The antifoaming or antifoaming ability of organosilicon is due to its low surface tension. Silicone compound (silicone oil) interferes with the surface tension of gas-liquid interface, resulting in defoaming effect. When silicone is added to the foam medium, the small particles of silicone oil fall onto the surface of the bubble, while effectively reducing the surface tension of the contact point, causing a thin weakness in the outer skin, resulting in bubble breaking. The best antifoaming activity standard can be described as follows: the free small particles of silicone oil must be completely, as quickly and effectively dispersed into the active area as possible. The silicone oil is very small and has a very large proportion of SiO2 filler. It is dispersed rapidly and causes demulsification and bursting outside the contact point of SiO2 particles. Due to the burst of foam near the foam, the foam is unstable, accelerating the continuous bubble breaking effect, and finally reaching a stable state. If it is emulsion defoamer, the emulsion is too stable, which will reduce the defoaming effect. When the stability is poor, it has great activity. Therefore, it is necessary to balance the stability and activity, and choose organosilicon compounds with low solubility and high activity in water and oil phase. The functions of defoamers are also defined according to three mechanisms: bubble breaking, defoaming and bubble inhibiting. Bubble breaking: when it enters the bubble from the air side relative to the foam, it will burst together. Bubble suppression: enter the bubble from the liquid side and destroy the bubble unity. Defoaming: from the bubble interface into the bubble, so that the bubble together float out of the liquid surface.           
Defoamer includes oil type, solution type, emulsion type, solid powder type and compound type.