Bronze Artifacts Research Articles

Chitosan-based coatings for corrosion protection of copper-based alloys: A promising more sustainable approach for cultural heritage applications

The attractive physicochemical properties of chitosan make its derived materials promising candidates for the reliable and sustainable corrosion protection of metallic substrates. In this work, chitosan-based coatings embedding different corrosion inhibitors, i.e. benzotriazole (BTA) and mercaptobenzothiazole (MBT), were investigated for the protection of copper-based alloys, with the aim to extend their application to the preservation of works of art exposed to indoor atmosphere. The composition of the formulations was optimized paying particular attention to their potential application in the field of cultural heritage. To assess the efficacy of the coatings, tailored accelerated corrosion tests were carried out on bare and coated bronze substrates. Coated and uncoated alloy disks were characterized before and after corrosion treatments by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Moreover, an image analysis protocol was defined to evaluate the extent of surface modifications after degradation treatments. The obtained results revealed that the chitosan-based coatings containing BTA and MBT fulfil the aesthetic criteria required in the field of cultural heritage and are able to inhibit the corrosion of bronze alloys. It is worth noting that a synergic effect between the chemical protection provided by the inhibitors and the physical one provided by the polymer matrix was observed. Our findings demonstrate that the developed systems are suitable for a reliable and more sustainable protection of indoor bronze artefacts, thus representing a promising alternative to commercial products and particularly taking advantage from the use of non-harmful solvents for their application and removal.

Issues of The Usability of Copper Ore (Chalcopyrite) From Bălan for Ustensiles Production in The Bronze Age

Abstract Archaeological publications connect the raw material used for the production of copper and bronze artifacts discovered during the excavations carried on in Szeklerland to the use of the chalcopyrite from the Bălan copper ore deposit. So far, this assumption has not been confirmed by concrete evidence. Men of the Bronze Age can’t possibly have had knowledge of the metallurgy of sulphide-type copper ores such as chalcopyrite. Applying investigations based on spectroscopy, the Bronze Age use of chalcopyrite from Bălan could be either confirmed or refuted, the new data throwing more light on the provenance of the bronze artifacts discovered in the Szeklerland.

Investigation of archaeological metal artefacts by laser-induced breakdown spectroscopy (LIBS)

In this work, laser-induced breakdown spectroscopy was applied to determining the elemental composition of a set of ancient bronze artefacts dated from the Late Bronze Age and Early Iron Age (14th – 10th century BC). We used a Nd:YAG laser at 1064 nm with pulse duration of 10 ns and energy of 10 mJ and determined the elemental composition of the bronze alloy that was used in manufacturing the samples under study. The concentrations of tin and lead in the bulk of the examined materials was estimated after generating calibration curves for a set of four standard samples. The preliminary results of the analysis will provide information on the artefacts provenance and on the production process.

Interface thermal conductance characterization by infrared thermography: A tool for the study of insertions in bronze ancient Statuary

In this paper, a new method based on the use of infrared thermography is proposed for the characterization of repairs and inserted parts on ancient bronzes. In particular, the quality of the contact between different kind of insertions and the main body of bronze statues is investigated by analysing the heat conduction process occurring across the interface between them. The thermographic results have been used to establish the nature of these inserted elements and the way they have been coupled to the main body of the statue during and after the manufacturing process.A model for the heat conduction based on the numerical finite elements method has been applied to compare the obtained results to the theoretical predictions. Measurements have been first carried out on test samples and then in the field on the Boxer at Rest (Museo Nazionale Romano in Rome), a masterpiece of the Greek Statuary, which contains a large variety of inserted items and repairs which are typical of the manufacturing process of bronze artefacts in general.

Ural-European Parallels in the Eneolithic and the Bronze Age: Identification of Migrations (Methodological Approach)

The article is devoted to two episodes that allow us to speak about the presence of long-distance connections and contacts (or migrations) between the Urals and Europe during the Eneolithic and Bronze Age. The earlier Eneolithic contacts are represented by the Ural megaliths, which have parallels in Northwestern Europe. Later contacts are reflected in Bronze artifacts of the Seima-Turbino type and in tin alloys penetrating to Central and Western Europe from the east in the Late Bronze Age.

Did China Import Metals from Africa in the Bronze Age?

