Characterization of Gold Thin Films Deposited by Centuries-old Fire-gilding Method

Abstract

We have explored the centuries-old fire-gilding method which is being practiced by craftsmen in Nepal. In this technique, gold films are deposited on metal by heating the paste of gold amalgam layer coated on the metal surface. Samples of gold thin films deposited on copper substrate by this traditional method were characterized by x-ray diffraction (XRD) for structural properties, and atomic force microscopy (AFM) and scanning electron microscopy (SEM) for surface morphology. The XRD pattern of the samples showed the formation of polycrystalline gold film on the copper substrate. Microstructure characterization of the surface morphologies from the AFM and SEM images showed the gold films have porous feature with submicron size pores. We also performed optical reflectance measurements of the gold films deposited by this method to investigate the effects of double coating of gold amalgam layers, burnishing process and iron oxide treatment on the gold film. We found that the optical reflectance is increased as the surface smoothness is increased by double coating and burnishing. We also found that the vivid golden luster is enhanced by iron oxide treatment due to increased reflectance in the red spectral region.