Which of the following is NOT a main step involved in Liquid Penetrant Testing?

In Liquid Penetrant Testing (PT), the primary steps involve application of the penetrant, removal of excess penetrant, and the inspection of the test surface for indications of discontinuities. Each of these steps is crucial to the accuracy and effectiveness of the testing process.

Post-cleaning, while an important process in preparing parts before testing or after testing to remove residue, is not categorized as a main step in the actual Liquid Penetrant Testing process itself. The main steps focus specifically on the interaction of the penetrant with the surface being tested and the subsequent evaluation of any indications that may reveal defects. Post-cleaning occurs either before testing to ensure a clean surface or after testing to ensure that no penetrant residues affect further operations. Therefore, it does not fit within the core sequence of the liquid penetrant testing procedure, which is why it is the option that does not describe a main step involved in this method.