Magnetic particle testing (also known as flux testing, MP testing, or MT testing) is a method of non-destructive material testing. It is suitable for detecting predominantly gap-like material separations (e.g. cracks) in the surface and in the near-surface area. Ferromagnetic materials can be tested. To apply the magnetic particle method, the workpiece must be magnetized in the test section. An optimal fault display is obtained when the magnetic field penetrates the material defect perpendicularly.