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In the last post we went through the entire boil, pitched the yeast and moved our wart to the primary fermentation vessel. Within a day or so you should begin to notice the beginning of the fermentation process. As the yeast converts sugars into CO2 and Alcohol, pressure will build in your fermentation vessel and some of the CO2 will “burp” out of your airlock as seen in the little video above. Beer is being made! Great success!

Now it's time to get a little nerdy... One thing I did not mention is that a sample of the beer should be taken just before pitching the yeast in order to measure specific gravity (SG) with a hydrometer.

A hydrometer is an instrument that measures the density of a liquid in relation to water. This is done by floating the hydrometer in the liquid and reading how deep it sinks in by looking at where the scale on the top just breaks out of the liquid. Water has a specific gravity of 1.0.


Why is this important to the brewing process? At the end of the boil you have a liquid solution that is much denser than water because of all the dissolved malt. A measurement should be taken just before pitching the yeast. This measurement is called the Original Gravity (OG). While the OG of beer can range from about 1.02 to 1.16 (meaning 1.02 – 1.16 x denser than water), you will always be aiming at a much more narrow target that is provided by your recipe or at least confined by the general guidelines for the style of beer you are making.

Hydrometer floating at 1.068:

Now that you have both an OG and an FG reading, you can calculate your beers alcohol content! This is done by following this simple equation.

(Original Gravity – Final Gravity) x 129 = Alcohol by Volume%

My OG measurement came to 1.068 while the temperature of the beer was around 75 degrees. Since the hydrometer is calibrated for 60 degrees I have to adjust by about 2 points (this will be displayed in a chart that comes with your hydrometer) making my actual OG around 1.07. This is right around where I wanted to be for my IPA as that style ranges from 1.055 to 1.07. I do not have my final gravity reading yet because my beer is still racked, however it should come out to around 1.016. So the calculation would work out as follows:

(1.07 – 1.016) X 129 = 6.96% ABV

It is kind of fun to take these readings throughout the process because you get to see how your beer is coming along and how your yeast is performing. It is also great to drink your samples after, which will immediately bring all your senses back to the day of the boil. Moving to secondary fermentation vessel is next- it is tasting awesome so far and I cannot wait until it is done!