How to Use a Refractometer for Measuring Sugar Content

Refractometers are a great tool to help determine the amount of sugars in your fruit. Typically, these units are used for measuring grapes, but can also be used for other fruits, and can be used similar to a hydrometer.

What Does A Refractometer Do, and How Does It Work?

A refractometer allows the winemaker to figure the percentage Brix (the relative “sugar weight” of a sample compared to distilled water) of the juice of grapes or other fresh fruit. Brix is sometimes referred to as Balling - don’t worry, the terms are interchangeable. Depending upon the readings observed, a winemaker can monitor the progress of ripening and adjust their plans for harvest, if necessary. In simplest terms, the refractometer works much like a prism.

Remember how, as a child, you could use a prism to separate out the different wavelengths of light (red, orange, yellow, green, blue, indigo, violet) when a source of light was shone on the prism at the correct angle? Well, the modern refractometer works on the same principle - it reacts differently to light (by giving a reading on a scale) depending on the amount of sugar that is available in the liquid sample held between the daylight plate and the main prism assembly.

How to Use a Refractometer

  1. Place several drops of the sample liquid on the angled prism.
  2. Seal the clear plate on top of it.
  3. Look through the eyepiece while pointing the refractometer at a source of direct light. (Do not look directly at the light with the naked eye!)

NOTE: Refractometer readings taken after fermentation has begun read higher than they actually are because of the alcohol present. To negotiate this issue, use a Refractometer Calculator to make conversions.