Foam is a dispersion of air and other gases in a liquid or solid. Apart from a few exceptions (foams in shampoos, shaving creams, hair styling mousses, carpet cleaners, polyurethane or other polymers that insulate homes) foams are generally undesirable. Foams disturb production sequences in which liquids, particularly water, have an important function as transporting media, and in the worst cases they can even bring such processes to a standstill. Furthermore, foams can lead to lower production yields and finished products of poorer quality.