Micron (wool)

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A micron (micrometre) is the measurement used in wool classing to measure the actual diameter of a wool fibre. The smaller the number the finer the fibre.

Every fleece comprises a very wide range of fibre diameters - for example a typical merino fleece will contain fibres of as low as 10 microns in diameter, and there could be fibres with diameters exceeding 30 microns, depending on the quality of the fleece. What is usually referred to as wool's "micron" is the mean of the fibre diameters or average diameter. This may be measured in a number of different ways.

On the animal or the fleece in the shearing shed, small samples can be taken and measured using a portable instrument such as an OFDA2000 (Optical Fibre Diameter Analyser); or a mobile instrument system called a Fleecescan. Both these systems have been studied extensively and used correctly should give reliable results. Samples of fleece can also be sheared from the animal and sent to a laboratory for measurement ("midside sampling"). Most fleece-testing laboratories nowadays use related instruments to those metioned - either the OFDA models or the Laserscan.

Once the fleeces are baled and prepared for sale as lots, they are commonly sampled by coring in the broker store and the samples sent to certification laboratories. Here the core samples are cleaned and prepared for measurement under strict test methods. Merino wools are normally measured on Laserscan instruments in Australia, New Zealand and South Africa, although OFDA instruments may also be used in some cases (the results from these two types of instrument are quite similar). Crossbred and coarse wools are often measured for mean fibre diameter by older instruments - "airflow" in many parts of the world, and even projection microscope in some cases (although this method is not very precise on raw wool).