Petrographic Analysis of Ancient High-Temperature Ceramic Glazes and Inorganic Restoration Materials

Abstract

ABSTRACT The application of scientific and technological studies prior to the repair of historic and ancient ceramics can provide a more complete understanding of glazes to aid the conservator's decision-making process before undertaking the conservation of ceramics. There are two categories of Chinese glaze morphology for general high-temperature single-color glazes, calcium glazes (smooth glazes), and calcium alkali glazes (glazes containing more bubbles or crystals and multiple glazes). High-temperature colored glazes can be divided into four types: on-glazed, in-glazed, diffused, and under-glazed pigments. The subdivision of high-temperature glaze types has significance as a guiding factor in the repair of historic and ancient ceramic glazes. Optical coherence tomography (OCT) is discussed as a non-invasive way to understand glaze structure and as a tool to aid the conservator in the treatment of ceramics. Moreover, a silica sol-acrylic composite coating was studied as a possible material to use in the replication of ceramic glazes on areas of restoration. A small amount of acrylic resin can improve the reversibility of the synthetic coating. On the macro level, this coating exhibits natural glaze bubbles and craquelure similar to historic and ancient ceramics; in addition, on the micro level, it can imitate the clean calcium glaze and crystallization calcium alkali glaze of such ceramics. The silicon oxide content in this glaze-like material is found to be similar to that of historic and ancient ceramics.