English: A technician performs magnetic-particle inspection (MPI) on a pipeline to check for stress corrosion cracking. The technique used here involves black particles in a wet suspension sprayed onto a surface prepared with white contrast paint, a technique known in the trade as "black and white" MPI. In the left picture the technician is holding a magnetic yoke (horseshoe-type electromagnet) against the pipe while spraying the liquid onto the magnetized area between the poles. In the right picture the technician watches the liquid flow while checking for indications of cracking, which would appear as small black lines. No indications of cracking appear in this picture; the only marks are the 'footprints' of the magnetic yoke and drip marks. In these pictures, the pipe is sitting on a steel support in a shop after being removed from service for testing.