Opportunities for the simultaneous estimation of essential fleece parameters in raw cashmere fleeces

Two models for the simultaneous estimation of fibre quality and yield in non-separated raw cashmere fleeces based on the Wildman/Bray-formula and the application of the optical fibre diameter analyser (OFDA) are described. The first model is based on length-biased cashmere subsamples; thus, this model requires the application of a minicore sampler. If there is no minicorer available, the second model can be used which is associated with higher measuring and calculating efforts (measurement of down fibre and guard hair length). To check the applicability of these models, 18 raw cashmere fleece samples (first model) and 30 simulated cashmere fleece samples with defined fibre length (second model) were evaluated for mean fibre diameter and cashmere weight. The samples were analysed by means of the OFDA; the resulting fibre diameter distributions given in a histogram were separated into a down fibre and a guard hair distribution. Additionally, the effect of different separation criteria for distinguishing between down and guard hairs, one fixed (down fibres 4-30 μm) and two 'more objective' criteria (fitting of a Gaussian normal and a lognormal distribution to the down fibre peak), on the yield and quality evaluation was investigated. It is shown that the most accurate evaluation of the cashmere quality can be realised whilst using the first (r = 0.930) and second separation criteria (r = 0.932). Strong and highly significant correlations between the actual cashmere yield and the OFDA-estimated yield values were obtained for the three separation criteria in the first model (r = 0.970, 0.970 and 0.968). There were no significant differences between the three separation criteria. Thus, it is not necessary to use one of the 'more objective' criteria for the cashmere yield and quality evaluation, which requires a higher calculating effort than the first criterion. To reduce the calculating efforts in a further step, the mean specific gravity of the guard hairs can be used for the yield evaluation instead of the fleece-specific guard hair density. The second model yields also a respectable result, however, the simulated fleece samples did not require the calculation of fibre length. A high and significant correlation coefficient of r = 0.952 was calculated between the actual and OFDA-based cashmere yield. © 1997 Elsevier Science B.V.