Duramold is a composite material process developed by Virginius E. Clark. Birch or poplar plies are impregnated with phenolic resin and laminated together in a mold under heat and pressure for use as a lightweight structural material. Similar to plywood, Duramold and other lightweight composite materials like the similar Haskelite were considered critical during periods of material shortage in World War II, replacing scarce materials such as aluminum alloys and steel.