5.1 Alkali-solubility is an indication of the degree of damage to wool resulting from certain chemical treatments, particularly when test results on the same wool, before such treatment, are available.

5.1.1 Undamaged scoured wool has typical alkali-solubility in the range of 9 to 15 %. Fine, undamaged wool normally will exhibit higher solubility than coarse wool, because of greater surface area per unit mass of fiber.

5.2 This test method is not recommended for use on wool known to have sustained alkali damage.

5.2.1 Alkali-damaged wool has had material solubilized that ordinarily would be included in the alkali-solubility test results.

5.3 Although results in one laboratory cannot usually be verified in another laboratory, this test method is considered satisfactory for acceptance testing because it has been used extensively in the trade for this purpose and because it is the only available method for assessing damage to wool by an alkali solubility procedure. Comparative tests as directed in 5.3.1 are advisable before Test Method D1283 is used for acceptance testing.

5.3.1 In case of a dispute arising from differences in reported test results when using Test Method D1283 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 which are as homogeneous as possible and which 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 result from the two laboratories should be compared using Student's t-test for unpaired data and an acceptable probability level chosen by the two parties before 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.