Beer Hydrometer Use 101: Tips, Tricks & Pointers

A hydrometer is a useful tool that will save you many headaches—and many batches—down the road. Incorporate it into your process, and your batches will only continue to get more consistent  and better with time. We will walk you through the process, give you tips for ensuring accuracy, and items of consideration when selecting a hydrometer.

For beer, you will likely be using a Brix or Specific Gravity Hydrometer. First, let’s walk through how to properly clean and use your hydrometer:

1. Assemble and Clean Your Supplies:
Before you begin, you will need a hydrometer, a cylinder or test jar, your sample and what you’re using to collect it and your method for recording your results. You will need to ensure your sample drawing apparatus, hydrometer and cylinder/jar has been properly cleaned and sanitized. Obtaining accurate results and creating the desired finished product are dependent on there being no contamination in your sample. Using a good cleaning agent, be sure to thoroughly remove any visible dirt or debris.Once clean, dip in the sanitizer and allow to air dry. Glass hydrometers are fragile and break easily, so be sure to use caution or a hydrometer stand to prevent yours from rolling off the counter as soon as you turn around.

2. Draw a Sample and Test:
Draw a sample and carefully pour into your cylinder or jar (see tips below!). Be sure to account for volume displacement of the hydrometer to prevent spills and ensure the jar is level.
Hold the hydrometer for the top of the stem - fingerprints will stick to glass and can alter the accuracy of the reading if you hold it further down. Gently lower the hydrometer into the jar, twisting gently to avoid bubble build up. Let go when it is approximately at a point of equilibrium. Take note of where it is currently floating. Gently grasp the hydrometer between your thumb and forefinger, and press it a few millimeters into the liquid and then release. The hydrometer should rise back up slightly and settle - you are now ready to take your reading. Note where the hydrometer emerges from the water. The liquid will appear concave where it meets the stem of the hydrometer (at the meniscus if you recall high school science class!). While viewing at eye level, you are looking for the plane of intersection of the horizontal liquid surface and the stem. The measurement on the scale is your relative density reading. Record your reading to easily refer back to it.

Tips & Pointers:

Watch out for Bubbles: Pour your liquid sample slowly and carefully down the side of the jar and stir the liquid gently to avoid the formation of air bubbles. These will move the position of your hydrometer and alter measurements by creating added buoyancy.

Contamination: If the meniscus is crinkled or dragged out of shape by the motion of the hydrometer it indicates either the hydrometer of the surface of the liquid is not clean. Carefully clean the hydrometer stem and remove any impurities on the surface on the sample.

Jar Selection: Your jar must be wide enough so the hydrometer won't touch the bottom or sides when it floats - this will obscure your measurements. Use any clean container like a graduated cylinder, however we recommended using a hydrometer jar – a tall round jar which ensures correct diameter to eliminate edge effects from surface tension, but narrow enough to not have to use too much of your sample. You should look for a jar with a wide base and a plastic cuff around the top that stops the jar from tipping completely sideways and breaking.

Temperature Correction: Hydrometers are calibrated  to test the density of a liquid at a particular temperature - which can usually be found marked on the stem. Temperature does affect density so if your liquid is not at that specific temperature, you will either need to allow it to come to temperature or correct your reading using a temperature correction chart or calculator. Here is a great temperature correction calculator: https://www.brewersfriend.com/hydrometer-temp/
For best results take a temperature reading both before and after using your hydrometer to ensure the temperature stability. Thermohydrometers can be very helpful in this regard, as they measure both temperature and relative density simultaneously.

Pointers to consider: Glass breaks, especially when you’re dealing with wet hands, so consider a plastic hydrometer. Do your homework when shopping online. Store your hydrometer in a sturdy case so to avoid breakage. You can also use your hydrometer jar to keep it safe from rolling.
Having a backup hydrometer on hand can be helpful. Always test your hydrometers in distilled water before you test your beer to ensure accuracy. Be sure to choose the right scale for your brew. You may come across the proof & tralle hydrometer,but it is designed for much higher alcohol solutions, like spirits and liquors. It is not suitable for beers or wines.

Photo Credit: @Barleythebrewpup on Instagram