Not all the industrial related finds we encounter during our excavations are large objects. Some are miniscule and require fine sorting – with a keen eye and steady hand. We often sift through ‘magnetic matter’ that was found in environmental soil samples. A lot of this will just be a natural type of magnetic iron-rich stone, but sometimes, we find hammerscale, which is a by-product of iron smithing.
There are two main types of hammerscale, spherical and flake. The spherical type consists of small droplets of slag and looks like tiny ball-bearings. It is expelled during the initial smithing of a bloom and during welding operations. Flake hammerscale is thin and jagged in shape. It is produced when a hot object with an oxidised surface is struck by the smith, producing sparks. When found in large quantities, hammerscale can tell us that iron smithing occurred in the area and its distribution across a site can sometimes indicate what the function of a specific features were.