ABSTRACT
In principle, bubble-point measurement is simple. Place a 47-mm-diameter disk of a filter medium into a suitable housing. Flood it with water, making sure all pores are filled, leaving a layer of water on top. From underneath apply a slowly increasing pressure of air. Look for the first perceptible bubble coming out of the water layer. When the bubble appears, note the pressure underneath. That is the bubble point. Deduce the diameter of the largest pores from that pressure and the surface tension of the wetting liquid, as explained in Figure 4.1. In this test, much of the water in the medium is pushed to the top as the largest pores on the surface blow open. More pressure is required to blow open the smaller pores.
