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Characterisation of metal threads and metal thread manufacturing methods

All metal thread samples included in the MODHT project consist of metal filaments wound around a silk core. A previously unnoticed correlation of thread diameter and metal strip width with coils per unit length has been established. Rare double and triple wrapped metal threads have also been identified.

Energy Dispersive X-ray microanalysis (EDX) showed 6 to 12 wt % copper in the silver bulk of most samples, suggesting European origin of manufacture. Out of 16 gilt metal threads analysed only one showed double-sided gilding of the metal filament. This was surprising as, according to the literature, the manufacturing dates of the tapestries lie within the transitional period of two manufacturing techniques. Namely, 'beaten and cut' and 'cast, drawn and rolled', the latter resulting in a double-sided gilding, the former leading to single sided gilding.

New information on manufacturing techniques was obtained by Field Emission Gun Secondary Electron Microscopy (FEG-SEM) of single sided gilt metal filaments in longitudinal- and cross-section, which produced evidence of the metal being cut but rolled rather than hammered, suggesting a combination of manufacturing techniques. Gold layer thicknesses were measured to ~ 100-300nm. FEG-SEM images also revealed evidence for a leaf gilding technique.

Related information

Reported by

The University of Manchester
School of Materials
United Kingdom
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