This term is originally applied to such iron only as had been prepared solely with wood charcoal, from the ore to the malleable and finished state; but now the name of charcoal iron is given to malleable iron, the ore of which may have been smelted with coke, in the ordinary blast furnace; and it acquires its distinguishing name from the circumstance of its being refined with wood charcoal. The process of refining, and also that of puddling, are performed as one in a puddling furnace, wherein it "comes round to nature," combined with less impurities than by the common mode described. The bloom, when taken out of the furnace, is put under the heavy hammer, and brought to the form of a flat cake, when intended for sheet iron, in which state it is denominated stamped iron. The stamped iron is next broken into pieces, piled, heated, and again put under the hammer, which reduces it to a slab of about one hundred-weight. These slabs are used for a variety of purposes; but their chief application is by the manufacturers of tinned plates, who reduce the "charcoal slabs" to the required thinness preparatory to the tinning operation. (See Tinning,) When the charcoal iron is required for bars, it is treated in all respects in the same manner as in making of the very best chain-cable iron.

Owing to the large quantity and expensive nature of the fuel employed, charcoal iron is much dearer than coke iron; yet, from its great toughness and uniformity of texture, it is always preferred by engineers in the fabrication of steam-engine boilers, and, generally speaking, for all the important parts of machinery that are liable to severe tension.