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.
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!