An article of manufacture is made by filling a container with expanded thermoplastic elements that are in a non-cured state and that possess a degree of latent foaming ability. After filling the container with the non-cured elements, the elements are allowed to cure under ambient conditions during which the blowing agent remaining in the elements in a vapor state condenses allowing air to be drawn in while the elements expand. This expansion of the elements distends and rigidifies the container where the container is allowed to expand or places an item packaged within a container of rigid construction under a tight fit.