So...finally have these things going...hopefully I'm using them correctly
Homebrew 101: So, is that a hydrometer in your pocket or….
November 26, 2014
There are allot of intricacies to ensuring that specific qualities of a beer come out the way that they are intended. So far in this series of posts on the blog we’ve seen that temperature can affect taste and color, yeast strain can affect sugar content as well as fermentation and sanitation practices can impact nearly every quality of a homebrew. While these are all important we have yet to review the one part of brewing that many consider the most important: alcohol content. We all know where this essential component comes from (if you don’t, you should read the Homebrew 101 on yeast…..for serious) so this time around we are going to review how to use a hydrometer to find out just how much of it is in your homebrewed goodness.
What’s a Hydrometer?
A hydrometer is a relatively simple instrument used to measure the specific gravity, in our case that of wort/beer. Most look like a glass thermometer with a weight on one end and several sets of numbers along its stem (it’s the science-y looking thing in the picture up there). Hydrometers are used for more than brewing and have applications in everything from measuring the charging capacity of battery acid to the density of table cream with different measurement techniques and methods for each. I’m not going to go ultra-nerd and explain the science behind it, but if you are so inclined the principles of physics that are at work with this nifty little doo-dad are pretty cool.
How do you use this thing?
As foreboding as the thought of using the kind of equipment you saw in high school chemistry for making beer might be, breaking out the hydrometer is actually one of the easier parts of the brewing process. That being said there are some things you need to do to make sure it’s done correctly. In addition to the hydrometer, it’s also highly recommended that you pick up a graduated cylinder. This can help ensure the volume of beer/wort being used to test is consistent and allows for a more accurate reading of the hydrometer itself. Like allot of new brewers when I first started to measure the specific gravity of my brews I just used the tube in which the hydrometer was sold and found that would often stick to the side and make it hard to get an accurate reading.
So, in order to find out how much alcohol you have you need to measure the change from the time you first cool your wort and rack to primary to the time you are finished with fermentation. First, rinse your graduated cylinder and gently place the hydrometer inside. After cooling your wort, take a sample equivalent to ¾ of the total volume of your graduated cylinder and tap the side to get any air bubbles out. Write down the specific gravity level at the lowest point of the meniscus (the curve that is at the top of the liquid). The scale ranges from 1.00 (which is what distilled water should be) and generally top off at 1.50-1.75. Initial gravity readings for wort are usually slightly higher than the 1.00 baseline for water (i.e. 1.04 etc). Depending on how manic you want to be with your brewing, you can take samples each day during the fermentation process to see when it levels off (a standard practice at many larger breweries with bio-chem folks on staff) or if you are more of a “sit back and let it do its thing” kind of brewer you can take a measurement at the end of each fermentation stage.
Figuring out your ABV
I’ll warn you now, this part involves a wee bit of the maths. When you are ready to figure out how much hair your brew will put on your chest you will need your Original Gravity ( this first reading you took from the wort) and your Final Gravity ( the last reading taken after fermentation). Subtract the final gravity from the original gravity and multiply that value by 130 and poof you have your ABV. If you are wanting to measure alcohol by weight, simply multiply your ABV by.814.
Ok folks, there is your simple but long winded explanation of finding out the alcohol in your beer. So whether you are measuring your own brewing creation or one-uping your friends with a wee heavy, remember that a little math and science can give you allot of bragging rights. Cheers everyone!