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 substances—and then applied to the pottery piece after biscuit-firing. The glaze is then smooth-fired, which results in a distinctive finish that can't be predicted. This means that no two pieces of reactive glaze pottery are identical, and each piece has a one-of-a-kind appearance with features like blemishes, dimples, aesthetic cracking, and unevenness to the touch.