Foam can be defined as dispersing of gas in liquid. It can be generated during production of coating (grinding, mixing and filling), during application (brushing, rolling and low pressure spraying), or when application of coat in porous substrate like wood surface. To solve this problem, the producer of coating can use defoamers as an additive. Defoamers have 3 base function, which is defoaming, deaeration and anti-foam. Defoaming performance of a defoamer is determined by how fast a defoamer can destroy foam in a liquid system. Deaeration is the process of moving the foam from the inner layer of the paint to the surface of the liquid. Anti-foam is referring to defoamers that have the ability to prevent foam formation or suppress the bubble formation, after the system has been agitated. The main rule of defoamers is more compatible defoamer with the system, will have a less defoaming effect and less hazziness. In today's market, there are 2 types of defoamers which are silicone base and non-silicone base. Silicone base defoamer can give better surface tension reduction than non-silicone base. Silicone base defoamers have a main function as deaerator while non-silicone base defoamers have main function as defoamer and anti-foam. Both silicone and non-silicone base there is for water-based system, solvent-based system, and all based system.