One of the fundamental measurements related to brewing is the gravity of the beer you are making. The gravity or “specific gravity” of the wort will change during the brewing process as the yeast ferment the wort into beer.
Before the yeast start to produce alcohol, the gravity, or “Original Gravity” of the wort is mostly a measurement of the presence of sugar in the liquid. This number will give you an idea of the amount of fuel that the yeast have to work with in changing your wort into drinkable beer and make it alcoholic in the process. After the fermentation is complete, most of the sugars are used up and there is considerably more alcohol in the beer. At this stage, you can take a “Final Gravity” reading to determine the amount of work the yeast did and the amount of alcohol that they put into the beer by doing that work. Pretty cool!
Most of the time, the gravity measurements are taken using a floating hydrometer. This device is basically a glass tube that has some led in the bottom of it to make is sink. The hydrometer, when dropped into a sample, will sink to a point and stop. The line that the liquid hits on the scale on the side will give you your gravity reading. Generally you have to offset it based on the temperature of your sample but generally it is not that much.
So, now when you go to the corner store and see the 40oz bottle of Steel Reserve High Gravity Lager, you know what they are talking about. Basically, it is some cheap beer that has a lot of alcohol in it.
Cheers!
