What is required to activate fluorescent penetrants during inspection?

Fluorescent penetrants require ultraviolet (UV) light to be activated during inspection. This specialized lighting causes the penetrant that has been absorbed into a defect to fluoresce, making it visible against the background surface. The UV light excites the dye in the penetrant, which emits a bright, vivid glow that aids inspectors in identifying flaws such as cracks, porosity, or other discontinuities in materials.

The effectiveness of fluorescent penetrant testing hinges on proper lighting conditions, whereby using UV light intensifies the visibility of penetrant indications as opposed to visible or infrared light, which do not have the same activating properties.