Bronze Artifacts Research Articles

The Salcombe metal cargoes: New light on the provenance and circulation of tin and copper in Later Bronze Age Europe provided by trace elements and isotopes

Since the mid-1970s a Bronze Age assemblage of metal objects has been recovered from the seabed off the south Devon coast at Salcombe, southwest England. The assemblage spans two suspected shipwreck events and comprises nearly 400 pieces of raw materials and finished artefacts, primarily in copper, tin, bronze and gold. Among these are 280 copper and 40 tin ingots, by far the largest discovery of Bronze Age ingots in either metal from northwestern Europe. Research in recent years revealed the microstructural and chemical nature of the ingots and enabled some preliminary conclusions on the metals trade in Europe in the Later Bronze Age. The present study aims to extend this knowledge by determining the tin, copper and lead isotopic compositions of the ingots using HR-MC-ICP-MS. In addition, bronze artefacts (swords, rapiers, palstaves and weights) from the Salcombe site are included in the multi-proxy approach in order to investigate their history and the possible relationships between finished products and ingots. In combination with the available chemical data of previous studies, the current results of the tin metal show that most likely two tin sources in southwest Britain supplied the ore for their production. This also sheds light on Late Bronze Age tin ingots from Israel that share the same geochemical characteristics with one group of the finds from Salcombe. Although the tin in the bronzes is similar to the tin in the ingots, it is not certain that the latter were used to make the bronzes. Correlations of copper and tin isotopes and trace elements of the bronzes point to a mixing or even recycling of copper-tin alloys rather than the alloying of individual components of copper and tin. However, the copper ingots from the assemblage could have been an additional component in the mixing process given their impurity pattern and isotopic composition. At the same time, a close relationship between swords of the Rosnoën type and palstaves from the cargo is disclosed. Lead isotope ratios for their part suggest Sardinian and/or south Spanish copper ores as a source for both the copper ingots and the copper of the bronzes. This would mean long-distance metal trade in the Later Bronze Age in both cases and would provide new insights into the interpretation of the prehistoric networks in Europe.

Constraining a bioavailable strontium isotope baseline for the Lake Garda region, Northern Italy: A multi-proxy approach

The evidence of prehistoric long-distance exchange networks in northern Italy is overwhelming, attested by several finds of non-local raw materials in Bronze Age pile-dwelling settlements of Lake Garda and eastern Po plain, like amber beads and bronze artefacts. Metals are dispersed throughout Bronze Age Europe from mining communities within the Alpine regions, and possibly local artefacts, like the Peschiera-type daggers, are known from archaeological records throughout Europe. This positions the region as part of organized networks of trade and communication connecting prehistoric Europe from north to south. This, however, does not in itself indicate a similar long-distance mobility of prehistoric individuals. To investigate individual, human provenance and mobility, the strontium (Sr) isotope methodology compares strontium isotope analysis of human remains to bioavailable strontium isotope baselines characterizing the regions of interest. We present here environmentally based, multi-proxy (water, soil leachates and plants) Sr baselines from the Lake Garda region. Our results show two separate baselines, roughly corresponding to the geographical distribution of rock types and erosional products thereof. One baseline is valid for the Lake Garda region, where Mesozoic carbonates are a dominant surface-near strontium source, and for the central Po plain north of River Po. We constrain this to 87Sr/86Sr = 0.7088 ± 0.0014 (2σ; n = 44) when including 9 compatible samples reported previously. The second Sr-baseline is valid for Alpine areas dominated by magmatic (basalts excluded) and metamorphic bedrock around the Fersina valley. We constrain this to 87Sr/86Sr = 0.7146 ± 0.0058 (2σ; n = 22) when including 11 compatible samples reported in previous studies. The baselines are compatible with previously reported results of other Sr proxies such as snails, archaeological fauna, and agricultural soils and products from the region.

