Identification of ancient gilding technology and Late Bronze Age metallurgy by EDXRF, Micro-EDXRF, SEM-EDS and metallographic techniques

Abstract

A combination of analytical techniques capable of elemental and microstructural characterisation was used for the identification of ancient gilding technology and bronze metallurgy. EDXRF, micro-EDXRF, SEM-EDS analysis and metallographic examinations were applied in the study of artefacts dating to the end of the second millennium BC from Crasto de São Romão in Central Portugal. Results report to the finding of an exceptional gilded copper nail among bronze artefacts with 9 wt.% to15 wt.% tin and minute other metallic impurities. Additionally, analysis of a crucible fragment points out for bronze production at the archaeological site. EDXRF and micro-EDXRF analysis made on the copper nail showed that it was gilded only on the front side of the head, and that the gold layer has been lost in the most exposed areas. SEM-EDS analysis showed that the gold layer has 5-8 µm in thickness and is covered with a thick corrosion layer. The gilding technique is discussed based on the gold layer composition and gold/copper substrate interface. So far, this object seems to be the first diffusion gilded artefact identified in the Portuguese territory dated to Late Bronze Age.

Nondestructive Techniques in the Study of a Gilded Metallic Sword From the Islamic Art Museum

“…The cohesion between the gilding and the base alloy was damaged, suggesting either the use of a quite durable adhesive or that some diffusion among the metals has taken place. Any mechanical attachment would most likely lead to the formation of a strong corrosion among the two metals, in the same way as the use of a less durable organic adhesive that would easily decay under burial [16,20]. The brass alloy (copper and zinc alloy) commonly has 30% Zinc.…”

“…Optical microscopes are able to provide a wide range of information on metallurgical features and conservation state of the objects; and the metallographic approach can be considered easy to apply, a flexible research tool [16]. Microscopic observations were made on a Smart-Eye USB Digital Microscope at various magnifyications between 100 X and 200 X, and the microstructures on the surface were studied under a Stereo microscope -a Zeiss (stemi 508) imaging binocular microscope (50x-200x magnification), with both visible and fluorescent lights, and an AxiocamERc 5s digital camera.…”

Identification of metal residues associated with bit-use on prehistoric horse teeth by scanning electron microscopy with energy dispersive X-ray microanalysis

“…SEM/EDX is a nondestructive technique that can be used to quantify chemical element compositions at the surfaces of archaeological materials (e.g. Ferrer-Eres et al, 2010Figueiredo et al, 2010). It is applied here in the identification of metal residues associated with bitting on Iron Age horse teeth.…”

Characterisation of Late Bronze Age large size shield nails by EDXRF, micro-EDXRF and X-ray digital radiography

“…Generally, the recent archaeometallurgical studies on metallic artefacts from that region have shown the prevalence of a binary bronze (Cu-Sn alloy) metallurgy with 9-15% Sn and minor and variable amounts of Pb, As and Sb (Figueiredo et al, 2006(Figueiredo et al, , 2010aSilva et al, 2008;Valé rio et al, 2006Valé rio et al, , 2007, and the sporadic use of copper to produce specific items when the properties of this metal were an advantage (e.g. Figueiredo et al, 2010b). In that region, and during the first half of the XX century, six exceptional large size nails, a dagger and a sickle (Fig.…”

“…Besides, it can also provide information about special features such as the presence of composite artefacts (e.g. Cesario et al, 2010;Figueiredo et al, 2010b). After, micro-EDXRF analyses were performed in two small areas free of the superficial patina in one of the nails, in order to obtain quantitative information on the metallic composition.…”