Surface Viscosity and Gushing

Surface viscosity correlates qualitatively with gushing induced by a standard gushing test. Substances which provoke gushing cause a large increase in surface viscosity when they are added to beer. Conversely, the very high surface viscosities induced by gushing agents fall to normal or intermediate values when anti-gushing agents are added. High surface viscosity does not ‘cause’ gushing, but appears to be a frequent concomitant of the existence of stable nuclei. These observations support a hypothetical mechanism which suggests that anti-gushing agents should be extremely surface-active but incapable of forming a solid-condensed surface film.