Micro-structural and micro-chemical investigation of Samnite high-tin bronze cuirass discs: ancient metallurgy in central Italy

In the present study, micro-structural and micro-chemical investigation of archaeological bronze artefacts provided new insight about the metallurgical manufacture of defensive weapons by the Samnite’s metalsmiths in central Italy from the archaic necropolis of Barrea (AQ) and Torrebruna (CH). In particular, the metallurgical features, the chemical composition and the manufacturing process of Cu-based high-tin alloys used to produce cuirass discs were investigated. These artifacts were used to protect the warrior’s heart (i.e. the kardiophylaches) but were also and more importantly a distinctive sign of rank and role of warriors of the archaic age (VI BC). The Samnite cuirass discs are multi-material artifacts made of a decorated bronze central part with a complex metallurgical structure, due to the presence of different Cu-Sn phases, and a surrounding iron cladding to support the disk. These discs were studied by different surface and bulk techniques, namely Optical Microscopy (OM), Field Emission Scanning Electron Microscopy coupled with energy dispersive X-ray microanalysis (FE-SEM-EDS), X-ray Diffraction (XRD) and Infrared Spectroscopy (FTIR). The combined use of these techniques proved the high technological level of the Samnite metallurgists. In fact, their particular composition, having an uncommon high content of tin, made their manufacturing process difficult because of the intrinsic brittleness of the alloy. This work disclose the ability of Samnites people to successfully manipulate fragile high tin bronze alloys by inducing temporary phase changes and, thus, facilitating the mechanical shaping of the artifact.

Scanning electron microscopy and energy dispersive spectrometry analyses of ancient bronze artefacts of the Urartian period from Yegheghnadzor region, Armenia.

The results of the analysis on some fragments of bronze belts and a bowl discovered from southwestern Armenia, Yegheghnadzor archaeological site, are discussed. The samples are dated to the 7 and 6 BCE from the Urartian period. The artefacts were corroded, and a multilayer structure was formed. To study the stratigraphy of layers and their composition, the samples were analysed using scanning electron microscopy and energy dispersive spectrometry (scanning electron microscopy (SEM)-EDS) and optical microscopy techniques. The bronze finds appear with the typical incrustations, rich in alloy alteration compounds. Concentrations of copper and tin in the alloys were quantified by SEM-EDS: The pattern and the percentage of the alloy are the same for the belts. Regarding the bowl sample, it is constituted by two foils, perfectly in contact but different in colour, thickness and composition. The results evidenced that only two elements participate in forming alloy composition in the samples: Cu and Sn. The tin content is variable from 7.75% to 13.56%. Other elements such as Ag, As, Fe, Ni, P, Pb, Sb and Zn are lower and more than 1% and can be considered as impurities.

Analysis of the CHARM Cu‐alloy reference materials using excimer ns‐LA‐ICP‐MS: Assessment of matrix effects and applicability to artefact provenancing

AbstractExcimer nano‐second laser ablation inductively coupled plasma mass spectrometry (ns‐LA‐ICP‐MS) is an important tool in chemical characterization of Cu alloys. However, variable matrix‐induced elemental fractionation in Cu alloys poses a significant challenge. We systematically investigate this issue by analysing the Cultural Heritage Alloy Reference Material Set (CHARM) of Cu alloy targets. The extent to which silicate glass reference materials can be used when analysing Cu alloy targets is determined, as is the optimal internal standard, for a wide range of Cu alloy compositions. Analyses were further optimized by quantitative assessments of the use of CHARM end‐member materials as external standards for other CHARM Cu alloy targets. The variable magnitude of the observed matrix effects is most readily explained by variations in Cu/Zn ratios and resulting differences in melting and boiling points, compared with external reference materials, making the Zn‐rich Cu alloy targets most prone to matrix effects. With the correct choice of an external matrix‐matched standard (Pb‐rich CHARM reference material 32X LB14F) and internal element standardization, an accuracy of < 20% can be achieved for virtually all elements of interest in brass and bronze artefacts, which is a significant improvement compared with the use of glass external reference materials.

