5.1 This test method is used for research, development, quality control, product specifications, and may be used for acceptance testing of commercial shipments of textile fibers. However, caution is advised since information on between-laboratory precision is lacking. Comparative tests as directed in 5.1.1 may be advisable.

5.1.1 If there are differences of practical significance between reported test results for two laboratories (or more), comparative tests should be performed to determine if there is a statistical bias between them, using competent statistical assistance. As a minimum, test samples that are as homogenous as possible, drawn from the material from which the disparate test results were obtained, and randomly assigned in equal numbers to each laboratory for testing. The test results from the two laboratories should be compared using a statistical test for upaired data, at a probability level chosen prior to the testing series. If a bias is found, either its cause must be found and corrected, or future test results for that material must be adjusted in consideration of the known bias.

5.2 This test method provides objective measurements for determining the average fiber length and length distribution in a sample of fiber.

5.3 The staple length diagram of a fiber sample can be used to determine the relative number of fibers above and below a specified length. If a fiber is too long, it will not process well in spinning, and if there is a preponderance of short fibers, the yarn might have lower than normal breaking strength.

1.1 This test method covers the determination of average staple length and staple length distribution of both manufactured and natural fibers by manually measuring single fiber lengths. This test method is also used to measure the length of fibers removed from a staple yarn, but such a measurement may not represent the fiber's staple length, as manufactured.

1.2 Because this test method requires measuring the length of only 50 fibers, it is not suitable for use in determining the number of long fibers that occur infrequently in a sample.

Note 1: For determination for overlength fibers, refer to Test Method D3513.

Note 2: For methods covering the determination of the average length and length distribution of natural fibers, refer to the following methods: for cotton, Test Method D1440, and Test Method D1447, for wool, Test Method D519, Test Method D1234, and Test Method D1575.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.