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Study of gold alloy productions from Late Bronze Age and Iron Age
Publication . Serrano, Sofia Pereira; Figueiredo, Elin; Silva, Rui
This master’s dissertation focuses on the archaeometallurgical study and conservation
of thirteen gold alloy earrings attributed to the Late Bronze Age and Iron Age from
the Western Iberia. Most of the artefacts studied are from the collection "Treasures of
Portuguese Archaeology" of the NationalMuseum of Archaeology (Lisboa, Portugal). Based
on typological and decoration features, they were divided into two groups: eight plain
gold rings, attributed to the LBA, which are bulk objects with a smooth surface, and five
IA earrings with complex goldwork, like gold wires, sheets, granules and gilding.
The aim of the study includes: i) the study of the alloy compositions; ii) the study of
the detailed fine goldwork of the objects; iii) contribute to the understanding of technological
evolutions from LBA to IA; iv) determination of heterogeneities in gold alloys at
the surface level, due to corrosion, technological features or previous treatments, with
an influence on their conservation. To achieve these goals complementary analytical and
examination techniques were used, such as general photography, multifocus microscopy,
elemental analysis by portable and micro X Ray Fluorescence Spectrometry (XRF) and microscopy
and elemental analysis by Scanning Electron Microscopy with Energy Dispersive
Spectroscopy (SEM-EDS).
Results showed variations on the artefacts composition, being mostly composed by an
Au-Ag alloy (8-20 wt.% Ag), with small amounts of Cu. The only exception are two IA
earrings, with absence of Cu, unusual for alloys from this period. It also allowed to carry
out compositional characterizations at different depths, concluding that heterogeneities
exist within surface areas but can be more significant at different depths. Overall, a
superficial loss in Ag was found, possibly due to corrosion phenomena, being that any
conservation and restoration treatment could interfere with the final surface composition.
It was found that the goldwork performed in some earrings is very fine, showing that
ancient goldsmiths were able to produce wires and granules with less than 1 mm in
diameter, as well as gilding. The results obtained are significant for the study of ancient
technologies as well as for future conservation approaches to Proto-historic goldworks.
Study of a late bronze age casting mould and its black residue by 3D imaging, pXRF, SEM-EDS, micro-FTIR and micro-raman
Publication . Figueiredo, Elin; Bottaini, Carlo; Miguel, Catarina; Lackinger, Aaron; Mirão, José; Rey, Beatriz Comendador; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); MDPI - Multidisciplinary Digital Publishing Institute
In the present work, a fragment of a stone mould recently found in Galicia (NW Spain) was studied by multiple analytical techniques approach involving 3D optical imaging reconstruction to obtain data about the shape of the mould, typology of artefact produced, and distribution of a black residue at the surface of the mould and pXRF, SEM-EDS, micro-FTIR, and micro-Raman to investigate the nature of the black residue. The study shows that the mould was likely used for socketed axes with a side loop, was originally composed of two valves and one core, and that it might have been subjected to a repair during use. The black residue is distributed in the carved surface and spreads to nearby surfaces as a result of the use of the mould. The alloy cast in the mould was a ternary bronze (Cu + Sn + Pb). The analyses by SEM-EDS of black residue covering the surface did show the presence of scattered micro particles with P and Ca, and micro-Raman analysis detected the presence of a carbon black of animal source, while micro-FTIR analysis detected remains of proteins, oxalates, and hydroxyapatite. These results are amongst the very few studies made on black residues of ancient moulds and suggest that the mould was dressed with a carbon black of animal origin, such as burned bones, prior to metal casting, probably used as a coating agent to improve the casting and artefact recovery.
