This invention provides packages and containers produced by a solid state method for the manufacture of foamed polymeric material. The packages are suitable for pre-cooking or sterilization, insulated transport, cooking vessel, reheating, and storage of food. The gas impregnated thermoforming (GIT) process includes interleaving an article of raw polymeric material with a gas channeling means; exposing the article to a non-reacting gas at elevated pressure to achieve a desired concentration of gas within the polymer, thereby forming a partially gas-saturated article, separating it from the gas channeling means, then decompressing, foaming and forming it at a temperature below the material's melt temperature; and finally trimming it to produce a finished foamed polymeric material and recycleable scrap solid state process foamed polymer.