Foaming characteristics

The foaming characteristics rates the tendency of an oil to form or retain foam. High foam formation during the application reduces the load capacity of the lubricating film. This is particularly relevant for gear, turbine and hydraulic oils. Foaming characteristics can deteriorate due to contamination and oxidation during the oil lifetime.

Foam is formed by trapped air rising to the surface and forming foam cells. In a defined test instrument, the time it takes for the foam to decompose is monitored in accordance with ASTM D892. Thus, conclusions/estimations can be made about the behaviour in the respective application.

The foam volume is measured after the end of the air supply and after 10 minutes. The same procedure is then followed with another oil sample, first at 93.5°C and then with the same sample at 24°C.