The Lost Foam Casting process originated in 1958 when H.F. Shroyer was granted a patent for this cavity-less casting method, using a polystyrene foam pattern embedded in traditional green sand. The polystyrene foam pattern left in the sand is decomposed by the molten metal. The molten metal replaces the foam pattern, precisely duplicating all of the features of the pattern. Like investment casting (Lost Wax), a pattern must be produced for every casting made.