This specification establishes the classification, technical requirements, tests, and test procedures for the qualification, approval, and quality verification of all materials used in the liquid penetrant methods of inspection with the exception of those excluded in the application section. AMS2644J addresses methods that were recently developed for evaluating Method B and D penetrant water solubility and adds reference to Method A(W) throughout. The revision updates references (see Section 2), clarifies definitions (see 2.6.3), adds the water solubility test (see 3.3.8.6), clarifies water content testing (see 3.3.8.8), clarifies scope of concentration requirements (see 3.3.9.5), updates the requirements for acceptance testing (see 4.2.2.1), adds alternative material for testing (see 4.4.2 and 4.4.5.2.1), removes data validity evaluation (see 4.4.5.1.6), increases temperature range for testing (see 4.4.5.2.1), clarifies developer testing (see 4.4.12.1), adds language to address global shipping (see 5.3), updates Table 3 in line with text (Method C, Removers and Developers), revises Method C, Removers, removes specific Developer tests in Table 4, and adds Method A(W) to Tables 5 and 6.