Dropping Point is also known as ASTM Method D-2265. The dropping point of a grease is the temperature at which it passes from a semi-solid to a liquid state. The dropping point test determines the cohesiveness of the oil and thickener of a grease, or when the thickener breaks down. Dropping point tests are used for quality control to verify that the soap structure has been formed correctly and will withstand high temperatures.
Does not apply for PFPE/PTFE thickened greases
The technician monitors the entire test apparatus as it is slowly heated in order to ensure that the heater block temperature and the sample temperature remain within 3°C of each other. As the temperature increases in the test apparatus, a drop of oil will fall from the cup to the bottom of the test tube at the temperature at which the thickener can no longer hold the oil. When this occurs, the technician will record both the sample and heater block temperatures on the thermometers to the nearest degree.
To calculate the dropping point of the grease, the recorded temperature of your sample is subtracted from the heater block temperature. And that value is added to the sample temperature to determine the Dropping Point.
A Dropping Point is most often performed on any soap-thickened grease. Soap thickened greases consist of simple and complex soaps. Soap-thickened greases are most often used in bearing applications in the automotive, industrial and aerospace industries.