foam containing the hardener agent the flow of the resin milk or resin solution forms a flowing layer or flowing curtain respectively which features the shape of the cone shaped shell and which extends from the end of the pipe outwards to the wall of the mixing chamber or the discharge pipe respectively upon impingement of the thin flowing curtain on the wall the flowing mass is reflected and provides therewith the necessary vacuum or subpressure because the entire flow is directed forwards and achieves therewith a good mixing and acceleration of the foam the tenside foam produced by the agency of pressurized air flows in the outer pipe with an extremely low speed or velocity of flow towards the resin curtain and is aspirated into said resin milk due to said vacuum at said resin curtain whereby thereupon the excellent state of mixture the additional superfluous air originating from the addition of the foam and the vacuum of the flow produces the after foaming of the mixture necessary for the production of the foamed material or article preferably aqueous solutions of condensation products of urea and formalin are utilized for producing the resin milk or resin solution respectively the water contained in the resin milk is thereby utilized also for aiding in the production and forming of the foam cells during the after foaming the weight of the freshly produced foam.