Study on the copper and iron coexisted coloring glaze and the mechanism of the fambe

With copper and iron oxides as colorants, reddish and bluish purple glazes were prepared by changing the raw material ratio at the same firing schedule. Based on the primary factor experiments and the analyses of XRF and SEM/EDS, the fambe mechanism was proposed. The results indicated that glaze colors were related to multiple factors. The difference in copper red and purple glazes was merely caused by the later ingredient containing Ca₃(PO₄)₂, in which liquid-liquid phase separation structures were developed and formed structural colors, while the accumulated Fe₂O₃ in one phase decomposed to Fe²⁺ and bubbles to form blue stains and colorful texture. In addition, both CuO and Fe₂O₃ had a variety of coloring characteristics, which depended on the process parameter, firing temperature and base glaze compositions to make colors and hues change accordingly. In such cases, the multiple chemical colors were coupled with structural colors to form the fambe glaze.