Refractometer
Lexikon
A refractometer is an optical measuring instrument 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 instrument with which beekeepers can determine the water content of their honey themselves, without having to send a sample to a laboratory. The instrument makes use of the fact that light is refracted to different degrees when passing through liquid honey depending on the water content: the higher the water content, the smaller the refractive index. In a hand-held refractometer this refractive index is already converted directly into a scale for the percentage water content, so the value can be read off immediately.
For a correct measurement the honey sample must be completely liquid and free of crystals; crystallized honey is therefore carefully liquefied in a sealed container in the oven at about 50 degrees and then cooled again. A tiny drop is placed on the prism, the flap is closed and the instrument is held up against 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 Bee Institute Celle, a check found that many privately used refractometers were not correctly set, which can lead to incorrect water content readings and, in the worst case, to violations of the statutory limits or 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 without temperature compensation.