Study On Jian Series Black-glazed Bowls And The Corrosion Products Dated Back To Song Dynasty

Research on corrosion of archaeological porcelain has rarely been carried out in the past.Jian series black-glazed porcelains in Song Dynasty was the the epitome of the Chinese black-glazed ceramic art,which was famous for their amazingly textural patterns in glaze,such as "Hare's Fur"(HF),"Oil Spot"(OS)and "Yohen" patterns.A group of black-glazed bowl sherds,which excavated from the Luhuaping Jian kiln site of Fujian province and the Xiaowan Tushan kiln site of Chongqing city,were found in a poor conversation,thus they were investigated.On the basis of understanding the chemical composition and phase composition of glaze of different samples,it is found that glaze is mainly affected by soil and water in burial environment.The initial corrosion process are all the hydrated process and ion-exchange process,then different corrosion behaviors occur according to the composition of samples and the outside solution:in the black glaze,the anorthite crystallization zone will preferentially react with water in comparison with glass phase,leading to the embrittlement of the anorthite zone.After the ion-exchange reaction between glass phase and water,a kind of silicon-rich hydrated gel is formed.The gel would shrink to generate the gel layer,pits or cracks under various conditions.As the glaze had complex phase compositions,different phases underwent different corrosion kinetics.Some of the heterogeneous phases had better stability(except for anorthite),thus the inter-diffusion rate was slower in this region and part of them left in the alteration crust.As a result,the alteration layer with uneven thickness formed.In addition,the dissolution of-Si-O-Si-network structure of glass phase can also lead to cracks and continue to increase the corrosion area.Besides,special acicular silica crystals were found in alteration products for the first time,which were different from the homogeneous glass.The complex compositions and structures in black glaze had a special impact on the alteration layer.The study presented the information of the environment which black-glazed porcelain exposed to and revealed relevant historical information,thus to provide guidance for their conservation.At the same time,it also has reference significance for the corrosion study of other types of ceramic relics.