Which of the following is NOT considered a basic inspection principle in penetrant methods?

The statement that indications glow when illuminated with a black light is not a basic inspection principle in the liquid penetrant testing method. While it is true that many penetrant materials are fluorescent and will exhibit a glow under UV light, the fundamental principles of penetrant testing focus more on the preparation and application processes rather than the specific visual characteristics of the indications.

In penetrant testing, the basic principles include ensuring that all surfaces are clean prior to testing to achieve accurate results, allowing sufficient dwell time for the penetrant to seep into any surface defects, and utilizing developers that enhance the visibility of the indications for better detection. These principles are critical for maximizing the effectiveness of the test and ensuring that any potential defects are accurately identified.