Apply over fired glaze to add brilliant accents that’ll make your project look like a billion bucks! Overglazes are an accent product that are applied over a fired glaze and then kiln fired to a relatively low temperature. They are sometimes referred to as "third fire" glazes. Mother of Pearl is a luster, an overglaze; it is applied over a shiny fired glaze of any color. (Copper glazes should not be used). Any natural hair brush will work, it should be clean. Apply MOP in swirls, just one thin coat. You want to see brushstrokes; they will be the swirls in the finished piece. Fire to cone 020.