Influence of BaO/CaO Ratio in Glaze on Color and "Color Dispersion" of Blue-and-white Porcelain

Blue-and-white porcelain is the essence of traditional Chinese ceramic culture. However, during the preparation and firing of blue-and-white porcelain, due to the influence of the formula composition and preparation process of the blue pigment, uneven coloration occurs in the blue and white decoration, while the lines of the blue and white decorative materials may show varying degrees of “color dispersion” (the length of the spread of blue and white decorative lines is called "color dispersion"), resulting in blurred outlines and lines in the blue and white picture, which destroys the bright, clear and layered expression effect of blue and white. In order to identify the reasons for this phenomenon, this paper is aimed to explore the influence of BaO/CaO ratio in the glaze on the coloration and "color dispersion" behavior of blue-and-white porcelain, thereby revealing the effect of the glaze layer structure on the coloration mechanism and "color dispersion" behavior of blue-and-white porcelain.

To clarify the extensive color variations and the "color dispersion" phenomenon of blue-and-white porcelain, the effects of the BaO/CaO ratio in the glaze on the chromaticity value, "color dispersion" distance, microstructure, glaze network structure and Co²⁺ concentration, in the glaze of blue-and-white porcelain, were analyzed using field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), electron probe microanalysis (EPMA) and optical microscopy (OM).

It is experimentally demonstrated show that, as the BaO/CaO ratio in the glaze increases, the strength of the Si-O-Si bonds in the glaze network structure decrease, while the "color dispersion" distance of the blue-and-white porcelain lines first increases (60–100 μm). However, when the BaO/CaO ratio is increased to 1.71, stable octahedral Co-spinel crystals exist in the reaction layer at the interface between the blue pigment and the glaze, whereas the "color dispersion" distance decreases to about 60 μm, while the b* value first increases (-33.65 to -29.38) and then decreases to -33.1.

With increasing ratio of BaO/CaO in the glaze, the strength of the Si-O-Si bonds in decreases. The viscosity of the glaze decreases, while the "color dispersion" distance of the blue-and-white porcelain increases. However, when the ratio of BaO/CaO reaches 1.71, stable Co-spinel crystals exist in the interface layer of the blue-and-white porcelain, whereas the "color dispersion" distance of the blue-and-white porcelain decreases again. Therefore, it is concluded that the size of the "color dispersion" distance of the blue-and-white porcelain is related to the viscosity of the glaze and the stability of the crystal structure of the blue pigment. The result lays a solid physical and chemical foundation for the technological development of blue-and-white porcelain decoration and points out the direction of development.