Műtárgyvédelem, 2011 (Magyar Nemzeti Múzeum)
Gherdán Katalin - Weiszburg Tamás - Ratter Kitti - Zajzon Norbert - Bendő Zsolt - Varga Gábor - Szakmány György: A soproni Kecske-templomban feltárt sírlelet körgallérjáról származó fémfonalak mikro- és nanoléptékű morfológiai és kémiai vizsgálata
Műtárgyvédelem 36 Micro- and Nanoscale Investigation of Metal Threads Decorating a Women’s Attire from the Goat Church Sopron Katalin Gherdán - Tamás Weiszburg - Kitti Ratter - Norbert Zajzon - Zsolt Bendő - Gábor Varga - György Szakmány The basic aim of this study was to specify the manufacturing techniques, especially gilding methods, of certain metal thread types used for decorating the cape. On the basis of the findings of previous studies (see Járó and Tóth in this volume), attempts were made to answer the following questions: 1. What microtexture, nanotexture, and layer structure do the threads exhibit, and how thick is the gold coating? 2. Is there any chemical enrichment at the gold/silver interface indicating the gilding technique? 3. How do gilded and non-gilded silver strips relate to each other with regard to texture and composition? The fine texture of the examined strips and wires was exposed by using focused ion beam (FIB) milling. The cross-sections created were subjected to high resolution SEM + EDX and EPMA analysis. The threads were mounted on tilted (at 45°) sample holders, and after the depositing of platinum on their gilded surfaces, FIB ion milling was used to make cross-sections. This analytical procedure proved to be very efficient in distinguishing between the possible gilding methods. When trying to identify gilding techniques, the morphology of the surface gold coating and the geometry of the gold/silver interface were examined, along with related changes in chemical composition. Owing to the perfect fitting between platinum and gold, it was possible to measure the thickness of the gold coatings (0-255 ± 5 nm). Geometrically, the gold/silver boundary was sharp. In the case of the drawn wire, there were finger-like intrusions of the gold into the silver base metal, while in samples with a strong vertical component of subsequent manufacturing (post-gilding hammering, rolling) a smooth gold/silver boundary line could be seen. At the gold/silver interface, no enrichment of elements indicating the gilding technique (Cu: use of a copper-based soldering material; Hg: fire gilding) was found. Based on this observation and sources describing contemporary gilding technologies, it can be stated that metal threads used for decorating the cape were gilded by welding. It was found, however, that strips gilded on one side only had a different composition and nanotexture. The copper content of such strips was about twice as much as that of the wires. Cross-section texture analysis showed that this elevated copper concentration was caused by the use of a different (copper-enriched) silver base metal rather than by the gilding technique (the use of a copper-based soldering material). This phenomenon might reflect intentional technological difference. This was the first time that ion milling (FIB technique) combined with high- resolution SEM and EDX, WDX analysis provided an opportunity to investigate 70
