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.


3 thoughts on “Hydrometer? Refractometer? What are they?

  1. Refractometers are great for brewing, but I’ve had trouble with mine fogging up when brewing in my garage in the winter months. Also, if you’re grabbing an OG reading from the kettle after lautering be sure to stir well before taking a sample. Sratification could cause you to be misled.



  2. I would guess that the fogging issue is either due to some water vapor being trapped in the body when it was made or you have a small crack in your hydrometer and it should be replaced. The weight in the bottom is made of lead and you don’t want that in your beer.

    Good point about the stratification of the sugars.

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