| Autor: |
Wu Q; University of Zurich (UZH), Rämistrasse 73, 8006 Zurich, Switzerland.; TH Köln - University of Applied Sciences, Ubierring 40, 50678 Köln, Germany. qingaling@gmail.com., Soppa K; Bern University of Applied Sciences (BUAS), Fellerstrasse 11, 3027 Bern, Switzerland. karolina.soppa@hkb.bfh.ch., Müller E; Paul Scherrer Institute (PSI), Forschungsstrasse 111, 5232 Villigen-PSI, Switzerland. elisabeth.mueller@psi.ch., Müller J; Micro- and Nanoanalytics Group, Universität Siegen, Paul-Bonatz-Strasse 9-11, 57076 Siegen, Germany. julian.mueller@uni-siegen.de., Odstrcil M; Paul Scherrer Institute (PSI), Forschungsstrasse 111, 5232 Villigen-PSI, Switzerland. elisabeth.mueller@psi.ch.; Carl Zeiss SMT, Carl-Zeiss-Straße 22, 73447 Oberkochen, Germany., Tsai EHR; Paul Scherrer Institute (PSI), Forschungsstrasse 111, 5232 Villigen-PSI, Switzerland. elisabeth.mueller@psi.ch.; Brookhaven National Laboratory, Upton, New York 11973, U.S.A. etsai@bnl.gov., Späth A; Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Egerlandstraße 3, 91058 Erlangen, Germany. andreas.spaeth@fau.de.; Institut für Nanotechnologie und korrelative Mikroskopie (INAM), Äußere Nürnberger Strasse 62, 91301 Forchheim, Germany., Holler M; Paul Scherrer Institute (PSI), Forschungsstrasse 111, 5232 Villigen-PSI, Switzerland. elisabeth.mueller@psi.ch., Guizar-Sicairos M; Paul Scherrer Institute (PSI), Forschungsstrasse 111, 5232 Villigen-PSI, Switzerland. elisabeth.mueller@psi.ch., Butz B; Micro- and Nanoanalytics Group, Universität Siegen, Paul-Bonatz-Strasse 9-11, 57076 Siegen, Germany. julian.mueller@uni-siegen.de., Fink RH; Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Egerlandstraße 3, 91058 Erlangen, Germany. andreas.spaeth@fau.de., Watts B; Paul Scherrer Institute (PSI), Forschungsstrasse 111, 5232 Villigen-PSI, Switzerland. elisabeth.mueller@psi.ch. |
| Abstrakt: |
Many European sculptures and altarpieces from the Middle Ages were decorated with Zwischgold, a bilayer metal leaf with an ultra-thin gold face backed by silver. Zwischgold corrodes quickly when exposed to air, causing the surface of the artefact to darken and lose gloss. The conservation of such Zwischgold applied artefacts has been an obstinate problem. We have acquired quantitative, 3D nanoscale images of Zwischgold samples from 15 th century artefacts and modern materials using ptychographic X-ray computed tomography (PXCT), a recently developed coherent diffractive imaging technique, to investigate the leaf structure and chemical state of Zwischgold. The measurements clearly demonstrate decreasing density (increasing porosity) of the leaf materials and their corrosion products, as well as delamination of the leaves from their substrate. Each of these effects speak to typically observed issues in the conservation of such Zwischgold applied artefacts. Further, a rare variant of Zwischgold that contains extremely thin multiple gold layers and an overlapping phenomenon of Zwischgold with other metal leaves are observed through PXCT. As supportive data, scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray analysis (EDX) were performed on the medieval samples. |
