image database: CuAs-alloys

Following the links below, you can find images of cross-sections of different Cu-As alloys. In the upper right corner, you have the indication for the percentage of Arsenic, followed by the indication of annealing time (in min.), the amount of deformation (in %), and the magnification (the bars with the indication of size are in a separate image). Just ignore ‘quer’ or ‘copy’ in the filename. The samples were first deformed (and yes, it is possible to deform CuAs-alloys up to 98% without cracking!), and then annealed. All samples are cross-sections.

To give you an example: Image ‘1As_20min_40def_quer_100x_3 copy’ means that a sample of CuAs-alloy with 1 wt.% As was 40% deformed and afterwards annealed for 20min. The magnification is 100x.

Here is the overview of samples and treatment:

  • Chemical composition: 1, 2, 3, 4, 5, 10 wt.% As
  • deformation (cold rolling): 0, 20, 40, 60, 80, 98%
  • annealing time: 0, 20, 40, 80 min at 600°C in reduced atmosphere
  • After annealing, the samples were quenched in water.

Images (follow the links):

…be patient with the scratches: The alloys arereally soft after annealing and it wasn’t a pleasant experience to polish these samples!

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It’s spring again and there are still a lot of pigeons in Vienna…

An alternative usage of arsenic as described by Georg Kreisler  (information in English) in his black humour chanson ‘Tauben vergiften‘ [poisoning pigeons] due to the high number of pigeons in Vienna in the 1950ies.

Tauben vergiften

Schatz, das Wetter ist wunderschön
Da leid ich’s net länger zu Haus
Heute muss man ins Grüne gehn
In den bunten Frühling hinaus!
Jeder Bursch und sein Mäderl
Mit einem Fresspaketerl
Sitzen heute im grünen Klee –
Schatz, ich hab’ eine Idee:Schau, die Sonne ist warm und die Lüfte sind lau
Gehn wir Tauben vergiften im Park!
Die Bäume sind grün und der Himmel ist blau
Gehn wir Tauben vergiften im Park!
Wir sitzen zusamm’ in der Laube
Und ein jeder vergiftet a Taube
Der Frühling, der dringt bis ins innerste Mark
Beim Tauben vergiften im Park

Schatz, geh, bring das Arsen gschwind her

Das tut sich am besten bewährn
Streu’s auf a Grahambrot kreuz über quer
Nimm’s Scherzel, das fressen’s so gern
Erst verjag’mer die Spatzen
Denn die tun’am alles verpatzen
So a Spatz ist zu gschwind, der frisst’s Gift auf im Nu
Und das arme Tauberl schaut zu

Ja, der Frühling, der Frühling, der Frühling ist hier
Gehn wir Tauben vergiften im Park!
Kann’s geben im Leben ein größres Plaisir
Als das Tauben vergiften im Park?
Der Hansl geht gern mit der Mali
Denn die Mali, die zahlt’s Zyankali
Die Herzen sind schwach und die Liebe ist stark
Beim Tauben vergiften im Park…
Nimm für uns was zu naschen –
In der anderen Taschen!
Gehn wir Tauben vergiften im Park!

GMPCA conference, Rennes – Poster

AccueilDuring the last days, I have been at the 21st international GMPCA conference in Rennes, France, listening to a lot of very interesting papers. The conference is THE conference for ‘archaeometrists’ in France and a fantastic opportunity to meet colleagues and researchers of all fields of archaeometry. Together with Benjamin Sabatini I presented a poster on Chemical and metallurgical aspects of arsenical bronze: inverse segregation in prehistoric Cu-As objects. You can find the poster for download here.

Getting used to arsenic

A recent publication in the American Journal of Physical Anthropology describes how humans adapted to arsenic in Andean populations of the Atacama Desert. It is here, where the highest arsenic levels in the Americas are found (>1,000 µg/L). The local population though, the Camarones people, who live in this environment during the last 7,ooo years, have not presented any epidemiological emergencies.

So the authors of the study – Mario Apata, Bernado Arriaza, Elena Llop and Mauricio Moraga fom the Universidad de Chile in Santiago and the Universidad de Tarapacá – compared the frequencies of four protective genetic variants of the AS3MT gene associated with efficient arsenic metabolization, between the living populations of Camarones and two other populations historically exposed to lower levels of arsenic. They found higher frequencies of the protective variants in those people from Camarones than in the other two populations.

