A method and an arrangement is provided for characterizing magnetic coating compositions that contain magnetic particles dispersed in a solvent resin matrix. The probe material is subjected to an alternating magnetic field and vertically thereto to a constant magnetic field of appropriate field strength and duration. Via a measuring coil the induced signal in the probe material is monitored and different characteristica, preferably the degree of dispersion, is measured by measuring the magnetic susceptibility of the coating material. By applying a constant magnetic field the degree of dispersion can be changed at least for a certain time. The method and arrangement of the present invention can be incorporated in an in-line system into a coating apparatus to monitor the magnetic characteristica of the coating material as well as to improve and maintain such improved characteristics.