Study On The Production Process And Deterioration Mechanism Of Glazed Shadow Wall Of Chenghuang Temple And Wenmiao Temple In Hancheng City,Shaanxi Province

Glazed shadow wall has a rather important position in China’s architectural glazed components,and is a concentrated embodiment of glazing production techniques and architectural culture.There are 18 glazed shadow walls from the Ming and Qing dynasties preserved in Hancheng City God Temple and Wenmiao Temple in Shaanxi Province,which have great scientific,artistic and cultural values.However,due to their long-term preservation in an open-air environment,almost all of the glazed shadow walls have deteriorated to different degrees,which has seriously affected their integrity and aesthetics.Therefore,in this thesis,we use X-ray diffraction,scanning electron microscopy-X-ray energy spectrometry,ion chromatography and other scientific research methods to study the production process and deterioration mechanism of the glazed walls of Hancheng Chenghuang Temple and Wenmiao Temple.We hope to provide theoretical support for the restoration work later.The research shows that the glaze is made of low-temperature lead-glazed pottery with a secondary firing process.It is composed of four parts:body,glaze,make-up clay and gray seam.The clay used is made of local loess with high Ca content.Green glaze,yellow glaze and brown glaze belong to the traditional Chinese low-temperature lead glaze PbO-SiO₂-Al₂O₃ system.Peacock blue glaze belongs to PbO-SiO₂-alkali glaze（K₂O and Na₂O）system.The cosmetic clay is made of clay with high refractoriness.After refinement,the cosmetic clay has a high whiteness.In addition,it is presumed that the potters innovatively introduced high potassium mineral raw materials into the make-up clay.Gray seam is a lime mortar commonly used in ancient Chinese architecture,and the main component is calcium carbonate.The main diseases of the shadow wall glaze are glaze adhesion,glaze cracks and peeling,glaze corrosion and tarnish-alkali weathering,of which glaze adhesion can be subdivided into three categories:soluble salt,black crust and yellow attached particles.We analyze the causes,formation process and deterioration products of each disease in shadow wall glaze.It is found that the soluble salts on the glaze surface are mainly CaSO₄.Na₂SO₄ and a small amount of NaCl,and the repeated crystallization and dissolution of the soluble salts eventually lead to the weathering of the body.The black crusts on the glaze surface are mainly composed of CaSO₄,CaCO₃,CaSO₄·2H₂O,and some of the crusts have layered conditions.The yellow adhesion on the glaze surface is mainly composed of gypsum and quartz,in addition to a certain amount of hematite.The glaze corrosion products are mainly PbSO₄,PbSO₄·2PbO and Pb₅（PO₄）₃Cl.each color glaze deterioration degree is different,among which green glaze and peacock blue glaze corrosion is the most serious,yellow glaze and brown glaze exist slightly deterioration phenomenon.It has been studied that the combination of raw material formulation and natural environment of shadow wall glaze makes it appear various diseases.