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Studied gombiky. A From Mikulčice. B From Prague Castle, Lumbe´s garden cemetery. A a- gombik 76/š, grave 290-3rd church; b-gombik 129/š, grave 420b-2nd church; c-gombik 190/š, grave 550-3rd church; d-gombik 217/š, grave 625-3rd church; e-gombik 220/š, grave 662-3rd church; f-gombik 110/z, grave 498-3rd church; g-gombik 115/z, grave 508-3 rd church; h-gombik 117/z, grave 508-3 rd church; i-gombik 255/š, grave 43-6th church; j-gombik 26/z , grave 91-2nd church; k-gombik 45/z, grave 141-2nd church. B a-gombik H 104-4; b-gombik H 115-8; c-gombik H108-2; d-gombik H84-1; e-gombik H104-3; f-gombik H99-5; g-gombik H 74B-2; h- gombik H 53-14
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Gilded copper hollow spherical pendants known as gombiky (s. gombik) were examined to identify the technology of gilding and the material chosen as the substrate. The examined ornaments dating from the ninth and tenth centuries AD were recovered from elite graves of two major political, ecclesiastical and economic centres of the Early Medieval peri...
Citations
... Therefore, the study of unearthed cultural relics is no longer limited to the morphological observations or compositional analysis of the golden surface (Ingo et al. 2007). Instead, it goes deep into the interior of the cultural relics to study the compositional distribution and structural characteristics of the cross-section and the interface between the gold layer and the substrate (Ottenwelter et al. 2020), revealing the forming mechanism of the gold layer during the gilding process . It is worth mentioning that the heating causes phase change of Au-Hg amalgam during the gilding process, thereby forming a gold layer (Jin et al. 2017). ...
Compared with other gold plating processes, mercury gilding was widely used in ancient China due to the less consumption of gold and excellent adhesion between the gold layer and substrate. Herein, the comprehensive analyses of the silver crown and boots unearthed from the Consort Tombs of Emperor Shengzong (圣宗萧贵妃) of the Liao (辽) Dynasty reveal the surface composition and structural characteristics and also the unique multilayered structure and cross-sectional compositional distribution of the gold layer. First, the existence of mercury on the golden surface of cultural relics, as well as the unique porous structure and granular surface morphology, indicate that the artifacts were probably processed using mercury gilding. In addition, the intermetallic compound, i.e., Au5Hg, in the gold layer indicates that the processing temperature was 388–419 ℃; thus, the formation mechanism was the transformation of solid solution in the amalgam to intermetallic compound during the heating of Au-Hg system. Moreover, the cross-sectional transition layer is mainly composed of Ag and Hg due to the interstitial diffusion of mercury atoms at room temperature and vacancy diffusion of silver atoms during the heating process, bonding the gold layer with the substrate. Obviously, the bonding mechanism of the gold layer and substrate was interstitial diffusion and vacancy diffusion within the Ag-Hg system. The current work reveals the special multilayered cross-section of silver gilding relics and shows that mercury played a crucial role in both the formation of the gold layer and bonding between the gold layer and substrate during the silver gilding process.
... The study focuses on central European gilded copper jewellery, for which fire gilding was largely applied (Ottenwelter, in press). It concerns the fire gilding layers of specific archaeological artefacts found in Bohemia (Lumbe Garden cemetery at Prague Castle): gombiky (spherical hollow pendants) and medallions, characteristic pieces of the elite jewellery from the 9th and 10th centuries AD, detailed in previous studies (Ottenwelter et al., 2014;Ottenwelter et al., 2017;Ottenwelter et al., 2020;Ottenwelter, in press). The use of FIB FEG-SEM allows crosssections to be made and observations performed in situ within the SEM (Johnson et al., 2012;Chiavari et al., 2015;Masi et al., 2016, Masi et al., 2017. ...
... (i) The fragment of gombik H84-1 is a sample from a large gombik (total length: 55.6 mm, diameter: 44 mm - Fig. 1a) its construction is typical of Bohemian pieces, as shown from X-ray radiography (Fig. 1e): a two-hemisphere body and a suspension system made of three components (Ottenwelter et al., 2014;Ottenwelter et al., 2017;Ottenwelter et al., 2020): a loop, a clamp and a ring, in this case also including a small pellet inside the soldered hemispheres. The gombik was highly fragmented when excavated. ...
... In addition to the size of the artefact and the decoration type, which are the basic parameters of comparison, the technical consideration enables the identification of fine products produced by highly skilled and knowledgeable jewellers operating in a courtly environment, and coarse imitations produced by local and less experienced craftsmen (Ottenwelter et al., 2020;Ottenwelter, in press). This technical consideration is mainly linked to the mounting concept, the choice of material (base material, gilding layer, type of solder), the quality of the mounting, soldering, gilding, tool marks as well as the quality of the decoration. ...
The study of ancient gilding is often problematic, as the gilding layers are soft and prone to deformation during sample preparation. In this respect, focused ion beam (FIB) milling on a field emission gun scanning electron microscope (FEG-SEM) provides poorly invasive in situ sampling. The operating process is here detailed and applied on gilded medieval copper-based elite jewellery (10th century) from Prague Castle. Obtained cross-sections and slices of gilded samples were investigated up to nanometer scale without gilding layer deformation. By coupling structural observation with elemental X-ray analysis (EDS) and electron beam diffraction (EBSD), FIB FEG-SEM provided new data on the physical–chemical characteristics of the gilded layer. The gilding has a two-layer metallurgical structure containing a quaternary Au (Hg, Cu, Ag) alloy corresponding to the gold solid solution fcc phase, and a submicrometric inner sublayer formed by a Au-Cu phase, relative to the interdiffusion of copper from the substrate during the fire gilding process. The applied temperature for gilding can be estimated at c. 400 °C. Sintering of the mercury-gold amalgam globules during the fire heating is highlighted. The precise characterisation of the gilding layers provided useful comparative parameters for identifying fire gilding skill levels and assessing the overall quality of the archaeological pieces.
