Review of the Subsample Mass Limit for Yield Testing of Scoured Wool

Abstract

In December 1995, a paper was presented to IWTO which evaluated a prototype blender for core samples of scoured and carbonised wool. The blender was designed to minimise static electricity thus allowing scoured or carbonised wool to be blended when Wool Base or other parameters were to be measured. The results of the evaluation demonstrated that the prototype blender provided a satisfactory way of blending core
samples of scoured or carbonised wool.

In a supporting paper to the above, amendments were proposed to IWTO-33-88(E) that stated, “the whole of the representative global sample drawn from the lot (ie. not less than 500g) must be used to determine Oven-Dry mass unless the global sample is blended.” The paper made a further recommendation stating that, “After blending, reweigh the sample to 0.1g and use the mass (Wb) for determining the factor Wb / W. Immediately after reweighing, draw at least 3 subsamples of not less than 100g and weigh each to 0.1g.”

Since the introduction of the scoured wool blender into each of the three AWTA Ltd laboratories, difficulties, due to the bulk of the subsample, have been experienced by laboratory operators in trying to place a 100g subsample of scoured wool into a drying can. A potential solution to the problem is to reduce the minimum subsample weight required for determining Oven-Dry mass and additional information such as Wool Base, Vegetable Matter Base, Ash Content, and Residual Fatty Matter. This paper reports on a trial aimed to assess the effect on these components using a minimum subsample mass of 80 grams compared to the 100 grams required in IWTO-33-88(E).

The results indicate no significant effects on either the result that would be certified or the testing precision and it is therefore recommended that IWTO-33-88(E) be amended to allow for a minimum subsample mass of 80 grams

Citation

"Review of the Subsample Mass Limit for Yield Testing of Scoured Wool", P.R. Byrne, Report 01, Raw Wool Group, IWTO Nice Meeting, November 1998.