Malleable iron castings are produced by heating castings made of white or mottled charcoal iron, smelted from hematite ores. The patterns should be made with a double allowance for contraction, and in the foundry the " gates " should be wide and thin. The thickness of the metal should be uniform, and no greater than is necessary. When ready for annealing, the castings should be brushed and packed in iron boxes, each casting being surrounded by a mixture of fresh hematite (red iron ore), hematite already used in the annealing process, and iron scale from the rolling-mills. The box is covered up, placed in an annealing oven, and fired at a bright red heat for from three to seven days. After withdrawing from the furnace, the boxes are allowed to cool, and the castings are cleansed from the adhering ore. The castings will now be tough, strong, flexible, and much softer, and may be forged. If the process has not been carried far enough, there will remain a core of unconverted iron. Cast-iron contains a high percentage of carbon, whilst the converting material is rich in oxygen. It is generally considered that the change which takes place is due to the oxidation of the carbon contained in the iron.

Bends, tees, crosses, etc., for steam-pipe connections, also small brackets for brake levers on omnibuses, are often made of malleable cast-iron for the sake of lightness and strength. Sometimes flexibility is sought, as in ornamental castings for umbrella stands, etc., which may be cast flat, leaves, tendrils, etc., being afterwards bent and twisted to the desired shape.