The complex atmospheric corrosion of α/δ bronze bells in a marine environment

• Long term corrosion of a high-tin bronze bell in a steeple under marine atmosphere. • A corroded high-tin α/δ alloy Cu-Sn-Pb: comparaison with ancient buried artefacts. • Complex alteration due to environment, shocks and vibrations of bells. • Particular pitting corrosion of α/δ alloy. • Hypothesis of a micro-infiltrating alteration scenario of the α/δ bronze bell. α/δ bronze bells are heritage materials subject to corrosion. The alteration of a high-tin bronze bell casted in the 1930s and exposed to a marine environment in a steeple was studied. The ternary bronze (Cu-Sn-Pb) alloy displays inclusions and a porosity due to micro-shrinkages and poor gas evacuation. This altered bronze is characterized to (1) assess the influence of the manufacturing techniques and (2) hypothesize a micro-infiltration scenario of its alteration. After exposure to the atmosphere, a transformed superficial medium overlaying layers of atacamite-paratacamite-cassiterite appears. Under them, the corrosion of the α dendritic structure and α/δ eutectoid characteristic of bronze bell is evidenced. The α pitting has a pronounced multilayered structure of cassiterite and cuprite-copper chloride, whereas the δ corrosion is composed of cassiterite and traces of cuprite. To understand better the lead impact on corrosion process, samples of the alloy were exposed in the laboratory to a synthetic marine solution. The long-term corrosion behavior of the studied bell shows some similarities to those of other high tin bronze artefacts. The hypothesis of a corrosion scenario emphasizes the importance of the bells manufacturing techniques, α/δ structure of the ternary Cu-Sn-Pb alloy, and infiltrating networks of environmental fluids.

Is it hot enough? A multi-proxy approach shows variations in cremation conditions during the Metal Ages in Belgium

Studies of funerary practices provide information about many aspects of death in past societies. However, only limited archaeological evidence documents the circumstances under which cremations occurred and the person(s) who were performing the funerary rituals. Lying at the border between Atlantic and Continental cultural traditions, the Scheldt and Meuse basins of Belgium represent a unique location to investigate variations in ancient pyre technology and body management, as well as the transfer of knowledge related to cremation techniques during the Metal Ages (ca. 2100-52 BCE). The combined use of Fourier Transform Infrared spectroscopy, and carbon and oxygen isotope analysis of different skeletal elements from cremation deposits from four archaeological sites clearly shows differences between the Meuse and Scheldt basins. Different wood availability or selection, and variations in the skills and/or experience of the cremation operator may explain these results. These observed differences are likely linked to ways in which cremation was performed in the two basins, indicating that during the Metal Ages, burning processes were not homogeneous in the Belgian region. Instead, cremation practices appear to align with the different cultural influences also observed in ceramics and bronze artifacts from the same time period. These observed differences in funerary practices between the two basins in Belgium show the immense potential of combining infrared and carbon and oxygen isotope analyses to investigate cremation rituals in any period and region around the world.

Micro-Stratigraphical Investigation on Corrosion Layers in Ancient Bronze Artefacts of Urartian Period by Scanning Electron Microscopy, Energy-Dispersive Spectrometry, and Optical Microscopy

The results of the analysis on some fragments of bronze belts and a bowl discovered from southwestern Armenia at the Yegheghnadzor archaeological site are discussed. The samples are dated to the 7–6th millennium BCE from the Urartian period. The artefacts were corroded, and a multilayer structure was formed. To study the stratigraphy of layers and their composition, the samples have been analyzed using SEM-EDS (Scanning Electron Microscopy, Energy-Dispersive Spectrometry) and OM (Optical Microscopy) techniques. The bronze finds appear with the typical incrustations rich in alloy alteration compounds. Concentrations of copper and tin in the alloys were quantified by SEM-EDS: the pattern and the percentage of the alloy are the same for the belts. Regarding the bowl sample, it is constituted by two foils perfectly in contact but different in color, thickness, and composition. The results evidenced that only two elements participate in forming the alloy composition in the samples: Cu and Sn. The tin content is variable from 7.75% to 13.56%. Other elements such as Ag, As, Fe, Ni, P, Pb, Sb, and Zn make up less than 1% and can be considered as impurities.

