Some people studied the defoaming process of polysiloxane in the oil system. They continuously photographed the foam system at 1/1000 seconds and magnified the image 100 times. The 4 pictures showed that silicone oil defoamer droplets reached the bubble film, and the surface of the bubble was broken and merged into bullae. From 1~3, the foam was consolidated from 4 to 1, and the film became thinner. At last, the gas and liquid separated rapidly, and the big bubble was eliminated. At the end of 4, the bubble was broken. This also objectively explains why a drop of defoamer goes down and a series of bubbles burst.            When defoamer is attached to the foam film and immersed in the foam solution, the surface tension will be significantly reduced. Because in water system, the solubility of the active components of defoamer to water is small, the reduction of surface tension is only limited to the local part of the bubble membrane, while the surface tension around the bubble membrane has almost no change. The part of the surface tension that is reduced is strongly drawn and stretched around, resulting in foam rupture.