Assessing the Variability of Classed Fleece Lines Using a Uniformity Index

Abstract

 The International Wool Textile Organisation (IWTO) Core Test Regulations define different classes of wool lots based on wool preparation category. These definitions appear in Section 1.3 of the Regulations. Test Houses are required to identify the category on IWTO Certificates, and AWTA Ltd achieves this by attaching a suffix to the Test Number and by printing the category name on the Certificate.

These wool preparation categories are currently used in many trading contracts to specify “Classed Grower Lots Only”, or exclude particular wool types such as Bulk Classed Lots. These exclusions are an attempt by processors to reduce the variation in parameters within lots of wool included in the delivery.

Difficulties can arise for the Test House in clearly identifying any category of wool preparation based on an external examination of the bales during the sampling and weighing process. Comments have previously been made to AWTA Ltd that bales purchased as Classed Grower Lots appeared to be wool blended from various sources (Bulk Classed Lot) when opened up for processing.

The price differentials that are evident between Bulk Classed Lots and Classed Grower Lots indicate the industry’s belief that Bulk Classed Lots are inferior due to their variability and are therefore not permitted in some consignments.

The definition of Bulk Classed lots i.e. “bales containing wool blended from various sources” gives the impression of variability within the lot of wool. Conversely, Classed Grower Lots i.e. “wool from an individual grower comprising bales classed from one clip”1 would suggest a high degree of uniformity. These assumptions are generally correct however there are exceptions to the rule. Those Bulk Class operations dealing with significant volumes of wool, such as the larger Australian Brokers, have numerous bin types which help improve the matching of wool types within Bulk Classed Lots. Equally, the degree of variability in Classed Grower Lots is influenced by the uniformity of the flock of sheep and the standard of classing.

A recent trend in wool specification is to provide measurements of variation in addition to the mean for various wool parameters. Coefficient of Variation in Diameter and Coefficient of Variation in Length are two characteristics that provide useful information on the variability that is evident within wool lots. To assist the industry to evaluate the uniformity of a particular Lot, AWTA Ltd have endeavored to combine available test information into a Uniformity Index (UI).

This paper reports on the development of the Uniformity Index, and summarises the observations on the Index over the six month period from February to August, 1997.

Citation

"Assessing the Variability of Classed Fleece Lines Using a Uniformity Index", P.R. Byrne, T.J Mahar and R.W. Connors, Commercial Regulations Committee, Appendix13, IWTO Nice Meeting, December 1997