The Measurement Shop's Guide to Brix Refractometers

Refractometers are versatile tools that have a wide and varied range of uses, but for now we’re going to focus on using a refractometer to measure sugar content. These instruments are known as Brix refractometers, although they can also be known as a Brix meter, sucrose refractometer or sugar refractometer also. Before we go any further, let’s take a look at the Brix scale itself.

What does a Brix refractometer measure?

A Brix refractometer is used to measure sugar, but what does it actually determine? Well, it is the amount of solid sucrose matter that can be found in a given liquid solution, where one degree Brix is equivalent to 1 gram of sucrose in 100 grams of solution. It works by taking the refractive index (nD) – a measurement of the degree in which light changes direction when shone through a liquid – and correlating this value with the corresponding Brix measurement. The greater the amount of solid dissolved in the liquid solution, the greater the bend of the light will be and therefore, the higher the refractive index.

Why do I need a Brix refractometer?

It can be tricky to navigate the world of refractometers if you are buying one for the first time. To make this easier, let’s look at how Brix refractometers can benefit specific industries. It is valuable to note that there are far more industries that use Brix refractometers than the ones listed below.

Brewing – A refractometer is a common tool in beer brewing, although the Brix measurement is not really used. Instead, brewers want to know the specific gravity reading of their wort, which allows you to make a prediction of the ABV (alcohol by volume). The actual specific gravity value refers to the density of that liquid in comparison to regular water.

Wine Making – Using a Brix refractometer for winemaking is essential for knowing the correct time to pick your grapes. The Brix scale can help to determine the sugar levels of your harvest, which in turn can alter both taste and alcohol volume. A second device, known as a hydrometer, can be used to measure sugar content in wine and beer, although this requires a much larger sample than a typical refractometer. Just a few drops are necessary with a Brix refractometer and you have the freedom to walk your vineyard and accurately test your harvest as you go.

Honey Production – For beekeeping, instead of the traditional Brix measurement, the moisture content is preferred. If you imagine that Brix measures the solid matter in a liquid, then the moisture content measures the water content in the honey instead. This value is crucial for beekeepers as it gives insight into the honey’s ability to stay fresh over time. When purchasing a refractometer this is important to note, as buying the wrong kind of refractometer will make for some confusing results.

Jam Production – For jam production a refractometer assesses whether the jam is ready. Generally, a finished jam, jelly, marmalade or preserve will have a Brix rating of around 60% to 70%.

Fruit Production – Knowing the Brix measurement of fruit and vegetables is crucial for large scale farmers and small backyard gardeners alike. Measuring sugar content within your desired crop will give you an indication of the maturity and sweetness levels, allowing you to make informed decisions through the growing and harvesting process.

How to calibrate a Brix refractometer

Calibrating a Brix refractometer differs depending on whether you have a digital or analogue device, although the process is quick and simple for both:

Calibrating an analogue Brix refractometer

Begin by using a pipette to place 2 to 3 drops of distilled or purified water onto the glass prism and ensure that there are no dry spots or air bubbles. Pointing the refractometer at a natural light source, look through the eyepiece and examine whether the reference line sits at 0. If it does not, simply adjust the knob at the top of the device – you may need a small screwdriver to do this depending on your device. To finish, wipe the glass dry using a soft and clean cloth.

Calibrating a digital Brix refractometer

Fill a pipette with distilled or purified water and place 2 to 3 drops on the surface of the prism. Make sure to shield the prism using your hand if you are calibrating in an area with a strong light source. Next, simply press the button marked zero or cal to begin the calibration process. After a couple of seconds your device should read 0 on the display signaling that the process is complete. Finish by wiping the water from the prism using a soft, clean cloth.

Will temperature affect my results?

Temperature is fundamental when measuring Brix and can change your results greatly, depending on the solution being examined. The desired solution temperature should be 20 ° C, so it’s important to let any sample cool before placing your drops on the device. Only a few drops are necessary, so it should not take long for your solution to cool – around 10 to 15 seconds, depending on the temperature. Some Brix refractometers now come with automatic temperature compensation (ATC) which means you won’t have to waste time looking at temperature correction charts.

How to use a refractometer to measure jam

This is a method for using an analogue refractometer for jam, although the method is generally the same for all solutions.

• 1: Place a small amount (around 30g) of jam/marmalade into a beaker and mix well in order to produce a testing sample.
• 2: Once mixed, open the refractometer cover and apply 2 to 3 drops of jam onto the refractometer prism surface.
• 3: Close the plate/cover and ensure that the jam sample is evenly spread over the whole surface of the prism.
• 4: Look through the refractometer eyepiece and record the value where the dark and light measuring bars meet – this is the Brix percentage value.
• 5: Once you have taken the Brix value, clean the prism using a damp tissue to remove all sample residue.

Things to consider and useful tips:

• This process may differ depending on whether you use an analogue or digital refractometer. Therefore, you will need to ensure that you are following the correct procedure based on the type of refractometer.
• Refer to a Brix value conversion table appropriate to the sample you are testing when measuring results.
• A recommended ratio of fruit: sugar is 1:1, however this will differ depending on the amount of pectin within the fruit.
• The setting point for jam is 105° C (220° F). When starting the jam making process, attach a sugar thermometer to the side of a saucepan, placing the end into the jam mixture. When reaching the temperature above, the jam solution should set.

Brix to refractive index conversion chart