Liquid penetrant testing is a non-destructive surface inspection method that uses highly permeable liquid to penetrate into the surface defect of the component, and then try to make it show the defect. According to the different penetrants used, it can be divided into colored penetrating method and fluorescent penetrating method. STEMart provides liquid penetrant testing for surface quality detection of non-porous materials (such as metal, plastic, glass, ceramic and steel parts). https://www.ste-mart.com/liquid-penetrant-testing.htm