BLISTER STEEL, a special variety of steel made by the cementation process, in which, under great heat, iron is changed into steel by the penetration of carbon into its substance. Bars of wrought iron are brought into contact with charcoal in a closed furnace for a week or ten days and heated to about i .000° C. In these conditions the carbon dissolves in the metal and pene trates it, changing the iron into steel. The name "blister steel" arises from the fact that as the carbon, diffusing in the iron, meets the particles of slag which are always present in wrought iron it forms carbonic oxide, which, unable to escape, puffs up the molten metal and causes blisters. Blister steel is not a homogeneous product. Its special employment is in making crucible cast steel.
(See IRON AND STEEL.)