by Lee Reeve

“How do you know how much alcohol’s in the beer when you make it?” is one of the most frequently asked questions I got as a homebrewer. The answer is, of course, gravity. No, not Sir Isaac Newton’s mutual attraction between any two bodies in the universe gravity; but rather, the term “gravity” that’s used in brewing and wine making. “Gravity”, or more accurately, “Specific Gravity”, is a number, a ratio expressing the density of wort to the density of water at various stages during fermentation.

It’s like this: before beer actually becomes beer, it’s just an unfermented malt-sugar solution called “wort.” Using tools such as a hydrometer or refractometer, one can measure the concentration of dissolved fermentable sugars in the wort. This specific gravity is called the “Original Gravity (OG)” and it helps predict the probable strength of the finished beer. To give you an idea of what kind of numbers I’m talking about: the specific gravity of water is 1.000 (specific gravity is unitless). Typical OGs for wort range from 1.035-1.055.

Once the wort has been “pitched” (that’s when yeast gets added to the wort), the yeast begins the process of fermentation, converting the sugars in the wort into ethyl alcohol and carbon dioxide gas. As the yeast breaks down the sugar molecules, the density of the wort drops (alcohol is considerably less dense than water). When fermentation is complete, another specific gravity reading is taken, this time called “Final Gravity (FG)”. Typical FGs usually hit around the 1.010 mark.

The percentage of alcohol in the wort-turned-beer is the calculated difference between the OG and FG, which indicates the amount sugar that was consumed during fermentation as well as the amount of alcohol produced. The average homebrewer relies on the formula ABV (Alcohol by Volume) = (OG – FG) x 131. So, for example, let’s say a beer had an OG of 1.045 and a FG of 1.010, then 1.045 – 1.010 = .035 x 131 = an ABV of about 4.5%

Gravity measurements are also sometimes used to classify the “size” of a beer. Beers that start out with lower OGs tend to yield ABVs in the 3.5-4.5% range and are commonly called “small” beers. Beers with higher OGs generally see ABVs in the 4.5-6% range; these are our familiar, “medium” beers. And then there are beers with remarkably high OGs, capable of pushing ABVs into the realm of 7-14% and upwards. These truly “big” beers are also known as “High Gravity Beers”, because their OGs can climb to levels in the 1.060-1.120 region.

Some of the more immediately recognizable styles of high gravity beers include: Barley Wines, Belgian Tripels, Doppelbocks, Imperial IPAs, Imperial Stouts, and Strong Ales. But a high gravity beer can be made from almost any style, provided enough malt and alcohol-tolerant yeast is used. They are inarguably the behemoths of beer, and not the sort of thing you want to be tossing back a few pints of and hope to remain standing.

And high gravity beers deserve the respect that they command. For not only do they require larger amounts of malt and specialty grains in their recipes, thereby making them more expensive to produce, but also because their higher alcohol content exerts higher stresses on the yeast during fermentation. They’re also much harder to make – both technically and aesthetically. (Homebrewers repeatedly share stories about lids being blown off fermentors when attempting to brew high gravity beers.)

But make no mistake– high gravity beers are not simply created with the goal of attaining stratospheric alcohol levels. For the brewer, they are crafted with long-term intention in mind and require months of conditioning, regularly needing years to mature. High gravity beers are meant to be sipped, their flavours and aromas appreciated, very much like fine wine, hence the reason why they are normally– and best– served in snifter and tulip glasses.

These beers all have extremely complex tastes and unique characteristics, which is why they are often paired with foods when drinking. Baird Brewing, whose lineup includes several high gravity beers, holds a yearly “Big Beer Weekend” event where they showcase their big beers together with a carefully selected menu.

And although high gravity beers are more likely to be seasonal releases, that doesn’t make them any more difficult to find. Thrash Zone in Yokohama offers almost exclusively “extreme” high gravity beers. Popeye’s in Ryogoku, with their recently expanded seventy beers on tap, is always guaranteed to serve more than a few. As a matter of fact, your favourite watering hole probably regularly carries one or two guest big beers. So, what are you waiting for? Why not go ahead make your next beer a big one?

Lee Reeve is a magician who publishes the beer blog
ABREWCADABREW – Magical Craft Beer from Japan.

This article was published in Japan Beer Times # () and is among the limited content available online. Order your copy through our online shop or download the digital version from the iTunes store to access the full contents of this issue.