The slag lump at the forge

The big lump you see in front of you is slag. Slag is the waste material from the manufacture of iron. Have you ever seen water-filled bog holes with reddish-brown water and something resembling oil on the surface? That means the bog contains iron. The first traces of iron production in Norway are from about 300 BC. In Nore and Uvdal there are many traces of iron production, especially in Øvre Uvdal. In Smådøl there is an older ironworks, dated to 440-650 AD and one of the largest in Buskerud from this time. Enough iron for 8000 swords was produced there. Extracting iron from bog ore requires knowledge of how to find and process the ore, and skill as a blacksmith. It can take several days to chop wood and make charcoal for the process. The bog ore must be excavated, dried and burned so that all organic material is removed. Then you have pure ore for the ironworks. The earliest shaft kilns consisted of a round pipe of clay built over a large, paved pit in the ground. In this pit, both iron and slag were accumulated. In the pipe, layer upon layer of wood/charcoal and ore were laid. The slag melts first and floats to the top, while the iron becomes soft and lumpy and accumulates in the bottom of the furnace.