An old problem in a new light: Elemental and lead isotopic analysis of Luristan Bronzes

The emergence and provenance of the Luristan Bronzes has been a subject of interest for many decades. This paper presents the results of elemental and lead isotopic analysis of a series of Luristan Bronzes discovered from recent excavations in the Sangtarashan sanctuary, as well as an extensive comparative study on technology and provenance of the Luristan Bronzes. This study was performed in order to better understand tin bronze production technology in the Luristan region during the Iron Age. It focuses on the artefacts themselves, as no mining or production evidence has been discovered in Luristan so far. For this purpose, 46 samples from different pieces of thin sheet vessels from Sangtarashan were analysed by inductively coupled plasma-optical emission spectroscopy (ICP-OES) for their elemental composition and by multi-collector inductively coupled plasma-mass spectroscopy (MC-ICP-MS) for their lead isotopic composition. The results of elemental analysis showed that tin bronze with variable tin content was used to produce these artefacts. The comparative study of the alloy composition also shows that tin bronze may have been the main material to produce ritual artefacts during the Iron Age of western Iran. Furthermore, the lead isotope ratios of the Sangtarashan artefacts partially overlap with those of different copper ore deposits on the Iranian Plateau, including deposits close to Luristan (such as Deh Hosein) and ore deposits further away, in central and eastern Iran. In fact, the results revealed that it is not possible at this stage in the research to identify one specific ore deposit or region as the source of copper for tin bronze metallurgy during the Iron Age of Luristan. Thus, the research suggests that ancient metalworkers apparently used different copper sources to produce the bronze artefacts specific to the region of Luristan in western Iran.

The Study of Non-Ferrous Metal Artifacts of the Early Iron Age and Medieval Cultures in the Western Amur Basin

We describe the morphological and quantitative characteristics, and the elemental composition, of 23 bronze artifacts, seven silver ones, and a gold adornment, spanning the period from late 11th century BC to 15th century AD. These items (adornments and tools) belong to the Uril and Talakan cultures of the Early Iron Age, Mikhailovka, Mohe, and Central Asian cultures of the Early Middle Ages, and the Ducher culture of the Late Middle Ages. Elemental analysis of the bronze items at the SB RAS Institute of Nuclear Physics Siberian Center for Synchrotron and Terahertz Radiation Station of Local and Scanning X-Ray Fluorescence Elemental Analysis showed that over about 2.5 thousand years, tin-lead or lead-tin bronze was used for manufacture. Also, the best convergence of concentrations of chemical elements for Talakan and Mikhailovka artifacts testifies to evolutionary continuity between the Talakan and Mikhailovka cultures. Analysis of the elemental composition of Mohe silver and gold items from the Amur basin was carried out for the first time, revealing the high purity of precious metals used for manufacturing early medieval jewelry.

Multi-proxy analyses reveal regional cremation practices and social status at the Late Bronze Age site of Herstal, Belgium

The funerary Bronze Age culture in the Belgian part of the Meuse valley is poorly understood due to the challenging nature of cremation deposits that dominate the archaeological record. Only a few sites were analysed in that region, limiting the possibilities to reconstruct the development of Bronze Age populations in Belgium. Due to its good preservation and detailed excavation reports, the site of Herstal (Belgium) offers a unique opportunity to finally gain new insights into the life and death of those buried in the Meuse Valley during the Late Bronze Age. A total of 21 graves were analysed using a multi-proxy approach, combining grave typology, osteoarchaeology, strontium isotope ratios (87Sr/86Sr), and radiocarbon dating. The 87Sr/86Sr results show that the individuals of Herstal most likely used a variety of local food supplies while having interactions with other populations in and beyond the Meuse Valley, as demonstrated by the bronze artefacts and ceramics displaying clear influences from Germany, Southern Netherlands, and North-West France. The cemetery most likely shows a local burial style with the presence of two (or even three) individuals in several cremation deposits containing a number of privileged individuals who had access to bronze trading networks.

