Liquid Penetrant Testing (LPT), also known as Liquid Penetrant Inspection (LPI) or Dye Penetrant Testing (DPT), is a widely used non-destructive testing (NDT) method to detect surface defects and discontinuities in materials. It is particularly effective for inspecting non-porous materials like metals, ceramics, plastics, and some non-metallic materials.

Dye penetrant testing (PT) is a non-destructive material testing method which uses capillary forces to find surface cracks or pores and make them visible. It can detect surface-breaking flaws such as cracks, laps, porosity.