Reactive glaze is a type of glaze that undergoes a chemical reaction during firing, creating a unique pattern or color. The glaze is made from different raw materials, including organic, mineral, or metallic elements, and then applied to the pottery piece after biscuit firing. The glaze is then smooth-fired, which results in an unpredictable finish. This means that no two pieces of reactive glaze pottery are identical, and each piece has a distinct appearance with features like blemishes, dimples, aesthetic cracking, and unevenness to the touch.