Conservation-Restoration Work on an Iron Roman Legionary's Spearhead

Conservation-restoration work was conducted in 2013 on an iron spearhead with hafting socket found during an underwater archaeological survey of the Lenovac site. The artefact is a Roman legionary's spearhead that was found below the shoreline firmly encrusted to the rocks of the embankment.

The iron spearhead was received in four fragments. In the preliminary phase of work the received fragments where inspected under magnification with the aim of the best possible analysis of damage and state of conservation and decision on the further course of conservation-restoration work. The surfaces of the fragments are covered by various corrosion products, sedimentary calcite deposits and the remains of rock the spearhead had become encrusted to. The received spearhead fragments have been preserved in an entirely mineralised state. Under the original surface layer we could see the powdery structure of the completely corroded iron – no part of the metal core had been preserved.

Iron chlorides are a component of the corrosion products and are also one of the leading causal agents of this kind of complete corrosion of the metal core of the iron spearhead. With the objective of removing chloride ions the following phase saw the combined use of pneumatic pins and electric micro motors to separate the remnants of encrusted stone from the surface of the received fragments. The spearhead fragments were then subjected to the essential desalination procedure. Following the five-month desalination period we undertook the mechanical cleaning of the iron fragments.

The mechanical cleaning procedure required particular care, as the corroded fragments were very brittle and fragile. Highly focused work under a microscope using an ultrasonic chisel and scalpels of various sizes and profiles succeeded in separating most of the sediment. Smaller localised deposits accumulated in depressions were removed by micro abrasive blasting using corundum beads of 70 to 110 ?m. Fragments were only cleaned partially because their extremely poor state of conservation meant that any further treatment could have led to the destruction of the structure. Respecting the minimal intervention principle cleaning removed only those deposits from the surface of the iron fragments that impeded their visual recognisability. After cleaning, the iron fragments were coated with a 2% solution of tannin with the aim of their active stabilisation.

Given that the original appearance of the iron spearhead was visible in the received fragments, the next phase saw their reconstruction. The cleaned spearhead fragments were first temporarily joined with cyanoacrylate. The porous connection points were then reinforced by impregnation with two-component epoxy adhesive of the industrial designation Araldit 2020. With the aim of achieving structural stability the missing sections and larger areas of damage on the surface were filled with the same resin with the addition of the appropriate pigment.

In the final phase of this conservation-restoration operation the iron spearhead was given surface protection. The final protection consisted of a mixture of reversible Paraloid B72 polymer and Cosmoloid H80 microcrystalline wax in toluene.

Antonija Jozić