ABSTRACT
Water is a wonderful, non-toxic, non-flammable ‘solvent’ or process liquid. One of its drawbacks however, is the very high surface tension of 72 dyn cm-1. Low-viscosity liquids generally have a fast flow and fast drainage, and higher viscosity liquids have a slower flow. This surface flow is also influenced by the presence of surfactants. If a double layer is deformed by any kind of stress which causes a reduction in the density of surfactant molecules, this area has a higher surface tension. The system tries to compensate by migration of surfactant molecules from the bulk liquid into the stressed area and shift of molecules from the double layer into the region. Foam can basically be destroyed either by mechanical action or by the addition of special agents. These agents are called by various names such as antifoams, defoamers, deaerators, foam control agents, and antifoaming agents, depending also on the time or status when the defoamer is active.
