Abstract: A method for the production of integral skin foam is provided. An inert, non-flammable gas is added together with a low quantity of hydrocarbon fluid to a liquid skeleton substance. Only the inert, non-flammable gas serves during energy supply for foaming up the skeleton substance. The hydrocarbon fluid promotes the formation of a dense outer skin of the integral skin foam. The liquid skeleton substance is brought into a chamber and a sonochemical process is brought about in order to dissolve the gases in the liquid skeleton substance. The hydrocarbon fluid is less than 1% by volume of the inert gas and the liquid skeleton substance.