The origins of the copper, tin and lead for China's rich Bronze Age cultures are a major topic in archaeological research, with significant contributions being made by archaeological fieldwork, archaeometallurgical investigations and geochemical considerations. Here, we investigate a recent claim that the greater part of the Shang‐period metalwork was made using metals from Africa, imported together with the necessary know‐how to produce tin bronze. A brief review of the current status of lead isotopic study on Shang‐period bronze artefacts is provided first, clarifying a few key issues involved in this discussion. It is then shown that there is no archaeological or isotopic basis for bulk metal transfer between Africa and China during the Shang period, and that the copper and lead in Shang bronze with a strongly radiogenic signature is not likely to be from Africa. We call for collaborative interdisciplinary research to address the vexing question of the Shang period's metal sources, focusing on smelting sites in geologically defined potential source regions and casting workshops identified at a number of Shang settlements.

Application of Kernel Density Estimates to Lead Isotope Compositions of Bronzes from Ningxia, North‐West China

The aim of this paper is to apply kernel density estimates (KDEs) to the visualization and interpretation of lead isotope data from bronze assemblages found along the northern border of central China, here designated as the Arc. New lead isotope analyses of 30 leaded tin–bronze artefacts from the Wangdahu cemetery (c.500–300 bc) in the Ningxia Hui Autonomous Region, north‐west China, provide the basis for the discussion. By using multivariate KDEs and the calculated likelihood of the overlap, the present work shows that the Wangdahu objects feature a unique linear array of isotope ratios, representing an important element of overall bronzes from the Arc in the first millennium bc. This characteristic isotope signature is fundamentally different from that of Dajing ores in north‐east China, as well from that of early Qin bronzes in Shaanxi and Gansu provinces. This suggests that a variety of metal resources were utilized by peoples living in the Arc. The KDE approach thus proves effective at presenting and comparing lead isotope data.

The features as a county of Chu State: chemical and metallurgical characteristics of the bronze artifacts from the Bayilu site

Twenty bronze samples from the Bayilu site (Nanyang City, Henan Province) were analyzed and compared to contemporaneous bronze artifacts. This study attempts to find out metallurgical and isotopic characteristics of the Bayilu bronzes. The results suggest the bronze artifacts are Cu-Sn-Pb alloys. Most of the bronzes were cast without secondary processing. Five samples were forged and annealed after casting, and three samples might be annealed and forged. Lead isotope data of the samples display a large range. High amount of Ag and Sb may be a trace elemental signature of the Bayilu bronzes. The major elements, the manufacture process, the lead isotope ratios, and the trace elements all have diversities. Compared to contemporary bronze artifacts, some of the samples show characteristics of the bronzes of Chu State. It indicates Shen County might be involved in the political and economic system of Chu State. It is also possible that some of the Bayilu bronzes are imported from somewhere outside Chu State. Combined with the historical background of Shen County, the diversity of the bronzes may be a signature as a border county.

The Analysis and Discussion on the State of E Bronze Artifacts Unearthed From Tomb M4 at Yangzishan, Suizhou City

The Analysis and Discussion on the State of E Bronze Artifacts Unearthed From Tomb M4 at Yangzishan, Suizhou City

Experimental design of the Cu-As-Sn ternary colour diagram

The aesthetic appearance of metals has long been recognised in archaeometric studies as an important factor driving inventions and innovations in the evolution of metal production. Nevertheless, while studies of ancient gold metallurgy are well supported by modern research in colour characteristics of gold alloys, the colour properties of major prehistoric copper alloys, such as arsenical copper and tin bronzes, remain either largely understudied or not easily accessible to the western scholarship. A few published studies have already indicated that alloying and heat treatment change the colours of copper alloys, although they are mainly based on examples of prehistoric tin bronze objects and experimental casts. Here we present a procedure for building the Cu-As-Sn ternary colour diagram, starting with experimental casting of 64 binary and ternary alloys in this system. We used two types of information to produce two different ternary colour diagrams: one based on photographs of the samples, and the other based on the colorimetric measurements. Furthermore, we developed a procedure for creating a graphic representation of colours in the Cu-As-Sn ternary diagram using QGIS. As an initial case study, we plotted the composition of the world's earliest tin bronze artefacts; the graphic representation further supports claims about the importance of a golden hue for their invention and demand, c. 6500 years ago. We argue that the presented colour diagrams will find wide use in future investigations of aesthetics of prehistoric copper alloys.

