Liquid penetrant inspection (LPI) is used to ensure that each casting produced is free from manufacturing defects that might be too small to see with normal visual inspection. The castings are dipped in penetrant with a very high capillary action and allowed to set long enough for the penetrant to be pulled into any defects connected to the surface. After the set time is completed, the penetrant is rinsed off the surface with water, and the part is dried. Once the dry time is complete, the casting is viewed under a UV black light. Any of the high capillary action penetrant that was drawn into surface defects is not rinsed off by the water and glows bright green under the black light to allow defects to be plainly identified.