At Om Metalab Services Pvt. Ltd. the dye penetration technique, a penetrating liquid is applied to the component's surface in order to penetrate the crack or discontinuity. The penetrant that flows from or is sucked back out of the crack is then seen after the excess penetrant has been removed from the surface.
Testing with liquid penetrants can be done on any non-porous, clean material, whether it be metallic or not, however it is not recommended for surfaces that are extremely rough or unclean. A dye may be present in penetrants to make the indication visible under white light, or a fluorescent substance may be present that fluoresces when exposed to the proper ultraviolet light. When maximum fault sensitivity is desired, fluorescent penetrants are typically used.
