The water washing residue detector dries and weighs the non dispersible substance, and the amount of residue is expressed as m/kg (ppm) of the original sample. This method provides fast results that can be compared to the limit values specified in quality control. In some cases, impurities need to be classified under an optical microscope based on their color, form, and surface quality. Magnetic components can be detected using strip magnets. If these methods do not meet the requirements, X-ray microanalysis (XMA) or energy dispersive X-ray microanalysis (EDX) can be used to determine the composition of elements in individual particles on the surface, and to find the source of non dispersed substances in this way.