beekeeping equipment honey

Honey refractometers measure moisture content

Honey refractometers are used by beekeepers and honey packers to measure the moisture content of honey. Technically, refractometers measure the refractive index of a substance.

Explanation: Light travels at different speeds through different materials. The refractive index is just a comparison between two numbers: the speed of light through a vacuum and the speed of light through the material you are testing—in this case honey.

Light also changes direction after it passes through different materials. If you measure the difference between the angle of incidence (light coming in) and the angle of refraction (light coming out) of a substance you can use this number to determine the refractive index. This is how a refractometer actually works.

Explanation: If you look at a straw in a glass of water you will see it looks distorted. This is because light moves faster through just the glass than it does through the glass and the water combined. Likewise, light will move faster through honey that has few solids than it will move through honey that has many solids. In other words, the refractive index of honey will change based on the amount of solids (sugars and other substances) in it.

Refractometers also make corrections based on temperature, because the refractive index will change slightly as the temperature changes.

Now, to make this all the more perplexing, the amount of solids in a liquid is measured on a scale called the Brix scale.

Explanation: Brix is a scary sounding name for a simple kind of scale. Each degree of Brix equals 1 percent sugar. So, grape juice with a Brix of 18 is 18 percent sugar. The Brix of honey can be from about 70 to 88.

Now here is where confusion sets in. While most refractometers give a reading in Brix (solids in water), honey refractometers give readings of water in honey. This is (kind of) the opposite of Brix.

Explanation: This type of reading is used in honey refractometers so beekeepers don’t have to subtract the Brix reading from 100 to get the moisture level. It’s just a convenience. However, it can get really confusing when a beekeeper uses a refractometer designed for another purpose—such as brewing. Not only are these designed to be most accurate in other ranges, the readings are in Brix—not 100 minus Brix. It it best to use a refractometer designed for your specific purpose.

Once you understand how a honey refractometer works, it is simple to use. There are many variations in design, but these are the basic steps:

  • Calibrate the device with distilled or deionized water
  • Put a drop of honey on the prism
  • Close the trap door that flattens the specimen
  • Focus the eyepiece
  • Read the scale

Two things are especially important for getting accurate results:

  • Make sure the container of honey from which your sample comes is well-mixed
  • Take multiple readings, and average the readings

Explanation: Honey is a variable product which differs from hive to hive, even from cell to cell. And honey that sits for a while will have a different moisture content at the surface than at the bottom. So before testing, always make sure the honey is thoroughly combined.

Human error also plays a part. Sometimes a reading goes awry for no apparent reason and sometimes the scales are just misread or misunderstood. To be on the safe side, multiple readings are always a good idea.

One last thing: read the directions. All these devices come with detailed instructions which should be followed to the letter.

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    • The moisture content of honey must be about 16-18.5%. If the moisture is higher, the honey will ferment. If it is lower, the honey will crystallize.

      • Hi, Rusty, What can be done to avoid the extremes? Last year, my honey was above 18.5% and one suggested reason was from harvesting during the goldenrod season. The goldenrod has been around for about three weeks, or so, this year. Should I wait until it has stopped blooming? Chris

        • Chris,

          I don’t understand why harvesting during the goldenrod bloom would make any difference. If the honey is capped, it’s good to go and will be less than 18%. What reason did they give you for saying that?

          • He was just basing it on his experience that honey that had a large component of its source material from goldenrod could be too high in moisture. It sounds like you think that is unlikely.

            • Chris,

              The bees won’t cap honey until it is properly cured, no matter the source. So yes, I think it is unlikely. Perhaps the person accidentally extracted too many uncapped cells in with the capped ones. That would certainly shift the balance. The rule of thumb is never go over 10% uncapped, but I don’t like to cut it that close. I go for as few uncapped as possible.

              That’s the most likely problem, but perhaps there were others. But like I said, the bees won’t get it wrong, just we humans.

  • I have an RHBN-90ATC refractometer that says use dioptric oil to calibrate it. I am having trouble finding dioptric oil; can any one tell me where to get it, please? I hve tried e-bay buy seem only to get kits with refractometer and oil; I just want the oil. Can I use anything else?

  • When I try to measure moisture in honey on my handheld refractometer, there is no blue. What does that mean?

    • Same here — I calibrated it according to instructions, put the honey on it, and the field is now white, with no blue. I’m wondering if I have the wrong kind of refractometer.

        • I’m having the same issue. I think we’ve got the wrong refractometer. The scale is 0-30% Brix. I followed the instructions for calibration, and here’s why I think it’s the wrong kind of refractometer. Distilled water reads 0%, so it looks like I would be measuring sugar content with this scale — if it was a direct measure of water content, then distilled H2O should read 100%.

          BTW – The only labeling I see on the refractometer are the initials ATC.

