A black light is used with the fluorescent liquid penetrant examination method.

A black light is used with the fluorescent liquid penetrant examination method.

• A. False
• B. Not required
• C. True
• D. Optional

Answer: (C)

Fluorescent liquid penetrant inspection relies on a penetrant that contains fluorescent dye, which glows when excited by ultraviolet light. A black light provides the necessary UV illumination to make the dye fluoresce, revealing surface defects as bright indications against a dark background. In practice, you inspect in a dim or dark area with a UV-A lamp to clearly see those fluorescence indications after the penetrant, remover, and developer steps. Because the method depends on fluorescence under UV light, using a UV or black light is essential, not optional or unnecessary.

Fluorescent liquid penetrant inspection relies on a penetrant that contains fluorescent dye, which glows when excited by ultraviolet light. A black light provides the necessary UV illumination to make the dye fluoresce, revealing surface defects as bright indications against a dark background. In practice, you inspect in a dim or dark area with a UV-A lamp to clearly see those fluorescence indications after the penetrant, remover, and developer steps. Because the method depends on fluorescence under UV light, using a UV or black light is essential, not optional or unnecessary.