Solid substances in lubricating greases lead to faults in the lubrication of rolling bearings, they influence the noise behaviour and have a wearing effect. The purity of lubricating greases is becoming increasingly important with regard to the type, hardness, quantity and particle size of the solid substances. DIN 51813 describes the quantitative determination of solids over 25 µm particle size by means of high-pressure filtration.

CleanControlling carries out the double determination by placing the lubricating grease in the clean pressing device, then the grease sample is pressed through the test sieve mesh with 25 µm mesh width. The remaining sample quantity enriched with impurities is dissolved with tepmerized solvent, filtered and the total mass of the residue of solids is determined gravimetrically.

The analysis of particle contamination in used greases provides information for conclusions on the wear behaviour of rolling bearings. In conjunction with the microscopic analysis method derived from cleanliness inspections of technical cleanliness, the results are particularly informative from particle sizes of 25 µm and above, alternatively as from 10 µm. The particle occurrence is completely measured, counted and classified according to shiny behaviour such as "metallically shiny" and "non-shiny" and documented with particle images of the largest particles. An essential step before microscopic analysis is the dissolution of the consistent greases with a suitable, tempered solvent mixture and subsequent analysis filtration.