With fluorescent dyes, ultraviolet light is used to make the bleedout fluoresce brightly, thus allowing imperfections to be seen readily. These changes, when detected, indicate the presence of change in the test object. Several techniques are used to detect and locate leaks in pressure containment parts, pressure vessels, and structures. As in ultrasonic testing, acoustic emissions can be detected by special receivers. Emission sources can be evaluated through the study of their intensity, rate and location.
Some procedures involve comparison of workmanship samples with production parts.