Beeswax remnants, phase and major element chemical composition of the bronze age mould from Gaj Oławski (SW Poland)

Abstract

The recently found metal casting mould from Gaj Oławski (SW Poland) was designed for the production of socketed axes typical for later stages of the Bronze Age in Poland (ca. 1100-900 BC). This unique artefact is a half of a durable, two-piece wedge-shaped mould and measures 17.5× 7.2×4.0 cm. The surface of the mould is covered copper oxides and carbonates, and the remnant of beeswax was found on its inner surface. The metal forming mould consists of cored dendrites of Cu-dominated (Cu >96.5 wt%, up to 2.2 wt% Sn) and Cu impoverished (Cu~86.0 wt%, Sñ 9.4 wt%, some Sb, As and Ag) end compositions and volumetrically subordinate α+δ eutectoid. The "as cast" structure of the metal shows that the mould was never used for molten metal casting. Since this kind of moulds was used for mass casting of metal, the Gaj Oławski one was probably never used, and the beeswax is the remain of its coating. This is the first remain of the Bronze Age beeswax described in metallurgical context in Europe.

First Evidence of “Earth Wax” Inside the Casting Molds from the Roman Era

“…Advanced chemical analysis of three molds from the Roman era provides important information on barbaric metallurgy. Baron et al (2016) proposed that the presence of compounds related to wax in the mold points to the fact that the mold has never been used for casting [ 7 ]. However, we hypothesize that the remains of wax detected in molds #1 and #2 point to their use for the production of wax models.…”

“…Such models could be used as an intermediate stage in the production of final objects, which were produced using lost-wax casting molds [ 25 ]. Note that carbon layers in the internal parts of molds allow the direct casting of metal objects [ 7 ].…”

“…The recent chemical analysis of a metal mold belonging to Urnfield culture (1300–800/750 BC) proved the presence of carbon and beeswax in the inner part of the mold using infrared spectroscopy and gas chromatography/mass spectrometry (GC/MS). Authors hypothesize that carbon coating in the inner part of the casting mold could have been used as a layer preventing the mold from welding with the liquid metal poured into it [ 7 ]. Note that molds made of copper alloys are typical for the Barbarian region in the Roman era, where we register more findings than in the area of the former Roman Empire [ 8 ].…”

Material Genealogies: Bronze Moulds and their Castings in Later Bronze Age Britain

“…Possible traces of a carbon coating have been identified on the Isleham mould (Coombs 1971, 397–8) and on a bronze mould from France (Mohen 1978, 29). Another from Poland has beeswax residues, argued to be a fixative for a carbon dressing (Baron et al 2015), though this seems unlikely as the wax would tend to cause casting failures. For casting socketed implements, a core would be required.…”

Study of a Late Bronze Age Casting Mould and Its Black Residue by 3D Imaging, pXRF, SEM-EDS, Micro-FTIR and Micro-Raman

“…Different studies have proposed different dressing materials based on analysis of residues on Bronze Age mould artefacts: for example, one study suggested smoky flame from burning bones based on results from energy dispersive X-ray spectrometry (EDXRF), wet chemistry, Fourier transform infrared spectroscopy (FTIR), and gas chromatography mass spectrometry (GC/MS) from the black residue in a stone axe mould from Portugal [23]; another study proposed the use of beeswax based on results from FTIR and GC/MS from a black residue in a bronze axe mould from Poland [24]; finally, more recently, a blackish residue on the inner face of a Late Bronze Age mould from Portugal has been analysed by FTIR, revealing the use of clay or charcoal [14].…”