Introduction to Liquid Penetrant Testing Liquid penetrant inspection is one of the oldest and most widely used non destructive testing methods. It is also called as dye penetrant inspection. Penetrant testing can be applied to most of materials including metallic and non metallic objectsMetallic materials include aluminum, magnesium, titanium, castiron,stainless steel, powdered metal products, copper, brass, bronze,etc. Nonmetallic materials include ceramics, plastic, moldedrubber, composites, glass, etc. Penetrant testing can’t be applied on a porous surface Penetrant Testing History Penetrant first used in 1900 s to detect cracks in locomotive parts The method was called oil and whiting The method used dirty lubricating oil that was thinned with kerosene followed by application of chalk coating which absorbed oil from the cracks In 1940 s fluorescent or visible dye was added to the o...