Microstructural characteristics of fifth-century Silla gilded artifacts from Hwangnam-dong Tomb No. 120-2 in Gyeongju, Korea

This study investigated the gilding microstructures and manufacturing techniques of a fifth-century Silla horse-harness fitting excavated from the grave-goods compartment of Hwangnam-dong Tomb No. 120-2 in Gyeongju, Korea. The specimen comprised two structural components: a gilded copper plate and a connecting iron rivet wrapped in gilded silver sheet. A single polished cross section prepared from the artifact was examined by stereomicroscopy, reflected-light metallurgical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Residual Hg in the gilded regions of both components supports the use of mercury-amalgam gilding. Gilding-related microstructures survived on both faces and at the bent ends of the silver sheet, consistent with gilding before wrapping the rivet. EDS analysis detected Au and Hg in the amalgam regions. High-magnification imaging revealed granular remnants at both ends of the rivet that may represent Au–Hg amalgam residues associated with incomplete finishing. Local gilding thicknesses at two locations on the copper plate were 1.33 ± 0.53 μm and 1.01 ± 0.23 μm, whereas the bright gilded regions on opposite faces of the silver sheet measured 3.69 ± 1.04 μm and 3.52 ± 0.63 μm. These measurements document local thickness differences between gilded regions on copper and silver substrates within one cross section. Together, the terminal granular remnants and substrate-associated differences in local gilding thickness provide evidence for reconstructing the gilding sequence and finishing practices employed in fifth-century Silla metalworking.