Magnetic particle testing is a proven method for fast and reliable crack and defect detection on ferromagnetic materials such as steel or cast iron. The component is magnetized so that a magnetic stray field is created at defects such as surface or near-surface cracks. The finest magnetic particles accumulate precisely at these points and make the defect visible as a clear, easy-to-interpret display – in daylight or under UV light, depending on the system. In this way, even very small, safety-relevant irregularities can be efficiently detected and quality in production and maintenance can be sustainably assured.