Corrosion and Conservation of Ancient Metals

In bibliografia l'attività di microscavo raramente viene affrontata dal punto di vista metodologico, ma diviene spesso funzionale, solo come mezzo, alla messa in luce di un manufatto di particolare rilievo o complessità. L'intervento qui esposto si propone, attraverso l'esperienza di studio svolta su tre blocchi di terra contenti reperti metallici, provenienti da una tomba etrusca datata al periodo Orientalizzante, di individuare e descrivere una metodologia univoca applicabile a stacchi contenenti oggetti o frammenti anche di materiali diversi. Attraverso l'analisi di casi noti in letteratura si è cercato di mettere appunto una metodologia che impiegasse in maniera ottimale i dati ottenuti delle indagini analitiche preliminari, quali la tomografia computerizzata multistrato e la radiografia X, come anche la documentazione fotografica prodotta durante tutta la fase di lavoro. L'impiego di questi dati uniti all'individuazione di alcuni aspetti chiave relativi all'attività pratica di scavo, ha permesso di mettere appunto una prassi operativa da applicare univocamente ai tre casi studio. Sviluppi futuri di questo lavoro saranno legati all'applicazione della metodologia proposta su altri casi in maniera da ulteriormente valutarne limiti e implementarne i punti di forza.

Analysis of the effectiveness of conservation methods of iron archaeological artefacts: examples from the Przeworsk culture in Kamieńczyk, Nadkole and Oblin
After analysing conservation documentation created during the last thirty years, carried out by the Conservation Department of the State Archaeological Museum in Warsaw, it was noticed that a group of iron archaeological objects repeatedly returned to the Conservation Department for treatment. It was decided to take a closer look at this problem.
This project presents, inter alia, the results of research on the impact of specific conservation methods applied over many years at DKM PMA to maintain the stability of iron artefacts. The basis of the analysis is a collection of objects of Przeworsk culture from the sites in Kamieńczyk, Nadkole and Oblin, which are part of the collection of the State Archaeological Museum in Warsaw. The material originating from them is consistent both in archaeological and conservation terms. These sites  are the cemeteries of the Przeworsk Culture from the area of Mazovia, functioning since the end of the second century BC - A2 phase (only Nadkole begins to function slightly later, from the second half of the 1st century BC - A3 phase) to the second half of the second century. - B2 / C1 phase. Archaeological excavations in the area were carried out by PMA employees, and documentation and material collected during the excavation is stored and processed at the museum. In addition, there is full conservation documentation regarding these artefacts. As a result, it can be noticed that similar methods were used to preserve objects from the discussed positions. The total number of iron artefacts from these three sites (about 2000) is a representative group in relation to the whole collection of PMA conserved iron objects.
Analysis of the object  complexes from Kamieńczyk, Nadkole and Oblin is carried out on the basis of a database created for the needs of this project. It contains information that allows identification of conserved artefacts as part of the PMA collection, as well as data on conservation procedures for individual items. As part of the latter group, information was gathered on the methods of stabilization, cleaning, materials used for cleaning, consolidation, strengthening and protecting the surface, as well as corrosion inhibitors. These data were then subjected to a detailed analysis, which allowed to answer questions about the effectiveness of individual methods. But also determine the position of the conservation process in the hierarchy of factors affecting the stability of iron archaeological objects. Artefacts are usually complex systems of relationships between metal and corrosion, and the state of their behaviour during normal "use" and storage in museums can be very different from the condition of experimental samples in accelerated aging tests. Therefore, it seems necessary to conduct research on the effectiveness of methods and means used for conservation, and to confront their results with information available in the literature. In addition, the research results presented in this project are aimed at deeper understanding of the needs of the collection belonging to the State Archaeological Museum, defining the threats and determining the priorities for managing its conservation. At the same time, the author hopes that the conducted research will be helpful for other Polish museums that have iron archaeological relics in their collections.

