Fibre Diameter Measurement
Fibre Diameter of wool can be measured using a number of different technologies.
AWTA Ltd uses the LASERSCAN for all fibre diameter certification and fleece measurement services.
STEPS IN DETERMINING FIBRE DIAMETER
During the residual sub-sampling process for yield determination, 20g of scoured wool is removed for fibre diameter measurement.
1. Analysing
The scoured sub-sample is carded using a Shirley Analyser. This removes vegetable matter and blends the fibres in an open web.
2. Conditioning
The Shirley Analysed web is left in a controlled atmosphere room to condition to an environment of 20°C and 65% RH. Because wool swells as it absorbs moisture, the fibre diameter is dependent on atmospheric moisture content. Hence, for consistent measurement for certification purposes, the fibres must adjust to these standard conditions before measurement and certification.
3. Measurement
Mean Fibre Diameter is measured by Laserscan. Results are reported as micrometers (microns).
The conditioned web is split into 4 portions, each to be measured in at least 2 Laserscans. The web is placed into a mini-core set above the Laserscan.
The cored snippets fall into the Laserscan and are automatically mixed into a solution within the instrument.
The slurry of fibre snippets moves through tubing into a measurement cell where a laser beam shines on the individual fibres. The shadow cast by the fibre is measured electronically and stored in a “bin” representing the micron grouping measured by the instrument. After measurement, the fibres are caught in a cloth filter for subsequent removal. Each snippet is only measured once.
Each Laserscan is calibrated to an international series of wool tops that have been measured by the 100 or so laboratory members of Interwoollabs. Consequently, the “bin” to which an unknown fibre is allocated can be directly related to a micron value.
For each portion of the web 1000 fibres are measured. Hence, 4000 fibres are measured for the certified Mean Fibre Diameter result. Because the measurements are made on individual fibres, a distribution of the diameters in the sample can be accumulated and graphed as a Histogram. Also the Coefficient of Variation of Fibre Diameter can be calculated. In addition, for appraisal purposes, the Certificate can show the Mean Curvature of the fibres in the sample and the Comfort Factor of the sample.