Portable XRF on Prehistoric Bronze Artefacts: Limitations and Use for the Detection of Bronze Age Metal Workshops

Portable XRF on Prehistoric Bronze Artefacts: Limitations and Use for the Detection of Bronze Age Metal Workshops

The excavation of the Dadianshan Cemetery in Changning, Yunan

AbstractIn 2012, 198 burials were excavated in the Dadianshan Cemetery site in Changning County, Yunnan. The striking differences in burial structure and grave goods of these burials suggest that the cemetery was used by two different ethnic groups. The structure of the burials can be classified into earthen cave burials, earthen pit burials and urn burials. The first type has never been seen in the Bronze Age archaeology of Yunnan. They yielded rich assemblage of grave goods predominantly comprising bronze artifacts, the main types of which were sabers, spearheads, bracelets, yue-battle axes, swords, buckles, etc. They were likely associated with the ancient Ailao people of the late Spring-and-Autumn to late Warring-States Periods. The second burial type was prevalent in Bronze Age Yunnan. These burials yielded small number of or no grave goods. In addition to bronze, the grave goods assemblage also comprised of iron, bimetallic, stone and pottery artifacts. They were likely associated with the Di and Qiang people during the mid Warring-States Period to the late Western Han Dynasty.

Újabb bográcslelet Erdőszentgyörgyről (Sângeorgiu de Pădure, Ro)

The paper presents the bronze cauldron discovered in 2009 in the vicinity of Sângeorgiu de Pădure. After specifying its typological characteristics, other bronze artefacts from its surroundings, the find spot, the characteristics of the landscape and the role played by the cauldron within this landscape are also taken into consideration.

On smelting cassiterite in geological and archaeological samples: preparation and implications for provenance studies on metal artefacts with tin isotopes

Tin isotope ratios may be a useful tool for tracing back the tin in archaeological metal artefacts (tin metal, bronze) to the geological source and could provide information on ancient smelting processes. This study presents the results of laboratory experiments, which reduced (smelted) synthetic stannic oxide, natural cassiterite and corroded archaeological tin and bronze objects. The overall aim of the study is to find a reliable method for the decomposition of tin ores and corrosion products in order to determine their tin isotopic composition, and to explore possible effects on the tin isotope ratios during pyrometallurgy. We focused on five methods of reduction at high temperatures (900–1100 °C): reduction with CO (plain smelting), reduction with KCN/CO (cyanide reduction), reduction with Na2CO3/CO, reduction with Cu/CO (‘cementation technique’) and reduction with CuO/CO (‘co-smelting’). The smelting products are analysed by means of optical and scanning electron microscopy as well as X-ray diffraction, while their isotope composition is determined with a high-resolution multi-collector mass spectrometer with inductively coupled plasma ionisation. The results show that all five methods decompose synthetic stannic oxide, cassiterite and corrosion products. Ultimately, reduction with KCN is the best solution for analysing tin ores and tin corrosion because the chemical processing is straightforward and it provides the most reproducible results. Reduction with Na2CO3 and copper is an alternative, especially for bronze corrosion, but it requires laborious chemical purification of the sample solutions. In contrast, evaporation of tin and incomplete alloying during plain smelting and co-smelting can cause considerable fractionation among smelting products (Δ124Sn = 0.10 ‰ (0.03 ‰ u−1)). A less precise and even inaccurate determination of the tin isotopic compositions of the tin ores would be the consequence. However, the results of this study help to evaluate the possible influence of the pyrometallurgical processes on the tin isotope composition of tin and bronze artefacts.

Non-destructive characterization of archeological Cu-based artifacts from the early metallurgy of southern Portugal

In this study, Monte Carlo (MC) simulations combined with energy dispersive X-ray fluorescence (EDXRF) spectroscopy have been used to characterize non-destructively a collection of Cu-based artifacts recovered from two archeological sites in southern Portugal: (a) the Chalcolithic E.T.A.R. site of Vila Nova de Mil Fontes and (b) the Middle Bronze Age site of Quinta do Estacio 6. The metal artifacts show a multilayered structure made up of three distinct layers: (a) brownish carbonate soil-derived crust, (b) green oxidized corrosion patina, and (c) bulk metal. In order to assess the reliability of the EDXRF-based Monte Carlo simulations to reproduce the composition of the alloy substrate in archeological bronze artifacts without the need to previously remove the superficial corrosion and soil derived patinas, EDXRF analysis together with scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) was also performed on cleaned and patina-/crust-coated areas of the artifacts. Characterization of the mineralogical composition of the corrosion products in the surface patinas was further determined by means of X-ray diffraction (XRD). Results suggest that the adopted EDXRF/Monte Carlo protocol may represent a safe and fast analytical approach in the quantitative characterization of the bulk chemical composition of Cu-based metal artifacts even in the presence of fairly thick corrosion patinas and/or soil-derived encrustations at the surface of the archeological objects.

