What’s lost foam casting? Lost-foam casting (LFC) is a type of evaporative-pattern casting process that is similar to investment casting with foam as the pattern. In most cases the pattern is molded in polystyrene (2.5% polystyrene and 97.5% air) in a closed mold. The molten metal is poured on to the top of the gating system, which is responsible for directing the molten metal through the cluster. The molten metal being poured causes the pattern made in the first step to immediately vaporize.