Investigation of the foil structure and corrosion mechanisms of modern Zwischgold using advanced analysis techniques

A modern look at a medieval bilayer metal leaf: nanotomography of Zwischgold

“…The main materials of interest, namely the metallic Au and Ag, are expected to be observable in peaks located at δ-values of approximately 40 × 10 −6 and 25 × 10 −6 , while the main corrosion products (i.e., Ag 2 S and AgCl) are expected to be significantly porous and so should produce peaks at δ-values lower than the 17.6 × 10 −6 and 13.6 × 10 −6 calculated from their respective bulk densities. Previous EDX measurements 15 and complementary XPS measurements (see Fig. S16 †) confirmed the dominance of Ag 2 S in the 35-year sample and therefore the peak centred at 15 × 10 −6 is attributed to Ag 2 S. Since this Ag 2 S peak position has a δ-value approximately 15% lower than expected for the bulk material, we conclude that the observed material has a 15% decrease in density due to porosity below the resolution of this measurement.…”

“…This occurs because Ag atoms readily diffuse through the grain boundaries of the gold layer to reach the upper surface and then react with S and Cl in the presence of moisture. 14,15 In regions where the local guilds did not prohibit the use of Zwischgold, the application of a protective varnish was usually a requirement. 4,16 Since uncorroded Zwischgold applications are difficult to distinguish from gold leaf, it is probable that many Zwischgold examples remain unrecognised.…”

“…30 Due to its ultra-thin leaf thickness (e.g., 500-700 nm for modern Zwischgold 15 and significantly thinner for medieval Zwischgold 38 ), a characterisation of Zwischgold requires both high resolving power and high sensitivity and is thus challenging for conventional techniques. Recent work by our collaboration group 15,26,38,39 has demonstrated the use of modern analytical techniques such as SEM-EDX to identify and characterise modern and historical Zwischgold including its leaf structures and layer/leaf thicknesses, as well as its complicated individual ageing phenomena. These typically involve the formation of silver compounds that can be distributed evenly or in aggregates in regions surrounding the gold layer, and consumption of the silver base which leads to delamination of the metal leaf from the substrate.…”

Ion beam analysis of silver leaves in gilt leather wall coverings

“…All the silver leaves analyzed by RBS displayed a variability in thicknesses more or less important over a single leaf or area. Surface roughness and silver corrosion might have a role to play in this variability [21], however another factor should be considered, the presence of microporosities greatly smaller than the beam size in the metallic layer. Considering that the RBS spectrum obtained is an average of the materials encountered by the beam in each layer, if microporosities are present, the intensity of the peaks coming from the elements present in this layer will decrease, therefore reducing the calculated thickness.…”

Additive Nano-Lithography with Focused Soft X-rays: Basics, Challenges, and Opportunities

“…Since synchrotron-based X-ray microscopes offer continuously tunable excitation photon energy, it has been shown that within a multilayer of several photoresists consecutively stacked at the same spot, each layer can be addressed separately by the resonant photon energy of the respective Following the development of suitable focusing optics for soft X-rays [49][50][51], the first soft X-ray microscopes were installed in the mid-1980s [52,53]. Since then, STXM has developed into a versatile method for characterization of suitably thin specimens from various scientific disciplines, such as biology, medicine, catalysis, material science, magnetism, geology, cosmology, and cultural heritage [54][55][56][57][58][59][60][61][62][63][64]. Figure 1 depicts a scheme of a modern STXM with all basic elements and their respective degrees of freedom [59,65,66].…”