Explaining foam in the absence of soap: It’s a tension gradient

Enlarge (credit: Puamelia/ Flickr)

Foaming is nature's way of making beer even more delicious. Yet not all foams are understood because they don't seem to obey the model that explains most of the rest. Understanding these atypical foams is important, because they often apply in the food-processing and petrochemical industries. So having a new paper that tells us what allows these foams to survive may be of more than academic interest.

Foaming with cause

Foams and froths form when two different liquids are mixed with a gas such as air. But not all liquid combinations will allow a foam to form, no matter how hard you beat it-I'm looking at you, experimental dark chocolate meringues. While a foam is actually a rather complex beast, the basic physics is not too difficult.

A foam is basically a set of air bubbles, enclosed by thin films that form a self-supporting network. The thin films are subject to two competing forces. The liquid trapped in the interface slowly drains away due to gravity. This causes the layer enclosing the air to thin, which will lead to the eventual collapse of the foam. But the loss of fluid is often slowed (or even entirely prevented) by two factors.

Read 9 remaining paragraphs | Comments