Compression set is just one of the many factors screen printers must consider when choosing the correct durometer squeegee for their printing job.
It describes the blade’s ability to return to its original shape. As the blade is used at an angle and under pressure, it bends opposite the direction of the print. As the blade conforms to this shape, the pressure on the mesh is reduced, the deposit varies, and the speed must be reduced. Compression set is more prevalent with higher durometer blades and is accelerated with excess angle and pressure.
Source: Joe Clarke