Speaker Notes

Written by: Dr. Trevor Mahar, Australian Wool Testing Authority Ltd.

The development of objective measurements for greasy wool has enabled the prediction of top characteristics to be placed on an objective basis for the first time. Prior to this, evaluation of processing performance was a matter of experience and judgement.

One of the most important customer requirements that a topmaker is trying to meet is Hauteur, or average fibre length. The topmaker also has to fulfil specifications for the distribution of fibre length, coefficient of variation of Hauteur (CVH), and also the short fibre content of the top. Each of these characteristics is considered important by the spinner. The length properties are second in importance to diameter in determining the value of a top.

Top fibre length properties depend on:

• the original fibre length of the greasy wool;

• the amount of fibre breakage (dependent on, e.g. fibre length, fibre strength, fibre entanglement and fibre crimp);

• the location of fibre breakage along the length of the fibre

Due to the nature and complexity of raw wool consignments compiled to produce tops, it is a difficult matter to measure average FIBRE properties. In an ideal world this would be done.

However in each case listed there is a a measure which can be used to ESTIMATE the fibre properties listed.
Wool Staple Length can be used to estimate fibre length. The amount by which the average fibre length is greater than staple length is termed the fibre length to staple length ratio. This ratio commonly varies from 1.0 to 1.35 with an average of 1.17.

Similarly Staple Strength and Position of Break (POB) in a staple can be used to estimate fibre strength and fibre "point of break".