1 research outputs found
Medieval Gilding Technology of Historical Metal Threads Revealed by Electron Optical and Micro-Raman Spectroscopic Study of Focused Ion Beam-Milled Cross Sections
Although gilt silver threads were
widely used for decorating historical
textiles, their manufacturing techniques have been elusive for centuries.
Contemporary written sources give only limited, sometimes ambiguous
information, and detailed cross-sectional study of the microscale
soft noble metal objects has been hindered by sample preparation.
In this work, to give a thorough characterization of historical gilt
silver threads, nano- and microscale textural, chemical, and structural
data on cross sections, prepared by focused ion beam milling, were
collected, using various electron-optical methods (high-resolution
scanning electron microscopy (SEM), wavelength-dispersive electron
probe microanalysis (EPMA), electron backscattered diffraction (EBSD)
combined with energy-dispersive electron probe microanalysis (EDX),
transmission electron microscopy (TEM) combined with EDX, and micro-Raman
spectroscopy. The thickness of the gold coating varied between 70–400
nm. Data reveal nano- and microscale metallurgy-related, gilding-related
and corrosion-related inhomogeneities in the silver base. These inhomogeneities
account for the limitations of surface analysis when tracking gilding
methods of historical metal threads, and explain why chemical information
has to be connected to 3D texture on submicrometre scale. The geometry
and chemical composition (lack of mercury, copper) of the gold/silver
interface prove that the ancient gilding technology was diffusion
bonding. The observed differences in the copper content of the silver
base of the different thread types suggest intentional technological
choice. Among the examined textiles of different ages (13th–17th
centuries) and provenances narrow technological variation has been
found