Understanding the blue color in antique mosaic mirrored glass from the Temple of the Emerald Buddha, Thailand

Abstract

Two samples of the blue glass produced in the middle 19th century from the Temple of the Emerald Buddha in Bangkok, Thailand, were studied in order to understand the origin of its blue color. The oxide components and trace elements are quantitatively determined by scanning electron microscopy coupled with energy‐dispersive and wavelength‐dispersive spectrometry and laser ablation inductively coupled plasma mass spectroscopy techniques. The results identify the glass type as soda‐lime‐silica glass with high lead content. The 3d transition elements detected include iron, manganese, cobalt, and copper. Combined analyses of X‐ray absorption near edge structures and optical absorbance lead to a conclusion that the antique glass is primarily colored in blue by the divalent cobalt with additional yellow coloration as a result of the trivalent iron. The tetrahedral coordination geometry of these two species was deduced from the XANES pre‐edge intensity and the optical absorption bands of their d‐d transitions. The redox ratios of Fe2+/Fe3+, Mn2+/Mn3+, and Cu1+/Cu2+ in the original blue glass and the reference glasses were determined by the K‐edge XANES analysis. The blue color of the antique glass can be reproduced in a laboratory glass on the basis of composition and melting conditions. Copyright © 2015 John Wiley & Sons, Ltd.