loup

A loup is a pasty, partially refined mass of iron that emerges from the bloomery or early smelting stage, before it becomes workable wrought iron. It sits in the middle ground between raw ore and finished metal: still full of slag and impurities, but concentrated enough to be shaped by repeated hammer blows or passage through rolls. The name comes from Old Norse and Old English roots meaning a lump or mass, which is precisely what it is.

In traditional bloomery ironmaking, the loup formed naturally inside the furnace as carbon and impurities were consumed or separated. Once the bloom was extracted and cooled enough to handle, smiths would pass it repeatedly under a trip hammer (a heavy head lifted by a rotating shaft, then allowed to fall) to squeeze out embedded slag and compress the iron. Each strike forced more slag to the surface where it could be brushed away, gradually improving the metal's quality and density.

The loup's condition was critical. If it remained too cold and brittle, hammering would crack rather than consolidate it; too hot and it would fall apart. Experienced workers judged readiness by color and behaviour under the hammer. A well-prepared loup could then be reheated, folded, and shaped into bar iron or billets for further refining, or sent directly to a smith for forging into tools and weapons.

The term became less common as technology shifted. Finery forges and later puddling furnaces produced iron that bypassed the loup stage or refined it more efficiently in the furnace itself. By the 19th century, industrial rolling mills and blast furnaces had displaced the bloomery and trip-hammer workflow almost entirely in Europe and North America, making the word obsolete in active metalworking but persistent in historical and archaeological literature.