Measuring Specific Gravity
The Specific Gravity, or 'SG', is a key measurement in tracking fermentation and assessing when it is complete and your beer or cider is ready for bottling. The ABV of your brew can also be calculated by using SG readings. The most commonly used tool to measure SG is a 'Hydrometer'. A hydrometer is included in our Starter Kit and is also available for purchase separately.
The standard gravity readings on a hydrometer are denoted by numbers, starting with 1.000, and incrementing by .010, .020, .030, and so on. These numbers represent 1.010, 1.020, 1.030, and so forth.
The point where the liquid level meets the hydrometer scale is your reading. For example, if the brew is at the spot where the arrow is pointing on the hydrometer below, your reading will be 1.040.
To take an ‘SG’ reading using a hydrometer:
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Pour a sample of your brew into a trial or test tube and float the hydrometer in the tube. Be sure to fill the sample tube with enough liquid to float the hydrometer in the tube.
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Spin the hydrometer between your thumb and finger to remove any bubbles attached to the glass of the hydrometer that could distort the reading.
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Take the reading where the liquid meets on the hydrometer and keep a record of this number.
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After taking your reading, discard the sample and be sure not to pour it back in your fermenter.
The alcohol by volume (ABV) of a beer or cider is also determined by taking SG readings. To calculate the ABV, you need to be sure to take two SG readings – one at the start of fermentation (original gravity [OG]), and once at the end of fermentation (final gravity [FG]).
Your ABV should be very close to the figure indicated on your kit, however, for an even more precise figure, you can use our ABV calculator, below: