Raman analysis of glaze on various archaeological shard samples and intact Ming plates

Abstract

Raman microscopy is used in the analysis of glaze on a number of samples that include blue and white ceramic shards, a tile from the Citadel of Algiers and intact Ming plates. The use of the glaze depth profiling method for the study of interfacial pigments on these samples [J. Raman Spectrosc. 2007; 38: 1480] prompted the study of the glaze on the same set of samples to determine glaze type dependence of this method. Using the index of polymerization (Ip) which is closely correlated with glaze composition and processing temperature, it is shown that processing temperature could be estimated from a low of about 600 C for some of the unknown archaeological shards to about 1000 C or above for the Ming porcelain shards. Two intact porcelain plates from the Hongzhi (1488 – 1505) and Wanli (1573 – 1620) Ming imperial periods from the J. A. van Tilburg Museum of the University of Pretoria have been studied, and glaze/glass transition temperature was estimated to be above 1000 C, consistent with historical data. A SnO2-based glaze tile shard from the Citadel of Algiers was also successfully probed, and results indicated a much lower sintering temperature.