The Care and Feeding of a Hydrometer

A hydrometer is one of those pieces of equipment that every beginning brewer should own and should know how to use.  Unfortunately, however, it is the one thing that often gets forgotten in those nascent days of brewing.  This wonderful little device was discovered by Hypatia of Alexandria in the golden years of discovery just before the beginning of the dark ages and has been used for hundreds of years in the brewing and wine industries

Hydrometers have three main components: The float, the neck, and the scale situated inside that is used for measurement.

Inside the neck of the hydrometer is a scale calibrated to one or more systems of measurement such as Specific Gravity (beer), Plato (beer), Brix or Balling (wine).  Some hydrometers have multiple scales such as in the picture showing a Beer/Wine hydrometer that has Specific Gravity, Potential Alcohol, and Balling scales.  Some of the more expensive models will have a thermometer in the bulb so that the temperature of the sample can be taken as well. A hydrometer works by displacement, much in the way a ship floats on water.  If we were able to change of the water by making it thinner or thicker, the ship would float higher or lower respectively. Wort or Must is a liquid saturated with sugar, the more sugars the thicker the liquid and the more it displaces the hydrometer.

When using a hydrometer there are a few things to remember:

  • Work with cooled samples: The liquid sample should be as close to the hydrometers calibration temperature (usually around 68oF) as possible.  If you are working with hot liquids, let it cool below 120o F before putting the hydrometer in the sample jar.  Rapid changes in temperature could cause the glass to crack or burst.
  • Be Accurate: Most hydrometers come with a calibration table to show you the change in specific gravity due to temperature, allowing you to sample somewhat hotter samples
  • Always work in the sample jar:  Never use your hydrometer in the boil kettle, bottling bucket or fermentor.  Contamination issues aside, the float is weighted with lead and that would not be a good additive for your hard earned beer or wine.
  • De-gas your sample: The bubbles in a partially or fully fermented sample can give you a falsely high reading.  De-gas with agitation or letting the sample sit for 20 – 30 minutes
  • Properly dispose of your sample: Unless the wort is still boiling the sample never goes back from whence it came.  This practice opens the beer or wine to infection and could potentially ruin the batch.
  • Always take the reading at the same place:  The preferred place to take a reading is at the bottom of the meniscus.  The meniscus is a “U” shaped depression caused by the liquid clinging to the side walls of the hydrometer and the sample jar.

This is simple device can increase the accuracy of your brewing or wine making, allowing you to attain the quality that you want.  Come into Kettle to Keg and see Jesse, he will help you pick the Hydrometer that’s right for you.

Hydrometer? Refractometer? What are they?

If you brew beer or make wine then you know that most everything we do is done to get fermentable sugar out of grain or fruit. We do this all just to give it to some hungry yeast in order to achieve our final result – alcohol!  This brings us to measuring those sugars, which we do to monitor the process and scientifically assess the health of the fermentation, as well as determine the strength of the final drink.  Fortunately we have some tools to provide that information, and they are so simple to use that no homebrewer should be without them.  There are a few scales that you should be aware of:

Brix: Used primarily in the wine industry.

Plato: Used by most professional brewers.

Specific Gravity: used by home brewers and some brewing professionals.

Balling: A measuring system used by vintners that has since fallen by the wayside.

There are many other industry dependent scales but we will be talking about the ones applicable to beer and wine. The two main devices used by home brewers are:

The Hydrometer

The simplest of all the devices, it was invented by Hypatia of Alexandria in the days before the dark ages fell and threw science back a thousand years.  A hydrometer measures the amount of sucrose in a liquid. The higher the amount of sugar per unit of liquid the higher the number will be on the scale.  The typical hydrometer consists of a weighted bulb at the base and a stem at the top.  Inside the stem is an insert with a scale showing Specific Gravity, Plato, or Brix, with sometimes Potential Alcohol as well.  The scale most homebrewers use (generally) is specific gravity, and it runs from .990 to 1.160.The Refractometer

A refractometer measures the sucrose content of a liquid by the liquid’s ability to bend a ray of light through a prism. These take only a drop of wort or must and are in some cases automatically thermally corrected.  Refractometers measure in Brix and/or Specific Gravity with only a drop or two of wort or must placed on the lens.


Both devices require calibration, for the hydrometer the testing jar should be filled with distilled water at 68 degrees.  If the measurement is more or less than 1.000, then note should be made for future brew sessions to adjust the reading by the degree of change.  For the Refractometer, a drop of distilled water is placed on the lens, the cover is closed making sure there are no air bubbles or dry spots.  Look through the lens and adjust the calibration screw till the scale is at zero Brix (or what ever scale it has in it).

The Pro’s and Con’s

The advantage of a Refractometer is the ability to analyze the liquid despite its temperature at anytime over the course of brewing.  The advantage of the Hydrometer is its cost, and ease of use.  Also once there is alcohol in the liquid the Refractometer needs a calibration table where as the Hydrometer needs a calibration table based only on the temperature of the liquid involved.

At Kettle to Keg we carry both Hydrometers (in many styles) as well as Refractometers – and if you need help learning how to use them we have knowledgeable staff on hand to help you!  With a little practice you can have a big impact on the quality of your brewing.