The presented work primarily focuses on both the damascene
and patination technique which are archaeometallurgically
treated within the framework of the Bronze Age
north of the Alps. The aspect of patination is here perceived
as a pure artificial procedure. On the one hand the investigation
should reveal how damascenings were realized on
bronze objects and if the observations provide evidence for
clarifying the provenance of the rarely used inlay technique
– a major question that is still unsolved. On the other hand
authentic methods are to be examined in detail that once
presumably allowed the patination of prehistoric damascened
items for enhancing the weak color contrasts between
base metals and inlays.
First of all the study shows that metal inserts were not
used frequently throughout the whole Bronze Age and in
the different areas north of the Alps. There were longer
gaps between the various stages of the era. In contrast platings
as a special form of damascening (»surface damascening
«) were applied continuously since period Montelius
II, yet this decoration is only a characteristic feature for the
Nordic circle that was not adopted in southern regions.
Using only electron as decoration metal throughout the
entire Bronze Age platings differ from damascenings with
metal inlays (»inlaid damascening«) in another point that
besides gold or electron they mainly availed of unalloyed
copper. Later the spectrum of inlaid damascenings was
enlarged by pewter, bronze, and iron. The investigation
demonstrates furthermore that the cavities for inlays on
most objects were already designed prior casting. However,
multiple evidence is found for reworking cast grooves. Only
in some cases the grooves were made exclusively by chasing
or engraving.
For Late Bronze Age artifacts it becomes clear on account
of stylistic and technical characteristics that the metal inlay
technique was practiced only by few workshops, nevertheless
probably having influenced each other. Such considerations
are much more difficult to proof for the Early and
Middle Bronze Age as there are less damascened pieces. Yet,
similar decoration patterns and techniques suggest interactions
between single craftsmen or workshops. Unfortunately,
the provenance of the damascene technique still
remains unclear despite this new investigation. Though, it
is at least unlikely that the polychrome decoration was
directly adopted from Mediterranean or even Greek prototypes,
but the stimulations rather have to be searched in the
Carpathian region. Finally, also a selfcontained development
somewhere in Central or Northern Europe cannot be
completely ruled out.
On the basis of patination experiments it can be shown
that in fact human urine is suitable for coloration of damascened
objects with copper inlays. Ideally, the medium produces
purple-black patinas on unalloyed copper while the
addition of elements such as tin or arsenic to copper gives
somewhat lighter appearances. High concentrations of tin
result in light yellow or slightly green-gray coatings. Even
these colors may have been desired in prehistory on tin
bronzes as they perfectly contrast with purple-blackish
patinated copper inlays. The investigated method therefore
emerges as a possible and formerly neglected way for patinating
many damascenings of the Bronze Age north of the
Alps. For this, however, some preconditions have to be fulfilled
which are discussed in detail in the following work.

A bronze sculpture of Mars, the Roman God of War, was found at Zeugma in the course of the 1999-2000 excavation campaign. It undoubtedly represents one of the most interesting and spectacular finds discovered so far in this city on the banks of the Euphrates, in southern Anatolia, Turkey. In the brief presentation below, some preliminary information about the sculpture and its discovery will be provided, as well as an overview of current operations for its conservation and restoration. It is hoped that the statue will be ready for public viewing at the end of 2002.

Ce mémoire propose d’envisager une utilisation des carboxylates de sodium pour la stabilisation de la corrosion réactivée des alliages cuivreux. La démarche suivie consiste à en évaluer le potentiel à travers les données bibliographiques et la réalisation de tests, par comparaison avec le benzotriazole. Les études sur alliages cuivreux sains et peu corrodés mettent en avant la formation d’un film protecteur en surface, aux propriétés hydrophobes, susceptibles d’apporter une isolation des chlorures. Pour vérifier si ce composé pouvait se
former en présence d’un faciès de corrosion réactivée, le décanoate de sodium a été testé en tubes à essai sur différents substrats, celui-ci ayant montré le meilleur potentiel pour la
stabilisation. Une action particulière en présence de chlorure cuivreux a été observée par la formation d’un composé. Face à ces résultats, des essais ont été entrepris directement sur des fragments d’alliages cuivreux archéologiques, soumis à une corrosion réactivée. L’utilisation potentielle du décanoate de sodium est estimée à travers l’évaluation de son efficacité
stabilisatrice relative et des modifications induites par le traitement sur les strates de corrosion et l’aspect de surface. Même si les résultats démontrent une efficacité satisfaisante,
l’utilisation du décanoate de sodium ne peut pas être envisagée suite à ces tests, à cause du problème des modifications de l’aspect de surface, qui n’a pas pu être résolu par une
diminution du temps d’immersion. D’autres solutions doivent donc être tentées pour rendre ces composés applicables à la stabilisation des alliages cuivreux.

