A firmly beaten egg white is the “secret” of the success of all soufflés and many desserts; and there is no firmer egg white than the one that has been beaten by hand with a balloon whisk in an unlined copper bowl.

When egg whites are beaten in a copper bowl, the copper combines with the protein to form a polymer. Simply put, this means that the protein molecules and the copper combine to form a strong chemical chain. This allows you to beat the egg whites until they are very stiff without their breaking down.