A Defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids.

The additive is used to prevent formation of foam or is added to break a foam already formed.

Generally, a Defoamer is insoluble in the foaming medium and has surface active properties. An essential feature of a Defoamer product is a low viscosity and a facility to spread rapidly on foamy surfaces.

It has affinity to the air-liquid surface where it destabilizes the foam lamellas. This causes rupture of the air bubbles and breakdown of surface foam.

Entrained air bubbles are agglomerated, and the larger bubbles rise to the surface of the bulk liquid more quickly.