Close up to the Surface: Reflections on a Preliminary Forensic Study of Four Chinese Bronze Mirrors from a Hong Kong Private Collection

Abstract

This article presents an objective, evidence based, forensic study undertaken within the HKU Architectural Conservation Laboratory (ACLab) and Department of Physics conducted on 4 very different bronze mirrors from a private collection. They nominally cover the period from the Warring States (475-221BC), Han (206 BC to 220AD) and later Song (960-1279AD) dynasties. Comprehensive, mostly non-invasive, analytical methods and techniques were applied in this endeavour. These included surface microscopy of tool marks, patina, corrosion and any residual archaeological evidence. Ultraviolet radiation examination, chemical spot testing and polarised light microscopy of ground-up patina samples was also undertaken. More sophisticated “pXRF” X-ray fluorescence and “MARS” tomographic X- ray scanning analysis of the bronze alloy, corrosions and any earthen encrustations were also performed. This was all done to uncover as much forensic evidence as possible concerning these unprovenanced bronze mirrors. The combined results have revealed key metallurgical information of those four mirrors along with surface patina morphology and details of the corrosion and residual surface archaeology. A database on the physical condition of these 4 mirrors has been established and burial/treatment history revealed. Mirrors 1 and 2 appear to have been heavily cleaned, polished and treated with abrasives in modern times. Both of them but mirror 2 in particular have some problematic corrosion and inconclusive alloy composition. Mirror 3 and 4 both have archaeological evidence and no contrary forensic data that questions their authenticity. The issue of the possible authenticity of an object when archaeological context is lacking is discussed but this was not the ultimate goal of this research. The key aim is to establish what can be learnt from technological forensic investigation when studying bronze mirrors without archaeological context and records, and what firm evidence can be extracted from such close forensic examination to shed light on their true nature.