          • Yes you have the wrong refractometer. Brix is the percentage of sucrose in a solution so it is telling you the sugar content of the honey. The Brix number in honey should be around 82%. (82% sugar + 18% water).

  • Your meter is measuring below the Brix of the sample. I use a meter with a 58-90 range. You might be able to dilute the honey (by weight) with water (by weight), do a little math and get pretty close using your meter but you are probably better off getting the right meter. If you choose to use the dilution method, it might help to dilute a sample of honey of a known Brix, dilute and measure the result and use that dilution ratio as a guide to measuring your honey. A reloading scale is probably accurate enough to do this and can probably be borrowed if you don’t have one. Another way to get to the same point would be to accurately weigh a precise quantity of honey and do a little math or comparison with that. Honey weighs about 50% more than water (a pint of water is a pound, a pint of honey is about 1.5 pounds). If you go that route, watch the temperature and the meniscus to get a precise volume measurement (warm honey is going to be easier to get a volume measurement from).

    • Irish,

      A beam of light changes directions when it goes through different substances. Read the directions for your particular fractometer to learn how to use it.

  • HI all,
    So – one can essentially “measure” both Brix and water content (moisture), with a simple refractometer scaled for honey? Example – the moisture content is 17%, thus the Brix value is 83? Simple math?

    • If there is too much moisture in honey, more than 17–18 percent, the honey will not keep but will ferment.

  • What is the best way to measure moisture with a refractometer?

    With crystallized honey?

    Or is it better to heat and measure while liquid?

    Thank you!!

    • Alfredo,

      I think it needs to be liquid for a refractometer to work correctly, but I’m not 100% sure.

  • I bought a refractometer and the instructions say to calibrate with distilled water. Their instructions show a completely different screen than is on mine. The instruction screen shows the label of salinity with 2 scales. One is d 20/20 which has a scale of 1.000-1.070 the other scale % and a scale of 0-100. It says to calibrate the water to 0. On my refractometer there are 3 scales one is 20 degree C Be and a scale of 38-43, bottom to top. Middle is Brix % with a scale of 58-90, bottom to top. The third scale is water % with a scale of 27.0-12.0, bottom to top. Since there is not scale for 100% water I cannot use their instructions. I have read that extra virgin olive oil has a brix of between 71 and 72. Is this an accurate way to calibrate the refractometer?

    • Venturadan,

      I don’t know anything about the brix of extra virgin olive oil or how much it varies, so I can’t say.

    • It’s hard to handle honey that is too wet. Is there a lot of it? If there’s not much, you can keep it in the freezer or refrigerator. Or you can save it for bee feed.

      More important is to figure out what went wrong. Did you extract a lot of uncapped cells? If more than about 10% of the cells are uncapped, it’s easy to run into problems.

  • @VirginQueen

    Hi. For first , excuse me for my bad english.

    For honey with too water inside you can use an electric dehumidifier: In a little clean* room (20-25 °C) place your opened honey tank covered by clean cloth and the dehumidifier. Wait 2, 3 or 4 days and use your refractometer for control.

    If it doesn´t work, Rusty idea is a good way

    Best regards.

    * Without bad smells !!!!

  • Hi Rusty,

    What is the best Honey refractometer you can recommend?

    I am in Ghana and there is so much bad honey on the Market so I need a very good refractometer on recommendation to be testing before purchasing.

    Thank you!

  • I would go by Betterbee’s recommendation at which says to calibrate the device either using 99.5% anhydrous glycerin, available at drug stores in the skin care section to a BRIX value of 73 or using EVO Olive Oil to a BRIX value of 71.5. You then can analyze the honey using the percent water reading. I have a cheapo that has both the BRIX and percent water readings. As I understand it the BRIX measurement is essentially the inverse of the percent water calculation and is therefore reliable for calibration even though we use the percent water analysis as the standard for honey.

    • Racheal,

      A saturated sugar solution contains as much sugar as can dissolve in a given amount of water at a given temperature. Honey is basically a saturated sugar solution containing mostly sucrose, glucose, fructose, and sometimes some maltose or other sugars. So I guess the answer to your question is yes, although I get the feeling that what you asked is not what you meant. Not sure.

  • Answers to some of the questions above: The RI of olive oil is about 1.468, the equivalent of 71 Brix. For better accuracy, you can purchase certified refractive index oils from scientific supplies.

    The correct oil for calibration appears to be 1.4875 (78.8 Brix)

    Cargille scientific is a major supplier of refractive index oils, just google Cargille refractive index liquid. I don’t think they make a 1.4875 but they do have 1.4880 which will read 79.0 Brix.

    Refractometers measure the angle of total internal reflection at the interface between the sample and the prism usually made from high index glass in cheap refractometers and sapphire crystal in good ones. In an optical refractometer with a blue contrast field, the field disappears when total reflection starts so the line between them corresponds to the RI. In a digital refractometer, a CCD is used to capture the angle.