The higher frequency of protective variants in both northern Chilean populations indicates a long exposure to naturally arsenic-contaminated water sources. The data suggest that a high arsenic metabolization capacity has been selected as an adaptive mechanism in these populations in order to survive in an arsenic-laden environment.

However, one has to note that a third of the population does not have any of the protective genetic variants of the AS3MT gene and still does not show any significant signs of arsenicosis – further research is planned (or maybe they should visit Styria?).

(for further info, see the article here).

Colour measurements of copper alloys

CIELAB coordinates (SCI) with error bars (standard deviation: 2σ) of different arsenical bronze alloys.

CIELAB coordinates (SCI) with error bars (standard deviation: 2σ) of different arsenical bronze alloys.

The color characteristics of different copper alloys of particular interest in archaeometry (Cu-As, Cu-Sn, Cu-Sb, Cu-Ni) are investigated quantitatively and systematically. By using the CIELAB color system, different color parameters such as a*, b*, and L* were measured by a spectrophotometer in order to describe the surface color. This permits the establishment of a set of color-composition diagrams, demonstrating clearly the connection between chromaticity parameters and alloy composition.

With the evaluated data it is possible to start thinking about the role of color in technological choice, because it allows us to estimate the color of prehistoric metal artefacts with comparable compositions. A better understanding of the association between metallurgical alloy and color will aid the research of prehistoric metalwork because choices in production and use of metal were likely influenced by the particular qualities the material had to offer, of which color is an important one.

The article, which has as co-authors Daniel Berger and Maikel Kuijpers, was submitted recently and will be hopefully published soon. I keep you updated!

Late Bronze Age Caucasian daggers made of arsenical bronze… and tin bronze

Several Late Bronze Age Caucasian daggers were studied in order to evaluate their chemical composition and microstructure. The daggers derive from North Ossetia-Alana, Russia, and are since the 1880ies in the Natural History Museum Vienna. The arsenical bronzes are characterised by a high amount of arsenic (2-5wt.%), as are the tin bronzes by high amounts of tin in the alloy (10-17 wt.%). However, most of the dagger blades studied are ternary Cu-As-Sn alloys. Two arsenical bronze blades show intense segregation of γ-phase along the blades’ surface and the grain boundaries (remember my article on inverse segregation of arsenical bronzes!); some of the arsenical bronze blades also show eutectic, which hardness could be measured. One dagger was made of a tin-bronze blade and an arsenical bronze hilt (see Figure on the bottom). The article will include chemical analyses, metallographic studies, hardness measurements, and Pb-isotope analyses. I’ll keep you updated once it’s published!

Late Bronze Age dagger from Koban, Republic of North Ossetia-Alania, Russia. The colour of the hilt was silverish while the blade had a warm, golden-like colour. The hilt contains about 9.8 wt.% arsenic and no tin, while the blade contains 10.1 wt.% tin, and no arsenic. Today, the dagger is very much corroded, so the original colours of the metals are not any more visible (Photograph © Naturhistorisches Museum Wien; inv.no. 41.268).

Late Bronze Age dagger from Koban, Republic of North Ossetia-Alania, Russia. The colour of the hilt was silverish while the blade had a warm, golden-like colour. The hilt contains about 9.8 wt.% arsenic and no tin, while the blade contains 10.1 wt.% tin, and no arsenic. Today, the dagger is very much corroded, so the original colours of the metals are not any more visible (Photograph: M. Mödlinger, © Naturhistorisches Museum Wien; inv.no. 41.268).

Hardness measurements of different Cu-As phases

Caucasian dagger blade made of arsenical bronze with 4.5 wt.% As; the hardness of the eutectic could be detected.

Caucasian dagger blade made of arsenical bronze with 4.5 wt.% As; the hardness of the eutectic could be detected.

Finally, all samples are polished, so I can start with hardness measurements. Here, I would like to thank especially Fabrizio Barberis, DICCA,  and Armanda Barbangela, DIME, both Università degli Studi di Genova, for the possibility to carry out all hardness measurements with them. In that way, I was able to use both a purely mechanic, historic instrument, and could carry out also μHV measurements on my arsenical bronze alloys, as well as on Late Bronze Age daggers from Koban. The publication of the analyses of the daggers is currently in preparation, and will include chemical analyses, metallographic studies, hardness measurements, and Pb-isotope analyses.