Stability of Malayaite Pigments in High-ZnO Ceramic Glazes

This study examined the chemical stability of malayaite pigments in ceramic glazes containing high amounts of zinc oxide (ZnO). The calcined pigments were embedded in a molten glaze which is basically corrosive glass. Within the glaze, ZnO has been known among potters to be undesirable as some pigments are not stable in glazes containing ZnO. The synthesized pigments’ particle size ranges from 4 to 18 μm without dominant preferential orientation. Their colors were in the red and yellow tones. Chemical stability between the pigments and glazes was tested using X-ray Diffraction (XRD). Slight changes were observed. Increasing amounts of ZnO resulted in an interfacial layer of approximately 50 μm between the crystalline pigment and surrounding amorphous glaze. The a color parameters gradually decreased while the b parameters switched to a negative value. The resulting glazes evolved from maroon to pale violet. The correlation between color and microstructural alterations was discussed.