Iron-arsenic alloys are described in many medieval chemical recipes as a means to liquefy iron. In fact, while such alloys have relatively low melting points, they are not the only examples of iron being known as a liquid metal. There is evidence from the analysis of swords, as well as from written references, that crucible steel, probably imported from the Middle East, was known in Western Europe from the Early Middle Ages. In addition, the blast furnace, which produced liquid pig iron, is now known from archaeological evidence to have been operated from at least the thirteenth century in Scandinavia. The descriptions of iron-smelting and iron-working given in the accounts written by scholastic alchemists are in fact closely related to the contemporary practices of craftsmen operating iron furnaces.