This report was written in order to describe in detail the restoration
processes involved in my end of year examination project. It contains theoretics and a detailed description of the practice processes used.
The piece in analysis is 15th century armour, which is located in the
Military Museum of Lisbon. The building of the Museum, remounts to the 13th century, when the Arsenal of the Army was established. Having undergone several transformations, it reaches the present as the Military Museum with one of the most prestigious national assets, to which the armour belongs.
The armour is composed of alloy of iron (steel). However, it presents
some elements in copper alloy (brass) for ornamental ends and a leather strap is
used for the support.
The complete armours were shown in innovation as regards to defensive
equipments in the 15th century. However, two centuries later they start to decline
with the new combat tactics, turning to parade pieces, which were still used in the19th century.
Today as many museum pieces, they are not exempt from natural
deterioration.
The piece in analysis revealed several weakened areas at the surface level
unchained by the chemical and physical reaction when the material is exposed to atmospheric agents, causing several pathologies.
In sequence, in the study of the pathologies and based on the ethics
in conservation and restoration, the intervention focused on the cleaning of all the exposed corroded areas of the surface of the piece and stabilizing it with a protector layer.
The proposed objectives are accomplished in the final results of the
intervention, with the certainty that the piece will, henceforth, have the longevity its heritage values deserve.

Con este trabajo se pretende realizar una revisión de los tratamientos y técnicas de conservación y
restauración utilizados en los últimos años sobre objetos de cobre y sus aleaciones, así como las técnicas empleadas
para el control de dichas intervenciones, el testado de nuevos productos y el uso de nuevos materiales.

Die 138 römischen Siegelkapseln aus Augusta Raurica bilden den bisher grössten publizierten Komplex eines einzelnen Fundortes dieser relativ seltenen Fundgattung. Siegelkapseln dienten meist zum Verschluss von Schreibtäfelchen und zur Absicherung ihres geschriebenen Inhalts vor unbefugten Augen.
Der erste Teil dieses Buches behandelt die Typologie, den Katalog mit den Kapiteln zur Verwendung, Aufbau, Datierung, Verbreitung und Kulturgeschichte der Siegelkapsel. Im mittleren Teil werden die zahlreichen Beobachtungen an Werk- und Herstellungsspuren vorgelegt. Im dritten Teil folgen naturwissenschaftliche Untersuchungen sowie Archäometrie, Untersuchung der verwendeten Materialien und Sedimentanalysen aus dem Inneren der Kapseln.
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Comprehendsive analysis of 138 Roman seal boxes from Augusta Raurica. They constitute the largest complex of this quite rare find category published to date from a single site. The vast majority of seal boxes served to lock writing tablets and to protect the written contents from prying eyes.
The first part of this book deals with the archaeological evidence and the typology of seal boxes, the catalogue with chapters on use, construction, chronology, distribution and cultural history of the seal boxes. The second part is concerned with the examination of the traces of manufacture and technology. The third part of the publication is dedicated to various scientific analyses, namely archaeometry and study of materials used as well as analysis of sediment contents of selected seal boxes.

This paper deals with the term ‘patina’ and the difficulty in defining a priori those materials that should be preserved on a metal surface. Dogmatic and restrictive ideas exist that only patinas, understood as visually pleasant corrosion, should be preserved. This has resulted in treatment criteria that have promoted the loss of important technological, historical and aesthetic information and materials. These comments arise from observation of damage to the sculpture of the Spanish king Carlos IV, known as El Caballito, in Mexico due to a non- professional treatment that caused losses to its surface. This paper proposes the term ‘surface layer’ to identify, describe and assess all materials on a metal surface, especially metal sculptures, irrespective of their nature, intention, origin, temporality or function. The term encourages the understanding that different materials on a metallic surface can be worthy of preservation, even if they do not correspond to a patina.

Many scientists have through time developed interests in undertaking researches related either directly or indirectly to corrosion, which could be attributed to increasing cases of material breakdown as a result of corrosion. There are therefore several published works focused on studies of the corrosion behavior and mechanism of various metals in several different environments or media. In this review paper, we explored and analyzed the various recent research works on corrosion kinetics using weight loss method, and to a certain extent about corrosion inhibition.

For decades, the conservation of archaeological iron has challenged conservators. A variety of techniques have been used in an attempt to mitigate the negative effects of chloride ions on the corrosion of iron artifacts and prevent deterioration. This article briefly reviews important milestones in the history of iron conservation as well as major issues regarding treatment and stabilization. Current iron conservation research undertaken at the newly formed Clemson Conservation Center, home of the H.L. Hunley submarine (1864) in Charleston, South Carolina is also discussed.

A technical study was conducted on a group of copper alloy artifacts excavated from the burial tumulus of Lofkënd (fourteenth–ninth century BCE) to identify the alloy compositions and methods of manufacture. The surface corrosion was also examined in order to understand the diagenetic processes affecting the preservation of the finds and their condition. Portable X-ray fluorescence spectroscopy, metallographic examination, and X-ray powder diffraction (XRD) analysis were used to characterize the alloy composition and identify the corrosion products present. XRD analysis showed the presence of brochantite (Cu4SO4(OH)6) on five of the metallic artifacts. Brochantite is not commonly reported on archaeological bronzes from terrestrial sites, but is more readily found on copper alloy objects exposed to sulfur pollutants in the air or soil. The possible conditions that could have led to the formation of this corrosion on the bronzes from Lofkënd are discussed in the context of the particular burial environment found at the tumulus.