Pharaoh’s copper: The provenance of copper in bronze artifacts from post-imperial Egypt at the end of the second millennium BCE

The source of Egypt’s copper supply during the Third Intermediate Period (1070–664 BCE) is largely unknown. Here we present new data from chemical (elemental) and lead isotope (LI) analysis of royal Egyptian artifacts of the 21st Dynasty (ca. 1010 BCE) – a period which until now was represented in the LI record only by a single artifact. Our finds identify the source of the copper in the Arabah region providing a basis for our historical reconstruction of the copper exchange network in the southern Levant at the turn of the first millennium BCE. We also analyzed two objects from the 24th and 25th Dynasties (8th c. BCE), which revealed a marked change in Egyptian copper metallurgy in both the composition (from Cu with traces of Sn to leaded copper with traces of As) and the supply chain (the Arabah ores are excluded). As the sampling involved museum artifacts, we performed X-ray imaging as a means to avoid sampling of any later metallic modifications and ensure the correct sampling process.

Laser cleaning on bronze artefacts by the XeCl laser

In this paper, bronze samples from Bam Arg World Heritage for laser cleaning with XeCl laser is investigated. The sample is analyzed before and after laser cleaning by XRD, DAX, SEM and PIXE methods to determine their surface impurities then optimum conditions such as the repetition rate and number of laser pulses obtain for laser cleaning.

A new application of Fiber optics reflection spectroscopy (FORS): Identification of “bronze disease” induced corrosion products on ancient bronzes

Fiber Optics Reflectance Spectroscopy (FORS) has been widely used in the field of cultural heritage for material identification. Nevertheless, it had been rarely applied in the study of bronze corrosion products. This paper aims at exploring the potential of FORS on corrosion products analysis, proposing it as an innovative non-destructive technique for the condition assessment of bronze artefacts in museum collections. A gilded bronze statue “Vajrasattva Bodhisattva” dated to the Ming dynasty (A. D. 1368-1644) from National Museum of China was investigated. The in-situ FORS analysis was conducted on 36 points, revealing copper trihydroxychloride (atacamite/clinoatacamite) and chalconatronite as two major types of corrosion products. This result was double-confirmed by Raman and XRD analyses of 10 samples taken from these points. It proves that FORS is a very promising technique for non-destructive in-situ detection of chloride-bearing bronze corrosions. It may revolutionize the way of screening artefacts with bronze disease, helping conservators get the distribution “map” of different bronze corrosion quickly and comprehensively, and making appropriate treatment proposals accordingly.

Application of µ-Raman spectroscopy to the study of the corrosion products of archaeological coins

<p>In this paper, a study of the corrosion products formed on archaeological bronze artefacts excavated in Tharros (Sardinia, Italy) is presented. The investigation was carried out by means of the combination of different analytical techniques, including optical microscopy, micro-Raman spectroscopy (µ-RS), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and X-ray diffraction. The artefacts under study are three bronze coins from the Phoenician–Punic period that are deeply corroded due to the chloride-rich soil of the Tharros excavation site. µ-Raman spectroscopy was chosen to investigate the corroded surfaces of the artefacts because it is a non-destructive technique, it has high spatial resolution, and it makes it possible to discriminate between polymorphs and correlate colour and chemical composition. Through µ-RS, it was possible to identify different mineralogical phases and different polymorphs, such as cuprite (Cu<sub>2</sub>O), copper trihydroxychloride [Cu<sub>2</sub>Cl(OH)<sub>3</sub>] polymorphs, hydroxy lead chloride laurionite [PbCl(OH)] and calcium carbonate polymorph aragonite. The experimental findings highlight that micro-Raman spectroscopy can be used to provide further knowledge regarding the environmental factors that may cause the degradation of archaeological bronzes in soil.</p>

A Study on the Microstructure and Corrosion Characteristics of Early Iron Age Bronze Mirrors Excavated from the Korean Peninsula

