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%
Step-by-Step Instructions for Reading a Hydrometer
How do you read a hydrometer...a question that is sure to have crossed anyone's mind who has embarked on brewing their own beer or making their own wine at home. 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.
Making calibration adjustments to the readings is where the fun starts! Below is a step-by-step guide to using a hydrometer to help you as you brew!
Step 1: Retrieve a Sample of Beer, Wine or Cider
Before retrieving a sample, be sure to sanitize the thermometer, hydrometer, thief, testing container and any other equipment that will come in contact with the fermenting liquid. Then, use a beer or wine thief to retrieve a sample of the liquid. The liquid should be at room temperature before taking a reading.
Transfer the liquid with the thief to a testing jar or a plastic graduated cylinder. You will need enough of a sample to allow the hydrometer to float freely once inserted into the sample.
Step 2: Insert Hydrometer into Sample
Place the hydrometer into the liquid. It should float freely without touching the bottom of the container. It is recommended that your hydrometer be centered and vertically positioned so it can depict the most accurate reading. If the hydrometer is leaning towards the side of the container, you can help center it by gentle spinning it in the liquid to allow it to center itself.
Step 3: Determine Original Gravity Reading
The increments of your hydrometer that you want to read are the specific gravity points. These will be listed as 0.990 and 1.000, then are abbreviated to say 10, 20, etc. You will be taking a reading at the level that the liquid rises to. (It doesn't hurt to spend some time getting acquainted with the increments on your hydrometer before taking readings as each hydrometer may be slightly different.)
To get the most accurate reading, read the bottom of the meniscus, or bottom of the natural curvature of the liquid. The meniscus will be level and not pulled by tension up the sides of the container or hydrometer itself.
The best way to read the bottom of the meniscus is to look at the hydrometer at eye level. If your liquid is darker, you may find it harder to read below the surface. If you are having trouble with a darker liquid, just be sure that you are reading from the same place (whether at the bottom of meniscus or slightly above) every time you take a gravity reading in order to keep your results and math consistent.
Step 4: Calculate Hydrometer Temperature Correction
Hydrometers are calibrated to read at a certain temperature, usually between 60°F to 72°F depending on the manufacturer. Your liquid does not have to be the same temperature as the hydrometer to get an accurate reading though.
If your liquid is a different temperature from the temperature the hydrometer is calibrated to, you will simply need to adjust the reading according to the instructions that came with your hydrometer.
This will entail checking the suggested gravity adjustments for the temperature of the liquid you are testing, and then adding to or subtracting from the SG reading according to the hydrometer instructions to get a more accurate SG measurement.
Step 5: Repeat for Final Gravity Reading
Repeat steps 1-4 once you are ready to bottle your homebrew. This will give you your final gravity with which you can then determine the alcohol content or ABV.