrew days I know that I tend to prefer a lower pressure for most beers. I find that it adds to the perceived creaminess of a beer as well as causing less bloating. I’ve had my nitro regulator set around 34 PSI with a 75/25 blend of Nitro/CO2. I’ve been enjoying the pours but in an effort to keep dialing in my Guinness I decided to try a higher pressure.
How Did I Determine The Pressure
I mainly used three tools to determine the pressure:
The first step was trying to find the target carbonation for Guinness. I could not find anything official. According to this Brew Your Own article, Nitrogen beers are generally served with around 2.4 g/L of carbonation. Guinness may aim for slightly higher or lower, but considering that it is the benchmark for nitrogen beers, 2.4 g/L is probably pretty close. And my nitrogen regulator is analog so it’s not like I would be able to dial in to a very specific PSI.
The next step was to figure out how to get 2.4 g/L of carbonation. For this, I used the McDantim EasyBlend app. Click on the Pressure tab and you’ll need to supply the following variables:
- Temperature (in Celsius)
- Altitude (in metres)
- Alcohol Content
- CO2 content (in g/L)
- Blend (CO2 percentage)
I keep my kegerator at 42 F. I’ve used an Aranet4 to record the temperature and I’ve found that the compressor turns on around 44 F and shuts off around 42 F. And while some of the areas of the kegerator can get a little warmer, it mostly stays around 42 F. According to Google, 42 F is 5.55556 C. So I used 5.5 for the temperature.
Altitude is a little tricker. You could Google the altitude in your town but it could be way off from the altitude of your specific location. Luckily, for our calculations altitude does not have a large impact to the result. Still, I wanted to be accurate. This is why I downloaded the My Altitude app. It estimates that my altitude is 35.44 metres ± 30 metres. I’m going to use the 35.44 number.
The rest of the variables are easy. The alcohol content of Guinness is 4.2%. The CO2 content is your target carbonation. Based on the Brew Your Own article I referenced above, I used 2.4. The Blend is what percentage of CO2 your are using. I use 75% Nitro so for this number I plugged in 25.
The Result?
2.71 bar. Asking Google for 2.71 bar to PSI I find that I want a target carbonation of 39.30523. So for the last third of my current keg, I’ve decided to up the pressure on my regulator to somewhere near 39.
Early Results
I changed the pressure about 48 hours ago and had a few pours today. I can’t do an A-B comparison but the higher PSI definitely results in a larger head. In some cases it goes into the strings on the harp. I haven’t noticed much of a change in the perceived creaminess. The overall taste seems to be closer to what I’d consider to be “normal” for Guinness. Originally, I thought that the roasty, chocolate notes were more prominent. But I think that was just due to the beer getting warmer. I do feel like the higher PSI results in more bloating. But all of this could be in my imagination. The higher PSI does seem to lead to a visual difference. The beer with the higher PSI has a larger, less uniform head; with more bubbles appearing in the foam. I’ve also noticed a lot more condensation around the draft tower and faucet since I increased the PSI. But I’m not sure how these could be related since the pressure should only impact the beer in the line. I assume it has more to do with the local weather. I will probably drop the PSI back down for my next keg. But I’ll keep this one at 39 until I finish it.