Making and Stabilizing Foams

There are several different ways of getting bubbles into a liquid and stabilizing them. Whipping with a whisk or hand-held blender introduces air by agitating the liquid surface; the foaming wands on espresso machines shoot steam, a mixture of water vapor and air; and foaming devices for whipped cream and seltzer water mix a stream of pressurized carbon dioxide or nitrous oxide with the liquid. Any dissolved or suspended molecules in the liquid collect at the interface of the air and liquid and give the bubble wall some solid reinforcement.