Anti-Foaming agents are sometimes added by brewers to either boiling wort or fermenting beer to reduce the size of the foam cap on top of the wort. This antifoaming agent takes the form of a liquid silicone material that works by reducing the surface tension of the wort. The reduction of surface tension also prevents the release of foam-positive wort components, enhancing foam formation in finished beer. In the kettle, anti-foaming agents help prevent dangerous boilovers. Used in the fermenter, reduction of the foam cap provides the advantage of increasing the working capacity of the vessel. Typical fermentation vessels require up to 30% headspace above the liquid level, especially when vigorous ale fermentations are employed. Other benefits may include better hop utilization because of reduced bitterness loss associated with normal foaming and easier cleaning of vessels. Silicone-based antifoaming agents are removed during filtration and/or centrifugation and should not survive into the finished beer.

See also foam.