Dye penetrant inspection

A method of nondestructive inspection used to detect surface defects in metal or plastic parts. The part to be inspected is soaked in a penetrating liquid for a specified period of time, and then all the penetrant is washed from its surface. The surface is then covered with a developing powder that pulls the penetrant from any defects that extend to the surface of the part. The penetrant plainly shows up on the powder-covered surface, outlining the defect.