Step 4: Gravity, oh gravity

So, we selected our beer and we mixed all our ingredients. Periodically, however, we also need to check and see how the fermentation’s going. There are a few things that must be done while your beer is fermenting, ensuring that things are going…”smoothly”…

Here’s the fermenting vessel.  Nothing too special about it, except for the little trap at the top that contains water.  The main purpose for the trap is to show carbon dioxide bubbles escaping from the vessel to the outside of the bucket.  If you didn’t have an escape mechanism for the CO2, then you’d blow the thing up in your basement!  But more importantly, as long as you see bubbles, you know  your yeast is making CO2, and consequently, alcohol.

Here’s what your beer should look like, with a nice foam called krausen. This picture was only a few days post-start of fermentation. There should be a few inches of krausen on top of the beer.

You can use a “thief” to remove a relatively small volume of the beer for testing with limited introduction of contaminants to the brew. You could do this with a ladle or anything else, really, but this little guy is well-suited to removing beer and adding it to…

…another vessel that you can test with your hydrometer. The hydrometer is what you use to calculate the alcohol content of your beer, or wine, or whatever. It does this by measuring the density of sugar in a liquid. Since our beer started out as mostly sugar, that means it started at a relatively high “specific gravity,” in this case, 1.050. As the week(s) draw on, the yeast break down the sugar producing alcohol and CO2, thus the specific gravity will decrease as fermentation continues. There’s also a percent alcohol scale on the side of our hydrometer, so you can measure that, too. However, specific gravity is a calibrated system, so you can make adjustments to your numbers based on the temperature the beer was measured in.  It’s very easy to use, basically just pouring beer into anything (like the tube it comes with, but a glass of beer would work, too) and allowing the hydrometer to float in it.  There are markings on the side of the hydrometer that you read, like a thermometer scale, at the point where the hydrometer exits the beer.

I’m posting this after I checked it for the last time and I’ll go ahead and tell you that it ended at a specific gravity of 1.011. You can run these calculations yourself, generally by subtracting the last one from the first one. Alternatively, you can find a nifty website to do it for you. The numbers off the calculator come out pretty close to what my hydrometer told me: ~5% alcohol. The calculator, however, also estimates that each 12 oz beer will have ~170 calories.

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