What is a Refractometer? | How Refractometers are Helpful Across Multiple Industries

In a previous blog, we wrote about how one of the Terriss team members got to take a look around PittCon 2024.  While there, we saw a familiar name in the form of Xylem Lab Solutions.  They were showcasing their products at a booth, with the refractometer as the star of their demonstration.

Terriss also carries refractometers, from bench top to handheld, and we thought we’d explain them a little more using this blog.


A refractometer is a device or instrument that measures the concentration of a solution by the angle of refraction of light.  However, to further understand refractometers and how they work, we need to delve a little deeper into some relevant terms.


When light bends as it passes from one transparent medium to another.

Refractive Index

Refractive Index is the ratio or velocity of light as it goes from passing through no medium to passing through a medium.  That is, it is the change of the speed of light as it passes through a vacuum to a medium.


Solutions have different refractive indexes depending on the concentration in the water. By observing the refraction in a solution, based on the chosen scale, a user can determine the concentration of the solute within the sample. Thus, a refractometer measures the concentration of solids or solutes in a sample.

How Does Refraction Work?

When light travels through a liquid at an angle, it bends – or refracts.  It slows down and changes direction as it travels through a new medium.  This phenomenon can be use to measure the concentration of a liquid solution, since light refracts more when traveling through suspended solids.  The refractive index can thus be used to assign a value.

What is a Refractometer Used For?

A refractometer is used across a variety of industries.  Some notable industries include food and agriculture.  In the food industry, refractometers can be used to measure the concentration or sugar content of samples from grapes or drink mixes. It can also be used to measure the salt content of solutions like brines.

On the other hand, refractometers can be used in agriculture to determine the water or moisture content of liquids like honey or milk.

In manufacturing, refractometers can be used to determine the composition of substances, control dilutions, or to check the purity of a substance.


Our Terriss team member who attended PittCon came back with some notes on how to use a refractometer, specifically from the Xylem Lab Solutions’ demonstration. Below is a step by step instruction on how to generally use a refractometer; however, each instrument might be a little different and it is always important to refer to the actual machine’s operation manual.

Going by the instructions from the demonstration, however, here’s a general gist of the steps!

  1. Check to see if the prism or well is clean.  If not, use a pipette to drop lukewarm water into the well.
  2. Close cover plate or pressure foot.  Ensure that the water is spread across the prism.  Check reading to ensure that the reading is 0 or calibrate so that it reads as such.
  3. Remove/open cover plate.  Dry using lint-free tissue or towel.
  4. Using a clean pipette, drop 1 to 2 drops of the testing solution onto the well/prism.
  5. Close the cover plate/presser foot. Ensure the sample is spread across the prism.
  6. Press OK and allow for the refractometer to measure the sample.


Check out the variety of refractometers and other related products on our website.  If you want more details, give us a call at (732-988-0909) or email us at orders@terriss.com.

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