The method shows how much foam is formed when air bubbles rise to the surface in oil at rest and the duration of the foam. From this, the behaviour during use can be estimated. Oils which produce a lot of foam or very persistent foam are not suitable for some applications.
Brief description of the method
The test oil is placed in a graduated cylinder and maintained at 25°C . Then, air is passed through a diffusor stone into the oil. The air bubbles rise to the surface and form a foam layer. After a period of 5 min, the air flow is shut off and the volume of foam is measured immediately. After ten minutes, the remaining volume of foam is measured again. The test is repeated with a second sample at 95°C and 25°C.