Why must ceramic pigments be chemically inert when used in glazes?

Ceramic pigments used in glazes must be chemically inert to ensure stability during the firing process. When a glaze is applied to a ceramic body and refired, the glaze formulation undergoes vitrification to create a smooth, impermeable surface.1

If the pigments were not chemically inert, they could react with the molten glass-forming components of the glaze or the underlying ceramic body during this high-temperature process. Such reactions would lead to unwanted changes in color, texture, or the structural integrity of the finish. By remaining inert, these pigments maintain their intended aesthetic properties and ensure that the glaze remains consistent and durable once cooled.21