Refractometer
Lexikon
A refractometer is an optical measuring device with which beekeepers can determine the water content of their honey themselves without having to send a sample to a laboratory.
A refractometer is an optical measuring device with which beekeepers can determine the water content of their honey themselves without having to send a sample to a laboratory. The device makes use of the fact that light passing through liquid honey is refracted to a different degree depending on the water content: the higher the water content, the lower the refractive index. With a hand-held refractometer, this refractive index is already converted directly into a scale for the percentage water content, so that the value can be read off immediately.
For a correct measurement, the honey sample must be completely liquid and free of crystals; to achieve this, crystallized honey is carefully liquefied in a closed container in the oven at about 50 degrees and then allowed to cool again. A tiny drop is placed on the prism, the flap is closed, and the device is held up to a light source, so that a boundary line between a lighter and a darker field appears in the eyepiece, at which the scale is read.
A common mistake in practice is incorrect or missing calibration. According to the experience of the Celle Bee Institute, many privately used refractometers were not set correctly when checked, which can lead to incorrect water content values and thus, in the worst case, to violations of the legal limits or of the stricter association limits. The temperature of the sample also plays a role, since refractometers are calibrated to 20 degrees and deviations must be corrected manually if there is no temperature compensation.