We started making the replica axe from spongy blooms of bog ore iron. This had to be refined and turned into forgeable iron, which proved to be an extensive job.
Iron refining and the making of steel
These articles describe in detail how we went about refining the bog iron to make it suitable for forging and how we produced hardenable steel for the cutting edge.
With a moderate supply of air, re-smelting is a method used to consolidate and process blooms of iron, without making them into steel. This is a highly efficient processing method, but was it in use at the time of the Vikings?
As we set out to transform iron into steel, the first method we explored was the re-smelting of iron with an ample supply of air, raising the temperature high.
The second steel-making method we tried out, involved infusing solid iron with carbon gas while being heated within a clay package. This method is called pack carburising or case hardening.
Eventually, after a few rounds of steel-making for the cutting edge of the axe, we realised that some of the bog ore blooms in fact incorporated large chunks of carbon-rich steel.