When restoring the metal artefacts which may be linked with a Langobard ethnic group, found in site 2 during excavations preceding construction of the M86 motorway, the greatest problem was the advanced state of corrosion, which significantly slowed down restoration. The objects had very little core metal, in certain cases none at all. The interpretable shapes, by which the objects may be typologised, were preserved by the corrosion, so after removal of the earthy contamination from the surface, only mechanical interventions could be performed on them for the most part. During restoration, the iron objects had to be kept in one piece by constant sticking and solidification. In a number of cases remnants of wood could be discovered on the artefacts and samples were taken of these.
Az M86-os autóút megelőző feltárása során, a 2. lelőhelyen előkerült, germán népcsoporthoz köthető fémleletek restaurálásakor a legnagyobb problémát az előrehaladott korróziós folyamatok jelentették, amelyek jelentősen lassították a helyreállítást. A tárgyak nagyon kevésfémmaggal rendelkeztek, bizonyos esetekben pedig egyáltalán nem. Az értelmezhető formákat, melyek alapján a tárgyak tipologizálhatók, a korrózió őrizte meg, ezért a földes felületi szenynyeződések eltávolítása után, többnyire csak mechanikus beavatkozásokat lehetett elvégezni rajtuk. Restaurálás közben a vastárgyakat folyamatos ragasztással és szilárdítással kellett egyben tartani. Több esetben sikerült famaradványokat felfedezni a leleteken és mintát venni belőlük.

The presence or absence of use-wear marks on copper (Cu)-alloy weaponry has been used since the late 1990s to investigate the balance between functional (combat) and symbolic (value, status, religious) use of these objects, and thus explore their social and economic context. In this paper, we suggest that this work has not taken sufficient account of the material properties of Cu-alloys. We discuss mechanisms of plastic deformation, incremental repairs and corrosion in detail to show how these can obscure use-wear traces. In a survey of Cu-alloy weaponry from the Nordic Bronze Age (1800/1700e550 BCE) from Denmark, Sweden and Germany, we show that corrosion of Cu-alloy objects is strongly linked to depositional context, being greater in burials (both inhumations and cremations) than hoards or as single objects. A relative paucity of use-wear marks on burial weapons should therefore not be used to argue that these were purely symbolic objects, e.g. in contrast to the better preserved hoard material. We propose that use-wear traces on Cu-alloy weaponry, particularly on blade edges, is significantly more elusive than previously realised, and that undamaged objects have been over-identified.

A group of bronze artifacts produced and traded by Urartians(900-700 BCE), one of the most advanced stage of mining and industry of the ancient world, exhibited in the Rezan Has Museum are investigated in 2011-2014 under the sponsorship of Bank of America&Merrill Lynch: The Art Conservation Project. Employing the minimum intervention techniques, of today, this study aims to maintain the preservation states provided by the remarkable choice of ancient technologies and composits. In this context the corrosion products have been indentified by using Raman Spectroscopy and X-Ray Diffraction techniques and evaluated togather with hand held X-Ray Flourescence Spectroscopy results before and after mechanical cleaning procedure.

""The metalworking, metal import, and use of metal in medieval Iceland is still little understood. When the Scandinavian settlers colonized Iceland in the 9th c. AD, the island was found to contain no useful metal deposits save for bog iron, and the deforestation that followed the settlement resulted in a scarcity of wood. Only in the last decades have archaeological excavations begun to unravel how the first Icelanders dealt with this lack of resources. This paper presents the metallurgical findings from a Viking Age chieftain’s farmstead at Hrísbrú in the Mosfell valley, located just outside Iceland’s present-day capital Reykjavik. The excavated metal objects had all been crafted with good orkmanship employing technology similar to that used in mainland Scandinavia. However, most excavated metal finds show evidence of re-use, which together with the second-grade metal in some of the objects indicates a shortage of raw material that prompted the Icelandic colonizers to improvise and make do with whatever material was at hand.
Even though this chieftain’s farm was materially poorer than contemporaneous high-status farms in mainland Scandinavia, it was wealthy by Icelandic standards. The analytical results show that some excavated objects were imported trade goods deriving from both neighboring and far-away localities, proving that the farm was part of the extensive trade network of the Viking world. Most likely, this farm represents the upper limit to what a Viking Age farm in Iceland could afford in terms of material objects and trade goods.""