I don’t care who you are or what you “look” at when you pick a beer. I know for a fact that you’re paying attention to the ABV. I know this FOR A FACT.
Everybody cares about alcohol by volume (ABV) to some extent. If I’m trying to relax in the afternoon, odds are I’m not going to be slamming half a bottle of 13% ABV barley wine. I might not even go for a 6% ABV IPA (total lie, I can drink an IPA any day of the week).
So, back on track – how is ABV measured in beer? Let’s learn!
The Nitty Gritty of Measuring ABV
Alcohol by volume is, by definition, measured by taking “the number of milliliters (mL) of pure ethanol present in 100 mL of solution at 20 degrees Celsius (68 Fahrenheit),” per Wikipedia.
Based on this, let’s get something clear: ABV changes. Depending on the temperature, the alcohol by volume of your beer could change – sure, it’s such a small amount that it’s probably negligible, but it still changes.
Other than that, nothing too special about measuring ABV in beer. Your local brewer makes the beer, bottles it, slaps a number on the label and tell you you’re drinking a 5.8% stout. Cool.
And never in a million years will that 5.8% change. After a beer is bottled, it’s locked in a suspended state, unaffected by the outside world…unaffected by time.
Not really, though. Guess what? The label that tells you the ABV is probably wrong, and governing bodies around the world know it.
If you didn’t want to waste your time reading that link, I’ll break down the interesting part: the US government accepts that a malt beverage (i.e. beer) can be within 0.3% off from what’s labeled. The EU is even more tolerant, letting alcohol be within 0.5% of what’s labeled.
Your beers are alive, and time makes them ferment. The time between when ABV is measured and when you drink it can be a while, and things can happen during that period.
Oh, and it could also be that a brewer doesn’t measure it properly. Fortunately, you can measure it yourself! But that’s for another post.