Volume 3, Issue 3 (May 1975)
Interlaboratory Test for Wool Fineness Using the PiMc Particle Measurement Computer System
The application of a particle measurement computer (PiMc) system for measuring average fiber diameter and variability of wool and other animal fibers has been demonstrated. Three lots of wool top and three lots of scoured wool cores representing fine (19 to 20 µm), medium (27 to 28 µm), and coarse (34 to 35 µm) grades were used. Preparation of slides of cut wool fibers and different mounting media were tested. Based on analyses from results of two laboratories, testing six lots of wool, only one had a difference in average fiber diameter between methods that was significant at the 0.05 probability level. This difference was 0.32 µm. Also, the analysis did not detect any bias or systematic error attributable to the PiMc system, nor was the difference between laboratories using different machines significant. The system reproduced its measurement results very closely. In this study, there were 24 comparisons and all differences were within theoretical differences due to chance.
The PiMc procedure of measuring fibers is over twice as fast as the microprojector and takes one less person. Alternative sampling procedures are presented showing how the sampling error can be reduced with a fixed number of fibers analysed. Based on these results, a standard computer program can be developed which generates summaries of the diameter and variability properties for wool and other animal fibers in a printout form suitable for a permanent record.