On the 18th of August there was a yearly festival in Reykjavik commonly known as cultural night. The excavation participated with hourly guided tours of the site and old style blacksmiths were on the site working their trade. In the spirit of this event I want to write about the ironworking area that was found at Alþingisreitur during the excavations in 2008-2009.
This was a well preserved iron working site with a charcoal pit, furnaces, anvil stone, a drain and quite a lot of slag. The charcoal pit was discovered in the North corner of the excavation, which is where the charcoal for the iron production must have been made out of the surrounding birch forests.
Three furnaces in a row from the site can be seen on the image above. These were used to work iron out of bog iron. Close to this working area there was a mire from which this bog iron must have been taken. Although they appear to be just a hole in the ground the furnaces were built up around those holes and mainly made of turf. But when they are found in excavations they have been destroyed and the turf has usually fallen into the holes.
Here is a closer look into one of these furnaces, which is black and orange inside due to the burning charcoal and iron ore.
The furnaces were similar to this one when they were in use.
The process of getting the iron out of the bog iron or iron ore was as follows:
The bog iron/iron ore and charcoal was layered on top of each other into a few layers in the bottom of the furnace. Then the charcoal was lighted and the flame exited with bellows as the man in the illustration above is doing. This way the bog iron heated up and the slag was melted out of it and into the bottom as it has a lower melting point than the iron. When the slag had melted out of the iron the iron would then end up in a spongy iron material called bloom which collects on top of the slag.
This slag chunk that was found during the excavations this summer is most likely from the bottom of one of these furnaces and it is its shape that gives it away.
The blacksmiths that visited us on cultural night where working with the iron at the next stage, working with the raw iron or bloom to create objects like nails and such. In the Viking age and later the bloom was heated and beaten repeatedly to get the impurities out of it. After that it is ready to work into all sorts of iron artifacts.
To conclude this discussion I have added a photo of a carved description of iron working processes from another source. It is from a church in Hyllestad in Norway and has been dated to the 12th Century and shows similar working processes as have been discussed here. On the upper depiction the iron is being worked into a sword but on the lower one they are using a furnace to get the iron and cleaning the bloom.