Making beer is an intricate process of surprising complexity. It involves elements of chemistry, biology, engineering, hydrology, calculus, and a whole other slew of disciplines that you’d have trouble sitting thru in any college classroom. Thankfully we have brewers—modern day alchemists—who sift through the tedium to produce something as simplistically magical as an ice cold brewski.
If you happen to glance at the technical specifications accompanying most beers, you will sometimes notice all sorts of measurements that might not make any sense to the layperson (non-beergeek). Most people are familiar with the ABV—alcohol by volume, is a very straight-forward reading of what percentage of the libation is pure alcohol. Most spirits sit at or around 40% ABV, wines hover near 12%, and your standard beer is probably just below 5%.
That part is easy to understand. But you might also notice a number that has a ‘degree’ sign next to it. Now you’re starting to get scientific. This number is a representation of the ratio of fermentable sugars to water as measured by the ‘Plato scale.‘ Using a specialized hydrometer, brewers measure the density of their wort before fermentation begins. Wort is essentially sugar water that will turn into alcohol once yeasts have been introduced to convert that sugar into booze. The number of degrees Plato corresponds directly to the percentage of extract, by weight, that is present in the wort. For example, if it’s 10 degrees Plato, sugars account for 10% of the wort’s weight.
Why does any of this matter to a typical beer drinker? Well, the calculation is essentially a reading of how much malt is present in any given beer. If you prefer a mellow stout or English style ale you’ll probably enjoy a beer that has a relatively high specific gravity (more maltiness) so that it outweighs the perceived hoppiness. If you’re more a fan of bitterness, chances are a lower degree of Platos will suit your fancy.
Sometimes brewers will show the density of their beer before fermentation using a measurement of original gravity (O.G.s). This number will change during the fermenting process as sugars are converted into alcohol, leaving you with final gravity. The difference between the original and the final gravity gives you an idea of a beer’s apparent attenuation. And, unless you plan on opening your own brewery sometime soon, these data are wholly useless. Although hopefully you’ll do a little bit better on Jeopardy! if ‘The Science of Beer‘ ever comes up as a category.