The present invention uses supercritical and near supercritical fluid technology for the processing of polymer-containing formulations without induced foaming, giving benefits of either reduced melt viscosity and/or lower melt temperatures. Its application is particlarly beneficial to difficult to process materials, including unplasticised PVC, polycarbonate, PTFE, UHMWPE and polymers containing high loadings of fillers of organic origin. Shear and thermally sensitive materials can also be processed using this method with less risk of degradation, due to the lower shear input and reduced processing temperatures necessary. The production of foamed ceramic materials and metallic components by such a method is also disclosed.