An anti-foam additive is used in manufacturer to prevent the formation of foam, or it is added to a mixture to destabilize foam and act as a bubble breaker, breaking the foam that has already formed. The terms defoamer and antifoaming agents are often used interchangeably. In fact, they are not quite the same. A defoamer is a surface active agent that stops the foam and breaks the bubble once it has been formed. It is a bubble breaker. An antifoaming agent prevents the formation of foam so it never forms. The term foam-control agent is a more appropriate term to use and they function by a variety of mechanisms to prevent or rupture foam.