Apart from Roman coins from Binchester we have also started working on the iron objects from Nevern Castle in Wales. The excavations began in 2008 and are still ongoing. The archaeology has revealed that the castle was built of earth and timber in the early 12th century and has continuously been going through developmental changes. The surviving remains of Nevern Castle preserved valuable evidence of life in 12th century and onwards.
Most of the excavated iron work is covered in thick layers of corrosion and it is practically impossible to define or interpret any of it. This really emphasizes how important x-radiography is in conservation. The use of x-radiography allows us to assess the conditions of objects and examine technological features, e.g. shape, extent of corrosion, construction, wear marks or working marks. During our practical with Vicky we learned how to successfully take and develop x-rays, and during the following weeks we sat down with Dr Caple to interpret our results. It was incredibly exciting to see what was hiding underneath the corrosion. A lot of the objects were just nails; however we also had a lot of horseshoe nails, a complete horseshoe, arrowheads and a few ‘mystery’ objects which we will examine in the following weeks.
Once we identified our x-rayed objects we were then introduced to air abrasion, which is a widely used method to clean the corrosion off archaeological iron and to reveal surface details on an artefact. With the air abrasion method, air and an abrasive are discharged through a pen-like device onto any corrosion covering an artefact. The corrosion is worn away by means of friction. We have used Aluminium Oxide as our abrasive; however other products can be used, for example tiny glass beads.
Air abrading takes a lot of precision and patience and a conservator has to be aware of the different corrosion layers occurring in metal objects in order to remove them correctly without disturbing the original surface. It was quite a challenge; however the results were very satisfying. We are looking forward to conservation of the more complicated iron objects as so far we have only practiced on horseshoe nails.
Sandra.