This inspection method works by applying a liquid dye penetrant to the surface of a component. Any defects on the surface draw the penetrant in using capillary action. After a set amount of time has passed, any excess dye is removed and a developer applied to the surface. A visual inspection is then performed to identify any flaws or defects in the component.

Dye Penetrant Inspection is a non-destructive testing technique commonly used to detect defects in castings, forgings and welding.