Dye Penetration (liquid)

    Liquid Penetrant testing is probably the most widely used NDT method. The test object or material is first thoroughly cleaned and then coated with a visible or fluorescent dye solution.

     After a pre-selected time interval (dwell time), the excess dye is removed from the surface, and then a developer is applied. The developer acts like a blotter and draws penetrant out of imperfections which are open to the surface.

    With visible dyes, the vivid color contrast between the penetrant and the developer makes the "bleed-out" easy to see.

     With fluorescent dyes, an ultraviolet lamp is used to make the "bleed-out" fluoresce brightly, thus allowing the imperfection to be seen readily.