Medieval nanotechnology: Thickness determination of Zwischgold samples

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

“…Hence, given some foreknowledge of the sample composition, the identity of a material can be inferred from the measured local δ values, together with variations in composition and/or porosity. 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.…”

“…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.…”

Thin thickness gilding determined by x‐rays ratios from EDXRF‐spectra

“…Of these, only SEM directly measures the gilding thickness. All others indirectly determine the thickness 2–7 . Energy‐dispersive X‐ray fluorescence (EDXRF), a well‐established analytical technique in archaeometry, multielemental and fast, is preferable, nondestructive, and noninvasive.…”

Nondestructive Microanalysis of Thin-Film Coatings on Historic Metal Threads

“…Several types of decorative metal threads have been defined and described in literature, ,, including solid metal threads made of thin (10–50 μm) flattened metal strips, which were either used directly, or wrapped around a core of silk, cotton, or other fibers. , Solid gold was the first metal used to adorn textiles, but as technology developed, gilt (Au coated) silver came into popular use in Europe during the 12–13th centuries, followed by other metal combinations such as brass-coated copper. , Various technologies for depositing metal coatings (e.g., diffusion bonding, fire gilding, and depletion gilding) have origins that can be traced back to the late fourth or early third millennium BCE. Gilding methods were readily available to produce layers with micro- and nanoscale thicknesses, providing the desired color and luster appearance at reduced costs. ,− As such, techniques used to analyze metal threads must be capable of submicrometer depth resolution to characterize their composition and microstructure. ,− …”

“…These previous studies are predicated upon threads gilded with pure Au, and as a result, they are not suitable to address thin films of more diverse chemistry [e.g., Au alloys, brass, bronze, or zwischgold (Au/Ag bilayer foil)]. ,− Since ancient times, Au has been alloyed with Ag and Cu to control color, workability, and cost . Alloys have been reported as early as 862 BCE, where the inhabitants of Lydia (modern day Turkey) were minting coins of 73% Au 27% Ag .…”