Dark Fibre Contamination in Wool - Its Prediction and Ramifications

This paper has been reproduced from the original source document using Optical Character Recognition software to convert printed text into electronic format. The source documents are no longer in print. The papers cover work into dark fibre measurement and risk assessment conducted by CSIRO's Textile and Fibre Technology Division , when it was located at Ryde, NSW. It has been necessary to reformat the document and hence the page numbering and layout is no longer identical to the original, but the text is identical, except where obvious errors have been corrected. 

Abstract

Topmakers have set maximum limits for dark fibre contamination which are very low, typically one hundred dark fibres per kilogram of top. This can originate from less than five grams of dark fibres per bale of wool, which is a level of contamination much too low to permit any realistic sampling and testing to be carried out. For example, just to find out if there is any dark fibre present would require sampling more than a hundred kilos of greasy wool from each sale lot. Therfore a presale test is not realistic

An alternative approach must be considered, and this is the basic reason behind the search for an objective risk level rather than an objective test on the greasy wool.

It is proposed that the risk of dark fibre contamination be quantified in terms of eight risk levels. Risk levels one and two should be satisfactory for the white and pastel trade. Level eight is the highest risk category. The risk levels are derived from consideration of various factors of breeding, husbandry and wool harvesting.

A concept of a dark fibre "Decision Tree" for the assessment of the risk level  is discussed. An outline of the decision tree is presented.

The decision tree works  as follows:

• At every branch point a question is asked which has one of two answers, indicating one of two branches. -This leads to the next branch point.
• After the question has been answered at the final branch point, the final branch leads to a definite risk level.
• The questions at each branch point have been chosen so that they can all be answered objectively from information on various factors of breeding, husbandry and
  wool harvesting.
• All of this information could be obtained at shearing time.

Citation

"Dark Fibre Contamination in Wool - Its Prediction and Ramifications", Foulds R.A., Seminar Proceedings: Technical Feasibility of Sale by Description, CSIRO Division of Textile Physics, July 1988