Sugar Refractometer : Quick and Dirty Guide

July 25, 2020

Sugar refractometer estimates sugar of liquids which has substantial concentration. The measure is expressed as ºBrix which means one gram sucrose per 100 ml solution. Therefore, a 23ºBrix reading equates to 23 grams sugar per 100 ml or simply 23%.

The reading is not accurate, the reason why I said “estimate.” The instrument measures soluble solid content which may include not only sucrose, but also acids and broken sucrose components, glucose and fructose.

The embarrassing moment

My first encounter with refractometer was a bit embarrassing. I was not alone though. All of my classmates felt the same as we thought of the same thing. And, that awkward moment turned into laughter.

We all arrived to conclusion — the small contraption was a monocular. It was a handheld device with adjustable eyepiece. Except, the lens which supposed to magnify distant images was odd. It was flat and slanted, forming a prism, with a cover. Perhaps, to protect the prism from dirt and scratches and breakage, due to accidental fall.

The eyepiece is indeed adjustable to suit individual vision. The prism and cover mechanism is for holding the liquid of concern.

How to use

Let’s cut to the chase and go straight to the real business.

  1. Wipe the prism and cover clean with soft cloth.
  2. Carefully drop liquid, enough to cover the prism area.
  3. Slowly lower down the cover to trap the liquid in between and check if the entire platform is covered. Repeat otherwise.
  4. Look through the eyepiece and rotate the adjustment until a clear horizon appears. Record.


Attempt to read Brix of distilled water. Adjust the horizontal line to zero by turning the screw which is usually located near the flap fulcrum. Distilled water should have a zero reading.


Things don’t always go the way you want. So, it’s time to tinker in case error occurs.

  1. If all that is seen is blue, the sugar concentration exceeds what the instrument can read. Acquire another that can read higher values. Juice refractometers can read only from 0 to 32 percent.
  2. If the sample on hand is honey or heavy syrup, get a refractometer specifically made for honey. Or,
  3. Do trial dilutions and compute the sugar content in accordance to dilutions made.
  4. For colored and heavy syrup, sugar estimation might not be possible due to low visibility. Again, try diluting the sample until the value becomes readable. Compute.
  5. On the other hand, seeing a white canvas indicates that something is wrong with the device. Re-calibrate. If unsuccessful, seek technical help.
  6. Observing black and other weird images signals a problem probably beyond repair. Bring it to service center, if there is. Buy a replacement otherwise.

Buying tip

Do your homework before throwing the hard earned cash. Read each instrument corresponding specification sheet and look for credible reviews if possible. A functional tool which is not fit for the job is a waste of money.

Role in food industry

The instrument plays a big role in food industry. Take wine for example. Before grape harvest, you can pick samples and quickly measure sugar content. It is convenient, prevents mistake, minimizes losses and leads to high quality product.

Another scenario is making syrup for leche flan. You test it by dipping in and raising up a spoon. The syrup is ready if a thread-like structure forms. You don’t have to trouble yourself with this if a refractometer fitted for the job is in hand. You just need few drops of liquid and bits of subsequent operations.

Focusing on repeatability while avoiding subjective judgements

Of course, a wine maker can quickly discern grapes of best quality without breaking a sweat. A chef may not even bother. Anyone could master syrup preparation after few trials. However, I am talking about quality and repeatability.

If you are running a winery or a sweet shop, you and your expert staff is not always there to do the right job. There will be times when the job needs to be delegated to someone else. A quality check without the help of instrument is always subjective. You and your co-workers are likely to interpret the set standards differently.

Refractometers are not only made for sugar measurement

There are variants for salt and wine and perhaps other substances too that I haven’t heard of.

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