The Brass Nails of the Akko Tower Wreck (Israel): Archaeometallurgical Analyses

Abstract

The shipwreck designated as the Akko Tower Wreck was discovered inside Akko harbor, Israel, in 1966. It was surveyed in 1975 and 1981, and excavated in 2012-2013. Hull planks were connected to the frames by brass nails, some of which were in situ, emerging vertically from the planking, where frames had disappeared, and others were detached. The 105 nails that were retrieved were tentatively divided into two groups (A and B) according to their general shape and size. Nails sampled from each group were characterized by non-destructive and destructive metallurgical methods, including XRF, light microscopy, SEM-EDS, microindentation hardness measurements, and lead isotope analysis, in order to reveal their composition and microstructure, as well as to determine their manufacturing process and date the origin of the raw material. All nails were manufactured by casting and made of binary copper-zinc alloy: Type A with 35-36 wt% zinc, and Type B with 33-34 wt% zinc (XRF results). These compositions confirmed the preliminary typing of the nails. Their microstructure indicates that they were manufactured differently: Type A nails have Widmanstätten thin lamellae plates, and Type B nails have a-brass grains containing a dendritic microstructure. Based on their zinc and lead concentrations it is suggested that the nails were manufactured in the first half of the nineteenth century. The lead isotope analyses of the nails suggest that the raw material most probably originated in Great Britain. Hence, it is suggested that the Akko Tower Wreck is the remains of a European merchantman which sank in Akko harbor about the middle of the nineteenth century.

The 19th-Century Akko Tower Wreck, Israel: a summary of the first two excavation seasons

“…During the study of the brass spikes retrieved from the shipwreck, an attempt was made to identify the probable origin of the ores using lead isotope analysis. It is suggested that the raw material for the production of the spikes derived from a common metal source, most probably British ores from Wales or Cornwall (Cohen et al ., : 202–3). The spikes could have been manufactured from raw material that was imported from Great Britain, or made in Great Britain and shipped ready to use to the shipyard where the ship was constructed.…”

“…In addition, all spikes contained 0.5–1.1 wt% lead. Therefore, based on the zinc and lead concentrations, it is suggested that the brass spikes were most probably manufactured in the first half of the 19th century (Cohen et al ., : 199, 202).…”

An Archaeometallurgical Investigation on Metal Samples from the Chiaravalle Cross

“…In the literature, brass-based metallic nails were studied in relationship with corrosion issues (mainly in shipwreck findings [29]). The history of brass refers to the deliberate addition of zinc to copper since the first millennium BC.…”

“…Therefore, we cannot derive a strict chronological criterion to date the nail, though the low content presence of iron (up to 0.5%) and lead (less than 2%) suggests that nail 1 could have been produced in the 18th century [29]. Additionally, this nail, having a Cu/Zn ratio of 70/30, should have been produced before the use of the Muntz patent (concerning a brass metal having a Cu/Zn ratio equal to 60/40, patented in 1832 [29]).…”

Analysis of naturally etched surface of brass sheathing from a nineteenth-century shipwreck

“…Metallographic examination of ancient metal artefacts retrieved from shipwrecks reveals their microstructure and correspondingly exposes information regarding their manufacturing processes [11][12][13][14][15][16][17][18][19]. Defining moments in the development of the metallographic scientific field were in 1751, when the geologists Widmanstätten and Schreibers etched various meteorites and exposed their crystalline patterns that could be viewed with a naked eye; and in 1808 when they revealed the well-known Widmanstätten structure by macro-etching [20,21].…”