Metalworking at Megiddo during the Late Bronze and Iron Ages

Metalworking at Megiddo during the Late Bronze and Iron Ages

Cu-Sn-Pb Alloy Fabricated by Powder Metallurgy and Its Application for Standard Curve Establishment of Portable X-Ray Fluorescence Instrument for Alloy Analysis on Bronze Relics

ABSTRACT One of the most important non-destructive methods for on-site analysis of bronze artifacts is portable X-ray fluorescence (XRF). However, bronze artifacts are usually heterogeneous in composition due to, among other things, the segregation of lead, which is hard to be eliminated through annealing treatments. In the present work, Cu-Sn-Pb alloys with homogenous composition and microstructure is fabricated by powder metallurgy technique. The suitability of the standard curve using Cu-Sn-Pb alloys by powder metallurgy as the standard samples for XRF on the analysis of bronze artifacts is evaluated. It is shown that this proposed method can be transferred to portable XRF to acquire accurate on-site composition information of bronze artifacts.

The bronze artifacts from the Yejiashan site and the political presence of the Zhou dynasty in the middle Yangtze Plain: an application of lead isotope analysis

Lead isotope ratios of 15 Chinese bronze artifacts from the Yejiashan site (Suizhou City, Hubei Province) were analyzed and compared with copper ores across China. This study attempts to provide a new perspective to discuss the role that Zeng State played among all the vassal states in the early Zhou dynasty (ca. 1046–977 BC). The political presence of the Zhou dynasty in the middle Yangtze Plain is another main content of this paper. The lead isotopic characteristics of Chinese bronze artifacts between different historical periods are also in the scope of the study. By comparison, the lead isotopic ratios of the tested bronzes and copper deposits in the north Jiangxi Province show numerous overlaps. It indicates that the tested bronzes might have a single ore source, and this source was in the south of the Zhou dynasty. Combined with history and archaeological records, it is highly likely that the middle Yangtze Plain might be a part of the Zhou dynasty since the very beginning. Moreover, Zeng State might have a great influence in the ancient middle Yangtze Plain, and the nobles of Zeng State might even have authority to supervise certain area extending to Jiujiang. As lead isotopes of the bronzes appear to show a clear relation to chronology, the change of lead isotope patterns across times may further serve to distinguish the bronzes of the Western Zhou dynasty from the late Shang ones.

Material Investigation of Bronze Artefacts from the Late Bronze Age

The study deals with the material survey of a raw material, bronze axe and sickle from the Late Bronze Age. Artefacts were chosen from a set of about thirty objects, which were found in a ceramic pot near to Křenovice in the South Bohemia. The ancient technology of the axe and the sickle production was determined by the evaluating of structural properties using prepared metallographic sections. The chemical composition of a metal matrix and intermediate phases were determined using a scanning electron microscope with an EDS analyzer and X-ray fluorescence. The corrosion products of the artefacts were analyzed by X-ray diffraction. The results showed that the axe was made from partly wrought bronze (CuSn10) processed by subsequent recrystallization annealing. The bronze sickle (CuSn11) was a cast without any further mechanical processing or heat treatment. The material of the a raw material was found to be an arsenical copper alloy (CuAs1), which was probably used as a starting material for the bronze alloy production.

Copper-ore mining in Sweden since the pre-Roman Iron Age: lake-sediment evidence of human activities at the Garpenberg ore field since 375 BCE.

Historical documents, archaeological evidence and lake-sediment records indicate thus far that significant mining of iron and copper ores in the Berglsagen mining region in central Sweden did not begin until the late 12th century – first with iron in Norberg – and thereafter spreading rapidly throughout the region during the 13th century when also copper was included (e.g. Falun). Prior to this, iron was produced domestically from secondary sources such as bog iron, while geochemical analyses of bronze artefacts indicate copper was imported. The parish of Garpenberg was at the intersection between historical iron- and copper-mining districts, and consequently we expected our sediment record from the lake Gruvsjön (‘mine lake’) to follow the established 13th century development. However, a 2–3-fold enrichment in copper and lead occurred already during 375–175BCE (pre-Roman Iron Age), together with small increases in zinc, magnesium and charcoal particles, and changes in pollen. Together these indicate a clear pattern of human disturbance connected with the ore body bordering the lake. A second distinct phase occurred 115–275CE, but with an 8–9-fold increase in copper and lead along with other indicators. From 400CE a permanent increase in copper and lead occurred, which then accelerated from the 13th century as seen elsewhere in the region. Our results push back the evidence for early ore mining in Sweden from the Middle Ages to the pre-Roman Iron Age.