Contributions to the study of corrosion and Conservation strategies of archaeometallurgical collections: An approach through Outeiro de Batar (Spain) and Castanheiro do Vento (Portugal)
Publication . Silva, Gabriel de Sousa Nunes da; Figueiredo, Elin
This study focuses on archaeological metallurgical collections related to copper metallurgy, their conservation and better understanding of their corrosion, which is the pathology that most often affects archaeological metal artifacts. Two archaeological collections were studied: the archaeological collection of Castanheiro do Vento (Guarda, Portugal) and the archaeolog-ical collection of Outeiro de Baltar (Ourense, Spain). On the first collection the corrosion of the copper alloys was studied through stereomicroscope observation and XRD analysis, through which it was possible to identify Cu I compounds (Cuprite) and Cu II compounds (malachite). An organization with the development of specific labels, tags and storage solutions was de-veloped so that the collection can maintain its integrity and which were considered of most importance for any future archeometallurgical study and future museum storage. The Outeiro de Baltar archaeological collection was studied through samples that were prepared for a de-tailed microstructural analysis to better understand its corrosion characteristics, only the cop-per (bronze) alloys were studied. The collection was studied through optical microscopy ob-servation, micro-EDXRF, and SEM-EDS analysis. Influence of the type of thermo-mechanical work as well as various aspects of typical corrosion of archaeological copper alloys were ob-served, such as corrosion depth variances, presence of δ-phase, copper sulfides, lead inclu-sions, selective corrosion of δ-phase (observed in a high-tin bronze), unalloyed copper inclu-sions and silver inclusions.
Conservação e restauro de peças de ferro e de liga de cobre da Necrópole do Senhor dos Mártires no Museu Nacional de Arqueologia
Publication . Ferreira, Francisco de Almeida; Figueiredo, Elin; Santos, Margarida
Neste relatório de estágio desenvolveu-se uma abordagem interdisciplinar, com a finalidade de estudar e preservar 15 peças selecionadas da coleção de artefactos arqueológicos metálicos da Idade do Ferro, provenientes do sítio arqueológico da Necrópole do Senhor dos Mártires, em Alcácer do Sal, Setúbal, que integram atualmente as reservas do Museu Nacional de Arqueologia. Para o desenvolvimento deste estágio, foi pretendido uma intervenção rigorosa, cruzando as áreas das ciências humanas e ciências exatas, de forma a alcançar valores defendidos pelo ICCOM e instituições museológicas. Para tal, realizou-se uma metodologia que inclui (i) a caraterização elementar das peças por Fluorescência de Raios X por-tátil (p-XRF), (ii) o estudo dos materiais através de pesquisa bibliográfica de forma a entender a compatibilidade e as propriedades dos diferentes materiais, (iii) determinar o melhor tratamento de conservação para as caraterísticas únicas de cada peça e (iv) executar ações de conservação e restauro. Foram executadas intervenções de conservação e restauro em 9 peças de ferro e em 6 de liga de cobre, incluindo peças de armaria e adorno, nomeadamente numa falcata, em lanças, numa fíbula e em fechos de cinturão. Algumas destas peças apre-sentam decoração com folhas e lâminas finas de diversos materiais, como cobre e prata, descobertas durante as intervenções, e que implicaram adaptações nos procedimentos de conservação e restauro.
Tin and Bronze Production at the Outeiro de Baltar Hillfort (NW Iberia)
Publication . Figueiredo, Elin; Rodrigues, Alexandra; Fonte, João; Meunier, Emmanuelle; Dias, Filipa; Lima, Alexandre; Gonçalves, José Alberto; Gonçalves-Seco, Luís; Gonçalves, Filipe; Pereira, Manuel F. C.; Silva, Rui J. C.; Veiga, João P.; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; DCR - Departamento de Conservação e Restauro; MDPI - Multidisciplinary Digital Publishing Institute
Findings of Iron Age metallurgical activities related to tin metal and mining are very rare. In the present work, we present a detailed study of the Outeiro de Baltar hillfort, dated to the Late Iron Age/Early Roman period, located in a place where 20th century tin mining work took place. Elemental and microstructural analysis by portable, micro and wavelength dispersive X-ray fluorescence spectrometry (pXRF, micro-XRF and WDXRF) and scanning electron microscopy with energy dispersion spectrometer (SEM-EDS) showed that metallurgical debris found at the archaeological site is related to tin smelting and binary and ternary bronze productions. Analysis of the artefacts of diverse typologies found at the site showed that a variety of metals and alloys were in circulation and use. Samples of tin ores (cassiterite) from the region were analyzed for comparison with an archaeological tin slag from the site. The analytical results point to the production of tin metal using local cassiterite and the production of bronze by directly adding cassiterite into a smelting process. Furthermore, data of remote sensing (airborne Light Detection and Ranging (LiDAR) and historical aerial imagery) and Geographical Information System (GIS) mapping were combined with archival mining documentation and maps to retrieve a landscape context for the site. The study showed that the place of the Outeiro de Baltar hillfort (NW Iberia) was mined periodically over time.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
9471 - RIDTI
Número da atribuição
PTDC/HAR-ARQ/32290/2017