Bronze mirrors, considered important grave goods, were widely used before glass mirrors in ancient times. Most excavated bronze artifacts are covered with corrosive materials and lose their original colors. More importantly, identifying corrosion characteristics and the manufacturing techniques used for these artifacts are essential for proper artifact preservation. In this study, Early Iron Age bronze mirrors excavated from the Korean Peninsula were examined to determine their microstructures, corrosion characteristics, and production techniques using various analytical methods, such as Micro-Raman spectroscopy and field emission electron probe microanalysis. As a result, sulfides containing iron suggested chalcopyrite use during production or that the sulfides originated from copper, iron, and sulfur residual matte. The analysis also detected corrosion layers with high tin oxide (SnO2) levels and selective corrosion in the α + δ eutectoid phase on the artifact’s surface. In the corrosive layer, cuprite, malachite, and cassiterite corrosion products were detected, and nanocrystalline SnO2 was identified as a characteristic of long-term soil erosion. Identifying these artifacts’ corrosion characteristics and manufacturing techniques is essential and can greatly contribute to proper artifact preservation.

Quantitative determination of antimony in archaeological bronze artefacts by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a reliable, fast and micro-destructive diagnostic method for qualitative and quantitative analysis of a variety of materials. In this paper, we report the results of quantitative determination of antimony in four archaeological bronze artefacts analyzed by means of LIBS. For the purpose of this study, an approach of multi-elemental quantitative LIBS analysis is proposed, based on the use of an element with known concentration as an internal standard and measurement of the spectral lines intensities of the internal standard and the element with unknown concentration. An important plasma parameter which is included in the quantitative analysis is the excitation temperature as determined by the Boltzmann plot method. The quantity of antimony in the bronze artefacts obtained by means of the proposed LIBS approach is between 1.49% and 3.13%.

Imports or imitations?: Scientific and typological analysis of the bronze artefacts at the Moutuo Archaeological Site, Sichuan, China*

The typological and scientific analysis of bronze artefacts has been widely applied to the issue of local production versus important, which can be further linked to the long‐distance trade exchange and movement of raw materials, technology and people. Bronze artefacts bearing stylistic features of different regional origins have been discovered at the site of Moutuo in Sichuan, south‐west China. This study investigates the metal provenance of these artefacts by using the impurity patterns of the Oxford system. By combining the Pb isotopic data, it is feasible to distinguish the locally produced objects from those importations. This study contributes a detailed case study to the wider question of the movement of metal in south‐west China between the Late Bronze Age and Early Iron Age.

Biopassivation Method for the Preservation of Copper and Bronze Artefacts

A biopassivation method has been proposed as a new ecological and sustainable solution for preserving copper-based artefacts using selected microorganisms. This technology is based on the natural capacity of some fungi to form copper oxalates on the corroded surface of copper alloys. Existing unstable and pulverulent corrosion products are converted into an insoluble and chemically stable biopatina that provides the treated surfaces with a stabilization of the corrosion process and an aesthetically attractive green color. This treatment allows to stabilize the active corrosion induced for example by copper chlorides and to prevent green staining of surrounding materials (stone pedestal, wall…) due the leaching and loss of pulverulent and water-soluble corrosion products (i.e. copper sulfates). The behavior and performance of the proposed treatment have been followed during natural aging procedures, which have shown that this method stabilizes the corrosion process while having less chromatic variation compared to more traditional protective systems. The application protocol was then validated on real cases such as outdoor sculptures and archaeological objects. Based on these results, a ready-to-use kit is now proposed to conservators.

Two bronze objects of Western origin in the Saharna microregion, Rezina district, Republic of Moldova

In the Saharna microregion (Rezina district, Republic of Moldova), four settlements and one burial attributed to the Holercani-Hansca culture are currently known. In the settlements Saharna Mare / “Dealul Mănăstirii” and Saharna “Rude”, a bronze hairpin of Ösennadel type and a crescent pendant with vertically perforated shank were recently discovered. Both objects have many analogies in Transylvania as well as in Central Europe, being dated within the period Bz D – Ha A1. Along with the finds from Saharna microregion, in the area of the Holercani-Hansca culture, in the sites of Calfa, Holercani, Coșnița and others, other bronze artifacts are known, also of Western origin and having the same chronological markers. Thus, the presence of these objects denotes the connections of the communities from the Prut-Dniester area with Transylvania and Central Europe.