5.1 Test Method D4510 for the counting of partial cleavages, may be used for the acceptance testing of commercial shipments of wool and other animal fibers, but caution is advised, since information on between-laboratory precision is limited. Comparative tests as directed in 5.1.1 may be advisable.

5.1.1 In case of a dispute arising from differences in reported test results when using this test method for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test specimens that are as homogeneous as possible and that are from a lot of material of the type in question. The test specimens should then be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using Students t-test for unpaired data and an acceptable probability level chosen by the two parties before the testing is begun. If a bias is found, either its cause must be found and corrected or the purchaser and the supplier must agree to interpret future test results in the light of the known bias.

FIG. 1 (A) Partial Cleavage-But do not count if it is at the end of a fiber. The split may have been caused by other means

5.2 Chemically damaged or tendered fibers are recognizable microscopically by qualified operators and should not be counted as partial cleavages. Such fibers exhibit total loss of cuticle, severe surface erosion, tenderizing cracks, longitudinal fibrillation, or a combination of these features (see Figs. 1 and 2). In a study of deliberately over-carbonized wool at one laboratory, it was found that when more than 24 tendered fibers were seen in 1 m, partial cleavage counts were significantly higher than on similar fibers that were not overcarbonized.

FIG. 1 (B-D) Split Fiber (continued)

FIG. 2 Fiber With Transverse Cracks