If you’ve ventured into the wonderful world of homebrewing or winemaking, you will be using a hydrometer quite often. While using it may seem intimidating at first, once you have a basic understanding of a hydrometer, using it is a fairly simple and straightforward process. We'll start off by answering some basic questions about using a hydrometer and then outline the steps you’ll need to follow every time you use your hydrometer.
Q. What is a hydrometer and what is it used for?
A. A hydrometer is used to measure the gravity of, or the amount of sugars in, beer, wine or cider. Measuring gravity periodically as a batch brews allows you to monitor your fermentation more closely which can help lead to a better final beer, wine or cider. A hydrometer is calibrated to the density of water. By comparing the gravity of the liquid to the gravity of the water, you will be able to determine the amount of sugar being processed during fermentation. These gravity readings will also help in calculating specifications like alcohol by volume (ABV).
Q. Where can I obtain a hydrometer?
Q. How often will I be using a hydrometer during the brewing or winemaking process?
A. We recommend testing your specific gravity before and after fermentation at the very least. These readings are referred to as OG (original gravity) and FG (final gravity) readings.
If you are unsure if your brew is ready to proceed to a new step in the process, such as bottling or a second ferment, you can measure the brew once a day for several days to ensure fermentation has come to a standstill. This will be evident when the gravity reading remains the same for multiple days. When the fermentation comes to a standstill you are ready to move on to the next step in the process.
You can also check the gravity at different intervals during the brew process such as checking when racking into a second ferment, or when adding conditioners or extra fermentable sugars for bottling. Checking the gravity daily is not required, however, the more you check the gravity the more you will know about the progress of your beer, wine or cider. At the same time, keep in mind that taking gravity readings requires taking samples of the liquid which creates opportunities for contamination if sampling equipment isn’t sanitized properly.
Q. What does a hydrometer take readings of and what do these measurements mean?
A. A hydrometer will take readings that can be used to measure specific gravity, alcohol by volume (ABV), and brix.
- Specific gravity – Measures the relative density of liquids. By measuring the specific gravity, you can monitor how the fermentation process is going throughout the brewing period. The specific gravity of a liquid will decrease as the beverage ferments and the sugar content is reduced. Specific gravity readings will help you later to determine the ABV.
- Approximate alcohol by volume (ABV) – This reading gives a homebrewer an estimate of what the final alcohol content of the beverage will be.
- Brix – The Brix reading on a hydrometer measures the sugar content based on the beverage temperature.
Q. How do you use a hydrometer?
A. Using a hydrometer is a fairly simple and straightforward process. Making calibration adjustments to the readings is where the fun starts. Here are step-by-step instructions for using a hydrometer.
Q. Do I need to clean the hydrometer? If so, how do I clean it?
A. We do recommend cleaning your hydrometer with warm, soapy water after each use. Be sure to remove any debris from the hydrometer and testing jar. Rinse and allow to air-dry. Once you are ready to use the hydrometer again, you will need to sanitize the instrument as well as your beer thief, thermometer, and testing jar. You can learn more about using cleaners and sanitizers by reading A Guide to Sanitation for Homebrewing. For best results, please always follow the manufacturer's instructions for washing, rinsing, and sanitizing.
Q. Are there any pieces of equipment that are helpful to have to use with a hydrometer?
A. To use your hydrometer we recommend having a large testing jar or graduated cylinder to place your sample liquid in. The container should be tall enough to allow the hydrometer to float freely without touching the bottom. A beer/wine thief is also very handy to have around. These make retrieving a sample of liquid from your fermenting bucket much easier, and will not disturb the sediment or brew as much when taking samples.
Q. Do I need to calibrate the hydrometer? If so, how do I do this?
A. It is important to note that hydrometers are calibrated to be used in a liquid of a specific temperature. Some hydrometers are typically calibrated to 59-60°F, and newer ones can be set at 70-72°F. The temperature calibration for your hydrometer will be in its instructions. Each hydrometer will have specific amounts to increase or decrease your readings by to account for the temperature difference for your liquid.
Q. How do you calculate the ABV from my specific gravity readings?
A. There is a simple equation you can use to calculate the estimated alcohol by volume for your homebrews. On your hydrometer’s instruction sheet, there should be a chart listing the Approximate Percentage of ABV (APPROX % VOL) that corresponds to Specific Gravity (SP GR) readings.
Use the chart to determine the approximate alcohol percentage for both your Original Gravity (OG) reading and your Final Gravity (FG) reading. To determine the estimated ABV of your beer, wine or cider, subtract the Final Gravity’s approximate alcohol percentage from the Original Gravity’s approximate alcohol percentage.
OG: 1.065 = 8.6% APPROX % VOL
FG: 1.010 = 1.3% APPROX % VOL
Equation: ABV = 8.6% - 1.3% = 7.3%
Learn more about brewing beer at home by browsing our expert advice articles on homebrewing or shop our collection of beer, wine, and cider products to get started making beer, wine, or cider at home!