Why must ceramic pigments remain thermally stable during firing?

Ceramic pigments must remain thermally stable during firing because they are incorporated directly into ceramic bodies or glazes to impart specific colors to the finished ware.1

During the firing process, ceramic materials undergo high temperatures to achieve bonding and consolidation, often through a process known as vitrification, where crystalline compounds partially melt to form a glassy phase. Because pigments are subjected to these intense thermal conditions, they must possess both thermal stability and chemical inertness to ensure they do not degrade, react, or lose their intended color properties while the ceramic piece is being fired.21